NCERT Solutions for Class 6 Science (Dual Track: NEP 2020 & Classic CBSE)

Chapter 1: The Wonderful World of Science

NCERT Curiosity (Class 6) — Nature of Scientific Inquiry, Observation, Asking Questions, Hypothesis, Experimentation & Laboratory Safety | CBSE 2026-27

📌 Key Scientific Concepts & Principles

Nature of Science: Science is an organized, systematic way of exploring, understanding, and explaining natural phenomena around us through careful observation, experimentation, and logical reasoning.
Steps of Scientific Method:
- Observation: Noticing an interesting pattern or occurrence using our senses or measuring tools.
- Formulating a Question: Asking "Why?", "How?", or "What happens if...?" regarding the observation.
- Hypothesis: Proposing a tentative, testable explanation based on prior knowledge.
- Experimentation: Designing controlled trials with variables to test the hypothesis.
- Data Collection & Analysis: Recording measurements accurately in tables or graphs.
- Conclusion: Deciding whether the evidence supports or refutes the original hypothesis.
Branches of Science: Biology (study of living organisms), Chemistry (study of substances and their transformations), Physics (study of matter, energy, and forces), and Earth & Space Science (study of our planet and the universe).
Laboratory Safety & Ethics: Always wear safety goggles and lab apron, handle glassware gently, avoid smelling or tasting unknown chemicals directly, and dispose of wastes in designated containers.

Figure 1.1: The Iterative Scientific Inquiry Loop

NCERT Exercise 1.1: Foundations of Scientific Inquiry

What is science? Explain why curiosity and observation are considered the twin pillars of scientific discovery with suitable examples.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Definition of Science:
Science is the systematic pursuit and application of knowledge and understanding of the natural and physical world following a verifiable methodology based on evidence.

Role of Curiosity and Observation:

Curiosity (The Starting Spark): Curiosity is the innate desire to learn and understand. It drives a person to question why the sky is blue, how birds fly, or why milk curdles. Without curiosity, no scientific questions would ever be formulated.
Observation (The Evidence Collector): Observation involves carefully watching, listening, measuring, and noting down details of objects and events using our senses and scientific instruments.
Historical Example: Sir Isaac Newton observed an apple falling from a tree to the ground. Driven by curiosity regarding why the fruit fell straight down rather than moving sideways or upwards, he formulated the Universal Law of Gravitation.

CBSE Board Marking Scheme 2026-27

Clear definition of Science as a systematic body of knowledge1 Mark

Explanation of Curiosity and Observation as foundational steps1 Mark

Real-world or historical example (e.g., falling apple / gravitation)1 Mark

List the sequential steps of the scientific method. Why is a controlled experiment essential in testing a hypothesis?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Sequential Steps of the Scientific Method:
1. Making an accurate Observation.
2. Raising a well-defined Question.
3. Formulating an educated, testable Hypothesis.
4. Designing and executing a Controlled Experiment.
5. Recording and analyzing Data.
6. Drawing a logical Conclusion and communicating findings.

Importance of a Controlled Experiment:
In a controlled experiment, only one factor (the independent variable) is altered at a time while all other conditions are kept strictly constant. This ensures that any observed result is directly caused by the tested variable, eliminating accidental influences and bias.

CBSE Board Marking Scheme 2026-27

Stating all 6 steps in correct sequence1.5 Marks

Explaining importance of controlling variables to avoid false conclusions1.5 Marks

Figure 1.2: Standard Apparatus Used for Observations & Volume Measurements

NCERT Exercise 1.2: Laboratory Safety & Scientific Tools

State four important laboratory safety rules that every science student must follow while conducting experiments.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Key Safety Rules:
1. Wear Protective Gear: Always wear safety goggles, cotton lab coats, and closed shoes to protect eyes and skin from chemical spills.
2. No Tasting or Direct Inhalation: Never taste any substance in the lab. When checking an odour, gently waft the vapors towards your nose with your hand from a safe distance.
3. Safe Handling of Heat & Glassware: Always point test tubes away from yourself and classmates while heating over a spirit burner. Inspect glassware for cracks before heating.
4. Immediate Reporting: Immediately inform the teacher in case of chemical spills, accidental glass breakage, or skin contact. Wash affected skin thoroughly with abundant cold tap water.

CBSE Board Marking Scheme 2026-27

Listing four valid laboratory safety guidelines with scientific justifications0.5 Mark each (Total 2 Marks)

Differentiate between qualitative and quantitative observations with two examples of each. Which type of observation is preferred in scientific experiments, and why?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Qualitative Observation:
Observations described using words, characteristics, or sensory qualities without numerical measurements.
Examples: "The solution turned dark blue", "The leaf has a rough surface."

2. Quantitative Observation:
Observations described using measurable numbers, quantities, and standard units.
Examples: "The liquid volume is 250 mL", "The temperature increased by 5 °C."

Scientific Preference:
Quantitative observations are strongly preferred in scientific research because they are objective, exact, reproducible by other scientists worldwide, and can be statistically verified without personal interpretation bias.

CBSE Board Marking Scheme 2026-27

Accurate definition and distinction with examples2 Marks

Reason for preferring quantitative data (objectivity, precision)1 Mark

CBSE Competency-Based Question (Inquiry & Real-Life Case Study)

Case Study: Testing Seed Germination Conditions:
Aarav noticed that gram (chana) seeds kept in a dry container in the kitchen did not sprout, while seeds soaked in moist cloth germinated within two days. He decided to investigate the exact conditions needed for seed germination by setting up four test cups:
• Cup A: Dry seeds exposed to room temperature and sunlight.
• Cup B: Seeds completely submerged in water with oil layer on top (no air) at room temperature.
• Cup C: Seeds kept on moist cotton with access to air at room temperature.
• Cup D: Seeds kept on moist cotton placed inside a refrigerator at 4 °C.

(a) In which cup will the seeds successfully germinate? What was Aarav's hypothesis?
(b) What was the purpose of Cup B with the oil layer?
(c) Identify the independent variable and the controlled factors in this experiment.

Detailed Analytical Solution & Marking Scheme

(a) Successful Germination & Hypothesis:
Seeds in Cup C will successfully germinate. Aarav's hypothesis was: "Seeds require both moisture (water), oxygen (air), and suitable temperature to break dormancy and germinate."

(b) Purpose of Cup B:
The oil layer forms an impermeable barrier that prevents atmospheric oxygen (air) from dissolving into the water. This cup tests whether water alone is sufficient for germination in the absence of air.

(c) Variables Identified:
• Independent Variable: Environmental growth conditions (Moisture, Air, and Temperature availability).
• Controlled Factors (Constants): Same type and count of gram seeds, same type of container, and identical testing duration.

Chapter 2: Diversity in the Living World

NCERT Curiosity (Class 6) — Plant Diversity, Roots & Venation, Animal Habitats, Adaptations & Biodiversity Conservation | CBSE 2026-27

📌 Key Biological Concepts & Organism Classification

Biodiversity: The vast variety of plants, animals, and microorganisms living across various terrestrial and aquatic ecosystems on Earth.
Plant Classification by Stature:
- Herbs: Small plants with green, soft, and tender stems (e.g., Tomato, Mint, Wheat).
- Shrubs: Medium-sized plants with a hard, woody stem branching out near ground level (e.g., Rose, Lemon).
- Trees: Tall plants with a thick, hard, brown woody trunk branching high above ground (e.g., Mango, Neem, Banyan).
- Creepers & Climbers: Weak-stemmed plants that trail on soil (Pumpkin) or climb up supports using tendrils (Money plant).
Leaf Venation & Root Architecture:
- Reticulate Venation (Net-like): Associated with a Taproot System with a single thick primary root and lateral secondary roots (e.g., Gram, Mustard, Radish, Kidney Bean).
- Parallel Venation (Linear): Associated with a Fibrous Root System with a cluster of slender roots originating from stem base (e.g., Wheat, Grass, Maize, Bamboo).
Animal Classification: Grouping animals by habitat (Aquatic, Terrestrial, Amphibious), reproduction (Oviparous egg-layers vs Viviparous live-bearers), and locomotion methods.

Figure 2.1: Morphological Relationship Between Seeds, Leaves, and Roots

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Here are two types of seeds: Wheat and Kidney bean. What differences do you find among the roots and leaf venation of their plants?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Plant / Seed Type	Type of Seed	Leaf Venation Pattern	Root Architecture
Wheat Plant	Monocotyledon (Monocot): Seed consists of a single cotyledon.	Parallel Venation: Veins run parallel and straight alongside each other from base to leaf tip.	Fibrous Root System: A dense cluster of slender, thread-like roots of nearly equal thickness emerging from the base of the stem.
Kidney Bean Plant (Rajma)	Dicotyledon (Dicot): Seed splits into two distinct cotyledons.	Reticulate Venation: Veins branch out repeatedly, forming a complex net-like or webbed pattern over the lamina.	Taproot System: A single, prominent, thick central main root (taproot) that grows deep downwards with smaller lateral branches.

Biological Principle: Seeds with one cotyledon (monocots) always develop parallel leaf venation and fibrous roots, whereas seeds with two cotyledons (dicots) develop reticulate leaf venation and a taproot system.

CBSE Board Marking Scheme 2026-27

Identification of Monocot vs Dicot nature of Wheat and Kidney Bean1 Mark

Contrasting Leaf Venation (Parallel vs Reticulate) with description1 Mark

Contrasting Root Systems (Fibrous vs Taproot) with description1 Mark

Group the following animals based on their habitats (Aquatic, Terrestrial, or Both): Horse, Dolphin, Frog, Sheep, Crocodile, Squirrel, Whale, Earthworm, Pigeon, and Tortoise.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Classification by Habitat:

Group A — Strictly Aquatic Animals (Live only in water):
- Dolphin: Mammal living exclusively in marine and river water; uses flippers and tail flukes to swim.
- Whale: Large marine mammal spending its entire lifecycle in oceans.
Group B — Strictly Terrestrial Animals (Live on land / aerial):
- Horse: Four-legged terrestrial mammal adapted for grasslands.
- Sheep: Terrestrial herbivore adapted for grazing on land pastures.
- Squirrel: Arboreal terrestrial rodent living in trees.
- Pigeon: Aerial/terrestrial bird living on land habitats and trees.
Group C — Amphibious / Both Land & Water:
- Frog: Amphibian; lays eggs in water, tadpoles swim in water, adults live on land and in ponds (breathes through moist skin and lungs).
- Crocodile: Reptile that swims and hunts in water but rests, sunbathes, and lays eggs on dry land.
- Tortoise: Reptile capable of living on land while some species enter water; freshwater turtles inhabit both land and water.
- Earthworm: Subterranean creature living in moist soil where water and terrestrial nutrients coexist; breathes through moist skin.

CBSE Board Marking Scheme 2026-27

Correctly placing Dolphin and Whale in Aquatic habitat1 Mark

Correctly placing Horse, Sheep, Squirrel, and Pigeon in Terrestrial habitat1 Mark

Correctly placing Frog, Crocodile, Tortoise, and Earthworm in Both/Amphibious1 Mark

Examine a radish plant. Identify its root type and leaf venation. Can you predict the type of root of a plant just by observing its leaves without pulling it out?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Radish Observations:
• Root System: The edible radish is a modified, swollen Taproot (fusiform taproot) that stores food, with fine lateral root hairs emerging from its sides.
• Leaf Venation: The leaves of a radish plant exhibit prominent Reticulate Venation with an intricate net-like web of veins.

2. Prediction Without Digging:
Yes, absolutely. There is a direct, reliable biological correlation in flowering plants:
• If a plant's leaves have Reticulate Venation, it will invariably possess a Taproot System.
• If a plant's leaves have Parallel Venation, it will possess a Fibrous Root System.
Therefore, by simply observing the net-like venation of radish leaves, one can confidently deduce that its root is a taproot without uprooting it.

CBSE Board Marking Scheme 2026-27

Identification of Radish as Taproot and leaves having Reticulate Venation1 Mark

Scientific explanation that leaf venation reliably indicates root architecture1 Mark

Look at a mountain goat and a goat found in the plains. Point out the similarities and differences between them, and explain the biological reasons for these differences.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Similarities:
Both are herbivorous mammals belonging to the goat family. They have four legs, cloven hooves, horns, chew the cud (ruminants), and feed on grasses, leaves, and shrubs.

2. Differences & Habitat Adaptations:

Feature	Mountain Goat	Plains Goat
Body Fur / Coat	Has a thick, double-layered coat of dense, long fur and wool to trap body heat against sub-zero freezing temperatures and biting mountain winds.	Has short, thin hair that allows body heat to radiate away easily in hot and humid plains climates.
Hooves & Agility	Possesses strong, specialized hooves with rubbery, non-skid pads and sharp hard rims for gripping steep, slippery, jagged rocks.	Has standard flat hooves suitable for walking and grazing across level, grassy plains.
Body Build	Stocky, muscular body with a low centre of gravity to maintain balance on rocky precipices.	Leaner, taller body suited for grazing over open fields.

CBSE Board Marking Scheme 2026-27

Stating 2 valid morphological/biological similarities1 Mark

Contrasting body coat (dense fur vs thin hair) and explaining thermal adaptation1 Mark

Contrasting hoof adaptation for rocky slopes vs flat plains1 Mark

Group the following animals based on a feature other than habitat (such as mode of reproduction or presence of wings/movement): Cow, Cockroach, Pigeon, Bat, Tortoise, Whale, Fish, Grasshopper, and Lizard.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Classification Scheme: Mode of Reproduction (Viviparous vs Oviparous):
We can classify these animals into two distinct scientific categories based on how they produce offspring:

1. Viviparous Animals (Give birth to live young and nurse them with milk):
- Cow: Terrestrial mammal giving birth to calves.
- Bat: Flying mammal giving birth to live pups.
- Whale: Aquatic mammal giving birth to live calves in oceans.
2. Oviparous Animals (Egg-laying organisms):
- Cockroach: Insect that lays eggs enclosed in an ootheca.
- Pigeon: Bird that lays hard-shelled eggs in nests.
- Tortoise: Reptile that buries leathery eggs in sandy ground.
- Fish: Aquatic vertebrate laying soft jelly-like eggs in water.
- Grasshopper: Insect laying eggs in soil.
- Lizard: Reptile laying small eggs in wall crevices.

CBSE Board Marking Scheme 2026-27

Clearly defining the chosen classification criterion (Reproduction or Locomotion)1 Mark

Correctly categorising all Viviparous organisms (Cow, Bat, Whale)1 Mark

Correctly categorising all Oviparous organisms (Cockroach, Pigeon, etc.)1 Mark

Discuss how large-scale deforestation affects our surroundings and the living world. Suggest three practical ways to address this environmental challenge.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Adverse Effects of Deforestation:
• Loss of Biodiversity & Wildlife Habitat: Forests provide shelter and nourishment to thousands of species. Cutting trees renders animals homeless, leading to human-animal conflicts and species extinction.
• Soil Erosion & Flash Floods: Tree roots anchor the topsoil firmly. In their absence, torrential rains wash away fertile topsoil, silting rivers and causing floods.
• Climate Change & Global Warming: Trees absorb carbon dioxide during photosynthesis. Fewer trees result in higher atmospheric CO₂ levels, accelerating global warming and altering rainfall patterns.

2. Practical Solutions:
1. Afforestation & Reforestation: Organizing mass tree-plantation drives like Van Mahotsav in school campuses, community parks, and degraded forest lands.
2. Practicing the 3Rs (Reduce, Reuse, Recycle): Recycling paper notebooks and packaging materials to significantly reduce the commercial demand for cutting down pulpwood trees.
3. Strict Enforcement & Protected Biospheres: Enforcing strict anti-poaching laws and preserving sacred groves and national sanctuaries.

CBSE Board Marking Scheme 2026-27

Explaining two major consequences of deforestation on living organisms1.5 Marks

Suggesting three actionable remedial measures (Afforestation, Recycling, Conservation)1.5 Marks

CBSE Competency-Based Question (Ecological Habitat Case Study)

Case Study: Desert vs Aquatic Plant Morphological Adaptations:
During an environmental science field study, students inspected a prickly Opuntia (Cactus) thriving in arid sand and a Lotus plant floating gracefully in a village pond.
(a) How has the Cactus modified its leaves, stem, and root system to survive extreme desert drought?
(b) How are the leaves and stems of a Lotus specially adapted for an aquatic lifestyle?
(c) Why do submerged freshwater plants (like Hydrilla and Vallisneria) possess thin, ribbon-like leaves?

Detailed Analytical Solution & Marking Scheme

(a) Xerophytic Adaptations of Cactus:
• Leaves: Modified into sharp spines to drastically eliminate transpiration water loss and deter grazing herbivores.
• Stem: Green, succulent, and spongy; performs photosynthesis and stores substantial water reserves beneath a thick waxy cuticle.
• Roots: Deep-penetrating taproots that spread horizontally over vast areas near the surface to quickly absorb fleeting rainfall.

(b) Hydrophytic Adaptations of Lotus:
• Leaves: Broad circular leaves coated with a waxy water-repellent layer that prevents rot. Stomata are located solely on the upper sun-exposed surface.
• Stem (Petiole): Long, slender, hollow stalks containing abundant air chambers (aerenchyma) that provide buoyancy and flex with water currents.

(c) Function of Ribbon-like Submerged Leaves:
Narrow, thin ribbon leaves bend easily with flowing water currents without offering mechanical resistance, preventing the plant from tearing or being uprooted.

Chapter 3: Mindful Eating: A Path to a Healthy Body

NCERT Curiosity (Class 6) — Nutrients, Chemical Testing (Starch, Fats, Proteins), Balanced Diet, Traditional Culinary Wisdom & Deficiency Diseases | CBSE 2026-27

📌 Key Nutritional Principles & Food Components

Major Essential Nutrients:
- Carbohydrates: Primary source of instant energy (Starches & Sugars in Rice, Wheat, Potatoes, Maize).
- Fats: Concentrated energy reserves (Butter, Ghee, Mustard oil, Groundnuts, Almonds).
- Proteins: Bodybuilding nutrients essential for tissue growth, cell repair, and enzyme synthesis (Pulses, Gram, Soya bean, Milk, Paneer, Eggs).
- Vitamins & Minerals: Protective nutrients defending against infections, regulating biochemical pathways, maintaining bone, teeth, and vision health.
- Dietary Fibre (Roughage) & Water: Aids digestion, maintains gut microbiome, and prevents constipation.
Millets (Shree Anna / Nutri-Cereals): Jowar (Sorghum), Bajra (Pearl millet), and Ragi (Finger millet) are climate-resilient, mineral-rich superfoods high in calcium, iron, and fibre.
Mindful Eating: Conscious selection of freshly cooked, minimally processed foods that nourish bodily organs over calorie-dense, ultra-processed junk food.

Figure 3.1: Characteristic Color Reactions & Spot Tests for Food Nutrients

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Pick the odd one out and give scientific reasons for your choice:
(i) Jowar, Bajra, Ragi, Chana
(ii) Kidney beans, Green gram, Soya bean, Rice

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) Jowar, Bajra, Ragi, Chana:
• Odd One Out: Chana (Chickpea).
• Scientific Reason: Jowar (Sorghum), Bajra (Pearl millet), and Ragi (Finger millet) are Millets (Nutri-cereals) belonging to the grass family (Poaceae) and are rich sources of carbohydrates, minerals, and dietary roughage. In contrast, Chana is a Pulse (Legume) belonging to the Fabaceae family and is primarily a rich source of plant proteins.

(ii) Kidney beans, Green gram, Soya bean, Rice:
• Odd One Out: Rice.
• Scientific Reason: Kidney beans (Rajma), Green gram (Moong), and Soya bean are all Pulses/Legumes that serve as powerhouse sources of Proteins (bodybuilding nutrients). On the other hand, Rice is a Cereal grain composed predominantly of Carbohydrates (Starch), acting primarily as an energy-giver.

CBSE Board Marking Scheme 2026-27

Identification of Chana with Millets vs Pulse justification1.5 Marks

Identification of Rice with Carbohydrate vs Protein justification1.5 Marks

Discuss traditional versus modern culinary practices in India. How do these changes impact the nutritional value of our food and personal health?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Aspect	Traditional Culinary Practices	Modern Culinary Practices
Cooking Equipment & Fuel	Clay pots, iron kadhais, and brass vessels cooked over earthen chulhas or slow flame. Stone sil-batta used for crushing fresh spices.	Non-stick cookware, pressure cookers, microwaves, and electric high-speed blenders.
Ingredients & Grains	Whole grains, unpolished rice, indigenous millets (Jowar, Bajra, Ragi), cold-pressed unrefined oils, and farm-fresh seasonal vegetables.	Refined flour (maida), polished white rice, refined seed oils, pre-packaged spice mixes, and chemical preservatives.
Nutritional & Health Impact	Slow cooking preserved heat-sensitive vitamins and dietary fibre. Stone grinding enriched minerals without heat damage. Kept gut health strong.	High refining strips off natural fibre and essential B-vitamins. Excessive salt, refined sugars, and trans-fats contribute to lifestyle disorders (obesity, diabetes, constipation).

CBSE Board Marking Scheme 2026-27

Contrasting cooking methods and cookware (chulha/sil-batta vs modern appliances)1.5 Marks

Evaluating nutritional consequences (fibre loss, refined foods, health disorders)1.5 Marks

A science teacher remarks that "Good food may act as medicine." Ravi is curious about this statement and has some questions. List at least two thoughtful questions that Ravi can ask his teacher.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Thoughtful Questions Ravi can ask his science teacher:
1. "How do specific natural foods and Indian kitchen spices (such as turmeric containing curcumin, ginger, garlic, and amla packed with Vitamin C) heal body tissues and enhance immunity against seasonal infections without pharmaceutical medicines?"
2. "Can nutritional deficiencies like iron-deficiency anaemia or Vitamin A night blindness be completely cured simply by including iron-rich green leafy vegetables (spinach) and beta-carotene foods (carrots, papaya) in our daily diet?"
3. "Why are traditional millets like Ragi and Bajra recommended by doctors to manage blood sugar and strengthen bones instead of relying on vitamin pills?"

CBSE Board Marking Scheme 2026-27

Formulating two relevant, scientifically grounded inquiry questions1 Mark each (Total 2 Marks)

"Not all delicious foods are necessarily healthy, while not all nutritious foods are always enjoyable." Share your thoughts on this statement with examples, and explain the importance of mindful eating.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Delicious but Unhealthy Foods:
Ultra-processed foods such as potato chips, deep-fried samosas, burgers, pastries, and carbonated soft drinks are engineered to be extremely delicious due to high concentrations of refined sugar, salt, and trans-fats. However, they lack dietary roughage, vitamins, and minerals. Regular intake leads to lethargy, tooth decay, childhood obesity, and cardiovascular strain.

2. Nutritious but Less Palatable Foods:
Vegetables like bitter gourd (karela), plain boiled lentils, raw sprouted fenugreek, and boiled spinach may possess an unappealing bitter or bland taste for young children. Yet, they are loaded with vital micronutrients: iron, folates, dietary fibre, and antioxidants that cleanse the blood, improve vision, and maintain bowel health.

3. Essence of Mindful Eating:
Mindful eating is the conscious habit of eating food to nourish the body's internal organs rather than merely satisfying momentary tongue cravings. It involves: • Recognizing hunger versus emotional snacking.
• Chewing food slowly to facilitate salivary enzyme action.
• Balancing taste and nutrition by cooking vegetables creatively with traditional spices.

CBSE Board Marking Scheme 2026-27

Discussion of junk vs healthy foods with realistic examples1.5 Marks

Clear articulation of mindful eating principles and balanced dietary mindset1.5 Marks

Describe the step-by-step laboratory procedures to test for: (i) Starch, (ii) Fats, and (iii) Proteins in given food samples. Include required chemical reagents and expected color changes.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) Test for Starch (Carbohydrates):
• Procedure: Take a small portion of the food sample (e.g., a freshly cut slice of raw potato or boiled rice paste). Add 2 to 3 drops of dilute Iodine solution using a dropper.
• Observation: The food surface turns an intense Blue-Black color.
• Inference: Formation of blue-black complex confirms the presence of starch.

(ii) Test for Fats:
• Procedure: Wrap a small piece of food (e.g., crushed groundnut kernel or a drop of mustard oil) in a clean piece of white paper and crush it gently without tearing the paper.
• Observation: An oily, translucent patch appears on the paper.
• Inference: When held against light, the patch lets faint light pass through, proving the presence of fats.

(iii) Test for Proteins (Biuret Test):
• Procedure: Grind a small quantity of food (e.g., boiled egg white or powdered dal paste) and transfer it into a clean test tube with 10 drops of water. Shake thoroughly. Add 2 drops of Copper Sulphate (CuSO₄) solution and 10 drops of Caustic Soda (NaOH) solution. Shake well and leave undisturbed for 5 minutes.
• Observation: The mixture changes to a distinct Violet / Purple color.
• Inference: The violet hue confirms the presence of proteins.

CBSE Board Marking Scheme 2026-27

Starch test with iodine and blue-black observation1 Mark

Fat test with paper translucent spot observation1 Mark

Protein test with CuSO₄ + NaOH and violet observation1 Mark

Complete the clinical deficiency table: Correlate the deficiency disease with its missing nutrient, characteristic physiological symptoms, and preventive dietary sources for: Night blindness, Scurvy, Rickets, Goitre, and Anaemia.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Deficiency Disease	Deficient Nutrient	Key Symptoms	Recommended Dietary Remedies
Night Blindness	Vitamin A	Poor vision in dim light, dry cornea, loss of vision at night.	Carrots, Papaya, Mango, Milk, Green leafy vegetables, Fish liver oil.
Scurvy	Vitamin C	Bleeding, swollen gums; wounds take an abnormally long time to heal.	Citrus fruits (Amla, Orange, Lemon, Guava), Tomatoes.
Rickets	Vitamin D & Calcium	Soft, brittle, and bent bones; bow legs and pigeon chest in children.	Milk, Dairy products, Eggs, exposure of skin to morning sunlight.
Goitre	Iodine	Swollen thyroid gland in neck, mental disability in growing children.	Iodised salt, Seafood, Seaweed.
Anaemia	Iron	Extreme weakness, fatigue, pale skin and nails, shortness of breath.	Spinach, Jaggery (Gur), Apples, Pomegranates, Lentils.

CBSE Board Marking Scheme 2026-27

Accurate matching of missing vitamins/minerals for all 5 diseases1.5 Marks

Accurate identification of symptoms and therapeutic dietary sources1.5 Marks

CBSE Competency-Based Question (Clinical Nutrition Case Study)

Case Study: School Mid-Day Meal & Hidden Hunger:
A health checkup in a rural primary school revealed that several 11-year-old students complained of extreme tiredness, pale nails, bleeding gums during tooth brushing, and difficulty reading the blackboard in dim twilight.
(a) Diagnose the two specific nutritional deficiencies causing (i) bleeding gums, and (ii) twilight vision impairment.
(b) Which mineral deficiency leads to pale fingernails and lethargy? Suggest two affordable local foods to treat it.
(c) Why has the Government of India mandated the inclusion of Millets (Shree Anna) like Ragi and Bajra in Mid-Day Meals?

Detailed Analytical Solution & Marking Scheme

(a) Nutritional Diagnoses:
• (i) Bleeding gums: Caused by Vitamin C deficiency (Scurvy).
• (ii) Twilight vision impairment: Caused by Vitamin A deficiency (Night Blindness).

(b) Mineral Deficiency & Remedy:
• Mineral: Iron deficiency leads to Anaemia (inadequate hemoglobin synthesis).
• Local Dietary Remedies: Locally available Jaggery (Gur) and green leafy vegetables like Spinach (Palak) or Methi, along with roasted chana.

(c) Scientific Rationale for Millets in Mid-Day Meals:
Millets are nutritional powerhouses rich in calcium (Ragi strengthens growing bones), dietary iron (prevents anaemia), and complex carbohydrates with high fibre (promotes sustained mental alertness and healthy bowel movement without sudden sugar spikes).

Chapter 4: Exploring Magnets

NCERT Curiosity (Class 6) — Magnetic Materials, Poles of a Magnet, Laws of Attraction & Repulsion, Magnetic Compass, Earth's Magnetism & Care | CBSE 2026-27

📌 Key Magnetic Principles & Field Concepts

Discovery & Types of Magnets: Natural magnet is Magnetite (iron ore, Fe₃O₄). Artificial magnets come in various shapes: Bar, Horseshoe, Cylindrical, Ring, and Ball-ended magnets.
Magnetic vs Non-Magnetic Materials:
- Magnetic: Materials attracted towards a magnet (Iron, Nickel, Cobalt, Steel).
- Non-Magnetic: Materials experiencing no magnetic force (Wood, Plastic, Paper, Aluminium, Copper, Glass).
Poles of a Magnet: Every magnet has two distinct poles where magnetic attraction is concentrated: North Pole (N) and South Pole (S). Magnetic poles always exist in inseparable pairs. Monopoles do not exist.
Fundamental Law of Magnetism:
- Unlike (opposite) poles ATTRACT: North attracts South (N ↔ S).
- Like (similar) poles REPEL: North repels North (N ⇄ N); South repels South (S ⇄ S). Repulsion is the only sure test of magnetism!
Directive Property & Magnetic Compass: A freely suspended magnet always settles along Earth's geographic North-South direction. This directive property is utilized in the magnetic compass for navigation.

Figure 4.1: Magnetic Field Distribution and Pole Concentration of a Bar Magnet

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Fill in the blanks:
(i) Unlike poles of two magnets ________ each other, whereas like poles ________ each other.
(ii) The materials that are attracted towards a magnet are called ________.
(iii) The needle of a magnetic compass rests along the ________ direction.
(iv) A magnet always has ________ poles.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) Unlike poles of two magnets attract each other, whereas like poles repel each other.
(ii) The materials that are attracted towards a magnet are called magnetic materials.
(iii) The needle of a magnetic compass rests along the north-south direction.
(iv) A magnet always has two poles (North pole and South pole).

CBSE Board Marking Scheme 2026-27

Each correct fill in the blank0.5 Mark each (Total 2 Marks)

State whether the following statements are True (T) or False (F). Correct the false statement(s):
(i) A magnet can be broken into pieces to obtain a single isolated pole.
(ii) Similar poles of two magnets repel each other.
(iii) Iron filings mostly stick in the middle of a bar magnet when brought near it.
(iv) A freely suspended bar magnet always aligns with the north-south direction.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) False. Correction: Magnetic monopoles do not exist. When a magnet is broken in two, each broken piece instantly develops both a North pole and a South pole.
(ii) True. Similar (like) magnetic poles (N-N or S-S) always repel each other.
(iii) False. Correction: Iron filings stick predominantly at the two ends (poles) of a bar magnet, where magnetic force is strongest. Very few filings cling to the middle.
(iv) True. Due to interaction with Earth's magnetic field, a freely suspended magnet always points in the geographic North-South direction.

CBSE Board Marking Scheme 2026-27

Correct True/False evaluation and accurate corrections for false statements0.5 Mark each (Total 2 Marks)

Column I shows different positions in which one pole of a magnet is placed near that of another. Column II indicates the resulting interaction between them for different situations. Complete the table:
• N placed near N
• N placed near S
• S placed near S
• S placed near N

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Column I (Pole Positions)	Column II (Resulting Interaction)	Scientific Law
North pole (N) near North pole (N)	Repulsion (Repel)	Like poles repel
North pole (N) near South pole (S)	Attraction (Attract)	Unlike poles attract
South pole (S) near South pole (S)	Repulsion (Repel)	Like poles repel
South pole (S) near North pole (N)	Attraction (Attract)	Unlike poles attract

CBSE Board Marking Scheme 2026-27

Each correct interaction identified0.5 Mark each (Total 2 Marks)

Atharv performed an experiment in which he took a bar magnet and rolled it over a heap of steel U-clips. What observation is he most likely to make? Explain the scientific reason behind this observation.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Atharv's Observation:
A very large number of steel U-clips cling to both the ends (poles) of the bar magnet, forming thick clusters. Almost no or very few clips stick to the central region (middle) of the bar magnet.

2. Scientific Explanation:
The magnetic attractive force of a bar magnet is not distributed uniformly throughout its length. The magnetic force lines are most concentrated and intense near the two terminal ends, termed the magnetic poles (North and South poles). The magnetic strength weakens rapidly towards the centre of the magnet.

CBSE Board Marking Scheme 2026-27

Observation: clips crowd heavily at ends, negligible at middle1 Mark

Scientific explanation of magnetic force concentration at poles1 Mark

Reshma bought three identical metal bars from the market. Out of these bars, two were magnets and one was just a piece of iron. How will she identify which two amongst the three are magnets, without using any other material?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Principle: Repulsion is the only sure test of magnetism. An unmagnetized iron bar is attracted by both poles of a magnet, but two magnets will repel each other when like poles face each other.

Step-by-Step Identification Procedure:
1. Label the three identical bars as Bar A, Bar B, and Bar C.
2. Take Bar A and bring one of its ends near both ends of Bar B, one by one.
3. Repeat this test by pairing Bar B with Bar C, and Bar A with Bar C.
4. Result Analysis: • Whichever pair of bars shows repulsion at one of their end orientations MUST BOTH BE MAGNETS.
• The remaining third bar, which shows only attraction towards both ends of the other two bars and never exhibits repulsion, is the plain unmagnetized iron bar.

CBSE Board Marking Scheme 2026-27

Stating the core principle that repulsion is the only sure test of magnetism1 Mark

Describing pairwise testing of ends of the three bars1 Mark

Concluding that the pair exhibiting repulsion are magnets, third is iron1 Mark

You are given a magnet which does not have its poles marked. How can you find its poles with the help of another magnet which has its poles clearly marked?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Procedure using Laws of Magnetism:
1. Take the marked magnet and bring its known North pole (N) close to one end (say End 1) of the unmarked magnet.
2. Observe the interaction:
• If End 1 is repelled by the marked North pole, then End 1 is definitely the North pole (since like poles repel). Consequently, the opposite end (End 2) must be the South pole.
• If End 1 is attracted, bring the marked North pole near End 2. If End 2 is repelled, then End 2 is the North pole and End 1 is the South pole.
3. Always confirm using the repulsion test, as repulsion is conclusive.

CBSE Board Marking Scheme 2026-27

Bringing known North pole near ends of unmarked magnet1 Mark

Applying repulsion rule (like poles repel) to identify poles1 Mark

A bar magnet has no markings to indicate its poles. How would you find out near which end its North pole is located without using another magnet?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Method of Free Suspension (Directive Property):
1. Tie a piece of thin thread around the exact middle of the unmarked bar magnet so that it balances horizontally.
2. Suspend the magnet freely from a wooden stand in an area away from iron objects and air currents.
3. Rotate the magnet gently and allow it to come to rest naturally.
4. Repeat this 2 to 3 times to ensure consistency.

Inference:
• A freely suspended magnet always aligns itself along the geographic North-South direction.
• Observe the position of sunrise (East) to identify geographic North.
• The end of the bar magnet that points towards the Geographic North is the North-seeking pole (North Pole) of the magnet.
• The opposite end pointing towards geographic South is the South Pole.

CBSE Board Marking Scheme 2026-27

Description of free suspension setup using thread and stand1 Mark

Stating alignment along geographic North-South direction1 Mark

Identifying end pointing to Geographic North as North Pole1 Mark

If the Earth is itself a giant magnet, can you guess the poles of Earth's magnet by looking at the direction of a magnetic compass? Explain the scientific rationale.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Deduction:
1. The North-seeking pole (North pole) of a magnetic compass needle points towards the Earth's geographic North pole.
2. We know from the fundamental law of magnetism that unlike poles attract.
3. Therefore, for the North pole of the compass needle to be pulled towards geographic North, the Earth must have its magnetic South pole situated near the geographic North Pole.
4. Similarly, Earth's magnetic North pole lies near the geographic South Pole.

CBSE Board Marking Scheme 2026-27

Stating that compass North pole is attracted towards geographic North1 Mark

Deducing that Earth's magnetic South pole lies near geographic North1 Mark

While a mechanic was repairing an electronic gadget using a screwdriver, the tiny steel screws kept falling down into hard-to-reach corners. Suggest a practical solution to solve the mechanic's problem on the basis of what you have learnt in this chapter.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Practical Scientific Solution:
The mechanic can easily magnetize the tip of the steel screwdriver using the single-touch stroke method: 1. Take a strong permanent bar magnet and stroke the metal shaft and tip of the screwdriver from handle to tip 30 to 40 times in the same direction, lifting the magnet after each stroke.
2. Alternatively, simply keep a strong magnet attached to the metal shaft of the screwdriver.
3. The magnetized steel tip will attract and hold the tiny steel screws firmly, preventing them from falling during precision repairs.

CBSE Board Marking Scheme 2026-27

Suggesting magnetizing the screwdriver tip using stroke method or holding a magnet1 Mark

Explaining that magnetized tip attracts and holds steel screws safely1 Mark

Q10

Two ring magnets X and Y are placed on a vertical wooden stand. It is observed that magnet X floats in air and does not move down to touch magnet Y. What could be the possible reason? Suggest a way to bring magnet X into contact with magnet Y, without pushing either magnet.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Reason for Floating:
Magnet X floats above magnet Y because their like poles face each other (either North facing North or South facing South). Since like magnetic poles repel, the upward repulsive force balances the downward gravitational pull on magnet X, causing it to levitate in mid-air without touching Y.

2. Way to Bring Them in Contact (Without Pushing):
Remove ring magnet X from the vertical rod, flip it upside down (invert its faces), and slide it back onto the rod.
Now, the opposite (unlike) poles of magnets X and Y will face each other. Since unlike poles attract, magnet X will naturally be pulled downward by magnetic attraction and sit flush on magnet Y.

CBSE Board Marking Scheme 2026-27

Explaining repulsion between like facing poles causing levitation1.5 Marks

Suggesting inverting/flipping magnet X so unlike poles attract1.5 Marks

Q11

Three bar magnets are placed touching end-to-end on a table in a row: Magnet A (ends 1 and 2), Magnet B (ends 3 and 4), and Magnet C (ends 5 and 6). If they all attract each other and stay together, and end 5 is known to be a North pole (N), deduce the polarity of ends 1, 2, 3, 4, and 6.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Given:
• Three bar magnets touch end-to-end: [1—Magnet A—2] [3—Magnet B—4] [5—Magnet C—6].
• All adjacent touching ends attract each other, which means touching ends are unlike poles.
• End 5 is North (N).

Deduction Step-by-Step:
1. For Magnet C: If end 5 is North (N), the other end of the same magnet, End 6, must be South (S).
2. At the junction between Magnet B and Magnet C: End 4 touches End 5 (N) and attracts it. Therefore, End 4 must be South (S).
3. For Magnet B: If end 4 is South (S), the opposite end of the same magnet, End 3, must be North (N).
4. At the junction between Magnet A and Magnet B: End 2 touches End 3 (N) and attracts it. Therefore, End 2 must be South (S).
5. For Magnet A: If end 2 is South (S), the opposite end, End 1, must be North (N).

Summary of Polarities:
• End 1 = North (N)
• End 2 = South (S)
• End 3 = North (N)
• End 4 = South (S)
• End 5 = North (N) [Given]
• End 6 = South (S)

CBSE Board Marking Scheme 2026-27

Deducing End 6 = South from opposite pole of Magnet C0.5 Mark

Deducing End 4 = South and End 3 = North for Magnet B1 Mark

Deducing End 2 = South and End 1 = North for Magnet A1.5 Marks

Q12

Using 3 to 4 different magnets of various sizes and shapes, try to lift steel pins or U-clips and count how many each magnet picks up. Why do different magnets pick up different numbers of pins?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Observation & Reasoning:
Different magnets attract and lift varying numbers of steel pins because their magnetic strengths are not identical. The magnetic strength of a magnet depends on several scientific factors: 1. Material Composition: Strong neodymium (rare-earth) magnets have much greater magnetic flux density than ordinary ferrite or ceramic magnets.
2. Manufacturing Magnetization: The strength of the external magnetic field applied to magnetize the material during manufacturing.
3. Size and Shape: A larger or thicker magnet of the same material contains more aligned magnetic domains and can lift more pins.
4. Age & Storage Conditions: Magnets that were dropped, heated, or stored without keepers lose partial magnetism over time.

CBSE Board Marking Scheme 2026-27

Stating that magnets possess different magnetic field strengths1 Mark

Listing at least two valid factors (material, size, domain alignment, aging)1 Mark

CBSE Competency-Based Question (Modern Engineering Case Study)

Case Study: Maglev Trains & Demagnetization Hazards:
High-speed Magnetic Levitation (Maglev) trains in countries like Japan and China travel at over 500 km/h without touching railway tracks. Electromagnets on the train undercarriage and the track have identical magnetic poles facing each other.
(a) Which fundamental principle of magnetism allows the Maglev train to float above the track?
(b) What are two major advantages of a floating train over conventional wheeled trains?
(c) Why are laboratory magnets kept with soft iron keepers across their poles when stored for long periods?

Detailed Analytical Solution & Marking Scheme

(a) Working Principle:
Maglev trains operate on the Principle of Magnetic Repulsion (Like poles repel each other). Because similar poles on the track and train face each other, the powerful upward repulsive force lifts the entire weight of the train 10 to 15 mm into the air.

(b) Advantages over Wheeled Trains:
1. Zero Mechanical Friction: Without wheel-rail contact, there is no physical friction, allowing ultra-high speeds with significantly less energy consumption.
2. Whisper-Quiet Operation & Low Maintenance: There is almost no noise pollution or mechanical wear and tear of tracks.

(c) Function of Magnetic Keepers:
When stored freely, isolated magnetic poles demagnetize themselves over time due to interaction with Earth's magnetic field and thermal vibration. Soft iron keepers provide a closed magnetic loop (path for magnetic field lines), preserving magnetic strength indefinitely.

Chapter 5: Measurement of Length and Motion

NCERT Curiosity (Class 6) — SI Standard Units, Metrology, Parallax Error, Measuring Curved Lines, Rest & Motion, Types of Motion | CBSE 2026-27

📌 Key Metrological & Kinematic Principles

Need for Standard Units: Ancient non-standard units (handspan, cubit, foot, pace) varied from person to person. The International System of Units (SI) standardized the metre (m) as the universal base unit of length.
Standard Length Conversions:
- 1 kilometre (km) = 1,000 metres (m)
- 1 metre (m) = 100 centimetres (cm) = 1,000 millimetres (mm)
- 1 centimetre (cm) = 10 millimetres (mm)
Three Essential Rules for Accurate Ruler Measurement:
- Alignment: Place the ruler exactly parallel and touching the length being measured.
- Avoiding Damaged Ends: If the zero mark is broken, start from any clear integer mark (e.g., 2.0 cm) and subtract that from the final reading: True Length = Final Mark - Initial Mark.
- Eliminating Parallax Error: The eye must be placed vertically directly above the scale mark. Looking from an oblique angle gives false readings.
Rest vs Motion: An object is in motion if its position changes relative to a stationary reference point (frame of reference) over time.
Classification of Motion:
- Linear (Rectilinear) Motion: Movement along a straight line (e.g., car moving on a straight road, falling apple).
- Circular Motion: Movement along a circular path maintaining a constant distance from a fixed center (e.g., hands of a clock, blades of ceiling fan).
- Periodic / Oscillatory Motion: Motion that repeats itself at regular fixed intervals of time (e.g., pendulum of a clock, child on a swing, vibrating guitar string).

Figure 5.1: Geometry of Correct Scale Reading & Parallax Avoidance

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Some lengths are given in Column I. Some units are given in Column II. Match the lengths with the most appropriate units for measuring them:
• Distance between Delhi and Lucknow
• Thickness of a coin
• Length of an eraser
• Length of school playground

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Column I (Object / Distance)	Column II (Most Suitable Unit)	Scientific Justification
Distance between Delhi and Lucknow	Kilometre (km)	Large geographical and inter-city distances require the kilometre unit (1 km = 1,000 m).
Thickness of a coin	Millimetre (mm)	Extremely tiny dimensions smaller than 1 cm require the precision of millimetres.
Length of an eraser	Centimetre (cm)	Small handheld stationery items are conveniently measured in centimetres (1 cm = 10 mm).
Length of school playground	Metre (m)	Medium outdoor human-scale distances are best measured using the SI standard unit of metre.

CBSE Board Marking Scheme 2026-27

Each correct matching with scientific reason0.5 Mark each (Total 2 Marks)

Read the following statements and mark True (T) or False (F) against each. Correct the false statement(s):
(i) The motion of a car moving on a straight road is an example of linear motion.
(ii) Any object which is changing its position with respect to a reference point with time is said to be in motion.
(iii) 1 km = 100 cm.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Statement	True / False	Scientific Correction / Explanation
(i) The motion of a car moving on a straight road is an example of linear motion.	TRUE	Motion along a straight-line track is strictly rectilinear (linear) motion.
(ii) Any object which is changing its position with respect to a reference point with time is said to be in motion.	TRUE	This is the fundamental physics definition of relative motion.
(iii) 1 km = 100 cm.	FALSE	Correction: 1 km = 1,000 m = 1,000 × 100 cm = 100,000 cm (1 lakh cm).

CBSE Board Marking Scheme 2026-27

Identifying True/False for parts (i) and (ii)0.5 Mark each

Marking False and providing correct conversion for part (iii)1 Mark

Why cannot a handspan be used as a standard unit of length? Explain with a simple classroom example.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Scientific Reason:
A handspan (the maximum distance between the tip of the thumb and the tip of the little finger when stretched out) varies widely from person to person depending on body size and age. An adult has a much longer handspan than a young child.

2. Classroom Example:
If a teacher and a student both measure the length of the same classroom blackboard using their handspans:
• The teacher's handspan may measure 10 handspans.
• The student's smaller handspan may measure 14 handspans.
Because the value is not constant and cannot be universally reproduced, a handspan cannot serve as a standard scientific unit. Standard units like the metre (m) have fixed, constant lengths worldwide.

CBSE Board Marking Scheme 2026-27

Explanation of variation in body dimensions1 Mark

Classroom example illustrating discrepancy1 Mark

Take two measuring scales from your geometry box. Compare their smallest markings (divisions). What is the least count of each scale? Why is least count important in measurement?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Definition of Least Count:
The smallest value of a physical quantity that can be measured directly and accurately using a measuring instrument is called its least count.

2. Comparison of Standard 15-cm School Rulers:
• On a standard school plastic ruler, each 1 centimetre is subdivided into 10 equal divisions.
• Therefore, the value of 1 smallest division = 1 cm ÷ 10 = 0.1 cm = 1 mm.
• The least count of a standard school ruler is 1 mm (0.1 cm).

3. Importance of Least Count:
Least count determines the maximum precision and resolution of an instrument. An object whose dimension is smaller than 1 mm cannot be accurately measured with a standard ruler without error.

CBSE Board Marking Scheme 2026-27

Correct calculation of least count (1 mm or 0.1 cm)1 Mark

Significance in precision and measurement limits1 Mark

The distance between Radhika's home and her school is 1.5 km. Express this distance in:
(i) metres (m)
(ii) centimetres (cm)

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Given: Distance = 1.5 km

(i) Conversion into Metres (m):
We know that 1 km = 1,000 m.
Therefore: Distance = 1.5 × 1,000 m = 1,500 m.

(ii) Conversion into Centimetres (cm):
We know that 1 m = 100 cm.
Therefore: Distance = 1,500 × 100 cm = 150,000 cm (1.5 × 10⁵ cm).

CBSE Board Marking Scheme 2026-27

Step-by-step conversion into metres (1,500 m)1 Mark

Step-by-step conversion into centimetres (150,000 cm)1 Mark

Explain with the help of a neat labelled diagram how you would measure the perimeter of the circular bottom of a drinking glass tumbler using a piece of thread and a metre scale.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Figure 5.2: Method of Measuring Curved Perimeter with Thread and Ruler

Method & Procedure:
A straight rigid ruler cannot bend around the circular boundary of a glass tumbler. Therefore, we use an inelastic piece of cotton thread:

Tie a small knot or put an ink mark 'A' near one end of the thread.
Place mark 'A' on any point along the rim of the tumbler base.
Wrap the thread snugly all the way around the circular circumference without stretching or overlapping.
Put a second ink mark 'B' where the thread meets mark 'A' to complete exactly one full turn.
Unwind and stretch the thread straight along a standard metre scale, placing mark 'A' at 0 cm.
The reading at mark 'B' directly gives the perimeter (circumference) of the tumbler base.

CBSE Board Marking Scheme 2026-27

Step-by-step description of thread wrapping & marking1.5 Marks

Transferring to straight ruler & reading procedure1 Mark

Neat labelled diagram0.5 Mark

The height of a person is 1.65 m. Express this height into centimetres (cm) and millimetres (mm).

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Given: Height = 1.65 m

1. Conversion into Centimetres (cm):
Since 1 m = 100 cm:
Height = 1.65 × 100 cm = 165 cm.

2. Conversion into Millimetres (mm):
Since 1 cm = 10 mm (or 1 m = 1,000 mm):
Height = 165 × 10 mm = 1,650 mm (or 1.65 × 1,000 mm = 1,650 mm).

CBSE Board Marking Scheme 2026-27

Height in centimetres (165 cm) with working1 Mark

Height in millimetres (1,650 mm) with working1 Mark

A student wants to measure the thickness of a single 5-rupee coin using an ordinary 15-cm school ruler. How can this be done accurately? Explain with calculation steps.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Figure 5.3: Method of Magnification via Multi-Coin Stacking

1. Experimental Problem:
A single coin is only about 1.5 to 2 mm thick. Because the smallest division on a standard school ruler is 1 mm, measuring a single coin directly carries high relative error.

2. Method of Multi-Coin Stacking:
• Take 10 identical 5-rupee coins and stack them closely on top of each other without gaps.
• Place the ruler vertically along the stack and measure the total height H of the 10 coins (suppose H = 18 mm).
• Calculate the thickness of a single coin by dividing total height by 10:
Thickness of 1 Coin = Total Stack Height (H) ÷ Number of Coins (n) = 18 mm ÷ 10 = 1.8 mm (0.18 cm).

CBSE Board Marking Scheme 2026-27

Concept of stacking multiple coins to minimize least-count error1 Mark

Formula and division step1 Mark

Differentiate between Rectilinear motion, Circular motion, and Periodic motion. Give two real-life examples for each type.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Type of Motion	Scientific Definition	Two Real-Life Examples
Rectilinear (Linear) Motion	Motion in which an object moves along a straight line path with all parts travelling in the same direction.	1. A car moving on a straight highway. 2. An apple falling straight down from a tree.
Circular Motion	Motion in which an object moves along a circular path such that its distance from a fixed central point remains constant.	1. The tip of the second hand of a watch. 2. A point marked on the blade of a rotating ceiling fan.
Periodic Motion	Motion that repeats itself at regular, equal intervals of time.	1. The swinging of a clock pendulum. 2. A child swinging back and forth on a swing.

CBSE Board Marking Scheme 2026-27

Rectilinear motion definition & 2 examples1 Mark

Circular motion definition & 2 examples1 Mark

Periodic motion definition & 2 examples1 Mark

Q10

Observe different everyday objects around you. It is easier and more convenient to express the dimensions of some objects in mm, some in cm, and some in m. Make a list of three objects in each category with scientific reasons.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Measurement Unit	Objects Best Expressed in this Unit	Scientific Convenience Reason
Millimetres (mm)	1. Thickness of a 10-rupee coin 2. Diameter of a ballpoint pen tip (0.5 mm or 0.7 mm) 3. Length of a tiny grain of rice	These dimensions are extremely small (sub-centimetre); using cm would result in inconvenient decimal fractions.
Centimetres (cm)	1. Length of a pencil 2. Width of a science textbook 3. Length of a toothbrush	Handheld personal items have lengths between 5 cm and 30 cm, making the centimetre scale easy to read and visualize.
Metres (m)	1. Length of a classroom blackboard 2. Height of a room door 3. Length of a curtain or saree	Larger everyday dimensions exceed 100 cm; expressing them in metres avoids unwieldy large three- or four-digit numbers.

CBSE Board Marking Scheme 2026-27

Three appropriate objects listed for millimetres (mm) with reason1 Mark

Three appropriate objects listed for centimetres (cm) with reason1 Mark

Three appropriate objects listed for metres (m) with reason1 Mark

CBSE Competency-Based Question (Experimental Measurement Case Study)

Case Study: Measuring with a Broken Zero Mark:
Sneha wanted to measure the length of her knitting needle using a 15-cm plastic ruler. However, the zero mark of the ruler was chipped and broken off. She placed the needle starting at the 2.0 cm mark and observed the other end at 14.3 cm.
(a) What is the true length of Sneha's knitting needle?
(b) What common error would occur if Sneha viewed the ruler mark from a side angle rather than vertically above?
(c) A tailor uses a flexible tape to measure chest size rather than a wooden metre ruler. Why?

Detailed Analytical Solution & Marking Scheme

(a) True Length Calculation:
When the zero mark is broken, subtract the initial reading from the final reading:
True Length = Final mark - Initial mark = 14.3 cm - 2.0 cm = 12.3 cm (or 123 mm).

(b) Name of Error:
Viewing from an oblique angle causes Parallax Error, leading to an inaccurate reading. The eye must be positioned perpendicularly directly above the measurement mark.

(c) Reason for Flexible Tape:
The human body has curved surfaces. A rigid wooden ruler cannot bend around curves, whereas a flexible measuring tape bends smoothly along bodily contours to measure circumferences accurately.

Chapter 6: Materials Around Us

NCERT Curiosity (Class 6) — Properties of Materials, Lustre, Hardness, Solubility, Transparency & Waste Segregation | CBSE 2026-27

📌 Key Material Properties & Classification Principles

Definition of Matter: Anything that occupies space (volume) and possesses mass is called matter.
Physical Properties for Sorting Materials:
- Lustre (Shine): Freshly cut surfaces of metals (Gold, Silver, Copper, Aluminium) shine brightly. Non-metals (wood, rubber, chalk) are dull.
- Hardness vs Softness: Hard materials cannot be scratched or compressed easily (Iron, Diamond). Soft materials can be compressed or scratched easily (Sponge, Wax, Cotton).
- Solubility in Water: Substances that dissolve completely and disappear in water are soluble (Sugar, Salt). Those that do not mix are insoluble (Sand, Chalk powder, Mustard oil).
- Density (Floating vs Sinking): Objects less dense than water float (Dry leaves, Wood, Oil). Denser objects sink (Iron nail, Stone).
Optical Transparency:
- Transparent: Materials through which light passes freely, allowing objects to be seen clearly (Clean glass, Air, Pure water).
- Translucent: Materials allowing partial light to pass through, so objects are seen hazily/blurred (Oiled paper, Butter paper, Frosted glass).
- Opaque: Materials blocking all light; cannot see through at all (Wood, Cardboard, Metals).

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Visit your kitchen and observe how your parents have organized various edibles. Can you suggest a better sorting method? Write it down in your notebook with scientific justification.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Kitchen Observation:
In most kitchens, food items are typically arranged based on daily frequency of use and physical shelf size rather than scientific categories.

2. Proposed Systematic Scientific Sorting Method:
Edibles should be segregated into distinct labelled zones based on material properties and storage requirements: • Zone 1 — Whole Grains & Flours (Dry Staples): Wheat flour (Atta), Rice, Millets stored in large, airtight stainless steel bins to keep out moisture and insects.
• Zone 2 — Pulses & Legumes (Dals): Moong, Chana, Rajma, Toor dal kept in transparent glass or clear plastic jars arranged alphabetically for instant visual identification.
• Zone 3 — Spices & Seasonings: Turmeric, Cumin, Mustard seeds, Salt kept in a moisture-free multi-compartment spice box (masala dabba) near the cooking stove.
• Zone 4 — Liquid Edibles: Mustard oil, Ghee, Vinegar kept in non-reactive bottles on lower spill-proof trays.
• Zone 5 — Perishable Produce: Fresh vegetables and fruits stored in ventilated wicker baskets or refrigerator crispers.

CBSE Board Marking Scheme 2026-27

Recording realistic kitchen observation0.5 Mark

Proposing systematic categorization based on material states and properties1.5 Marks

Unscramble the letters in Column I and match them with their characteristic properties given in Column II:
• T R E M A T
• U L S B E L O
• T N E R P A S N A R T
• E R U S T L

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Jumbled Letters (Column I)	Unscrambled Scientific Term	Matching Property (Column II)
T R E M A T	MATTER	Occupies space and possesses mass
U L S B E L O	SOLUBLE	Dissolves / mixes completely in water
T N E R P A S N A R T	TRANSPARENT	Objects can be seen through it clearly
E R U S T L	LUSTRE	Shiny appearance on freshly exposed surface

CBSE Board Marking Scheme 2026-27

Each correct unscrambling and property matching0.5 Mark each (Total 2 Marks)

The containers used to store materials in shops and at home are usually transparent (such as glass jars or clear plastic containers). Give scientific and practical reasons for this practice.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Reasons for Using Transparent Containers:
1. Optical Property of Transparency: Transparent materials allow light to pass through unobstructed. This enables shopkeepers and homemakers to see the stored items inside clearly from outside without opening the lid.
2. Time Efficiency & Convenience: Customers in a grocery shop can locate pulses, candies, or spices instantly, saving time and preventing frequent opening that exposes food to air moisture and pests.
3. Monitoring Stock & Quality: It allows quick visual inspection of remaining quantities and early detection of spoilage, fungal growth, or insect infestation.

CBSE Board Marking Scheme 2026-27

Explaining property of transparency allowing clear light transmission1 Mark

Stating practical benefits (instant visual identification, stock monitoring)1 Mark

State whether the statements given below are True (T) or False (F). Correct the false statement(s):
(i) Wood is translucent while glass is opaque.
(ii) Aluminium foil has lustre while an eraser does not.
(iii) Sugar dissolves in water whereas sawdust does not.
(iv) An apple is matter because it occupies no space and has mass.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) False. Correction: Wood is opaque (blocks all light) while clean glass is transparent (allows light to pass through completely).
(ii) True. Aluminium is a metal and possesses metallic lustre (shine), whereas an eraser is made of rubber and has a dull, non-lustrous surface.
(iii) True. Sugar crystals are soluble and dissolve completely between water molecules, whereas sawdust particles are insoluble and float/remain suspended.
(iv) False. Correction: An apple is matter because it occupies definite space (volume) AND has mass.

CBSE Board Marking Scheme 2026-27

Each correct evaluation and rectification0.5 Mark each (Total 2 Marks)

We see chairs made up of various materials such as wood, iron, plastic, bamboo, cement, and stones. Which of these materials fulfil the following desirable properties the most?
(i) Hardness (does not bend or shake on sitting even after long use)
(ii) Lightweight (easy to lift or take from one place to another)
(iii) Does not feel very cold when sitting during winters
(iv) Can be cleaned regularly and made to look new even after long use

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Material Matching:
• (i) High Hardness & Rigidity: Iron, Stone, or Cement fulfill this property the most because of their high tensile strength and rigid crystalline structures; they do not bend or deform under heavy load.
• (ii) Lightweight & Portability: Plastic or Bamboo fulfill this best because they have low density, making them lightweight and very easy to carry.
• (iii) Thermal Comfort in Winter (Poor Conductor of Heat): Wood or Bamboo fulfill this property best because they are thermal insulators. Unlike metals or stone, they do not conduct heat rapidly away from the human body, so they do not feel icy cold to sit on.
• (iv) Ease of Regular Cleaning & Washing: Plastic or Polished Stainless Steel/Iron fulfill this best because they are non-porous, waterproof, resistant to stains, and can be washed with soapy water without rotting.

CBSE Board Marking Scheme 2026-27

Each correct material choice matched with scientific property rationale0.75 Mark each (Total 3 Marks)

You need to have containers for the collection of: (i) Food waste, (ii) Broken glass pieces, and (iii) Wastepaper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Waste Category	Chosen Container Material	Essential Material Properties Considered
(i) Food Waste (Wet Kitchen Waste)	High-density Plastic (with a tight-fitting lid)	Waterproof, non-corrosive, non-porous, and easily washable: Food waste is moist and decays, releasing liquids and foul odours. Plastic will not rust, leak, or rot, and can be washed daily.
(ii) Broken Glass Pieces (Sharp Hazard)	Thick Heavy-duty Metal / Galvanized Iron or thick rigid plastic bucket	High puncture resistance, hardness, and mechanical toughness: Sharp jagged glass edges can easily pierce paper or thin bags, injuring sanitation workers. Strong metal walls prevent punctures.
(iii) Wastepaper (Dry Recyclable)	Cardboard box, wicker basket, or light plastic bin	Lightweight, dry, and breathable: Wastepaper is light and dry. A simple lightweight container keeps the papers neatly stacked without taking up unnecessary weight.

CBSE Board Marking Scheme 2026-27

Choice of container and properties for food waste (plastic, waterproof)1 Mark

Choice of container and properties for broken glass (metal, puncture-resistant)1 Mark

Choice of container and properties for wastepaper (cardboard/light bin)1 Mark

Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in front of us, we cannot see through it. Why is it so? Explain using optical properties of materials.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Optical Explanation:
• Air is a Transparent Medium: Clean air consists of widely spaced gas molecules that allow light rays to travel straight through without reflecting or absorbing them. Because light reflected from objects reaches our eyes unimpeded, air does not hinder visibility.
• Wood is an Opaque Material: A wooden door is dense and solid. Its molecules absorb or reflect all incident light rays completely, allowing zero light to pass through. Since no light from objects behind the door can reach our eyes, we cannot see through a wooden door.

CBSE Board Marking Scheme 2026-27

Explaining that air is transparent and transmits light completely1 Mark

Explaining that wood is opaque and blocks light transmission1 Mark

A substance X is hard, rigid, cannot be compressed easily, and dissolves completely in water. Another substance Y is soft, highly compressible, and does not dissolve in water. Identify substances X and Y from daily life and justify your answer.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Identification & Justification:
• Substance X: Common Rock Salt (or Sugar crystal / Alum).
Justification: Salt or sugar crystals have a rigid crystalline lattice that makes them hard and virtually incompressible under finger pressure, yet their polar chemical bonds allow them to dissolve completely in water.
• Substance Y: Sponge (or Cotton wool / Foam).
Justification: A sponge has tiny pores filled with air, allowing it to be easily compressed when squeezed. It is made of insoluble synthetic polyurethane or cellulose fibres that do not dissolve in water.

CBSE Board Marking Scheme 2026-27

Identifying Substance X (Rock salt / Sugar) with property justification1 Mark

Identifying Substance Y (Sponge / Cotton) with property justification1 Mark

Solve the "Who Am I?" material riddles:
(i) I shine brightly when freshly cut and conduct heat well.
(ii) I can be easily compressed because I have many air cavities inside me.
(iii) I am hard, but when dropped in water, I vanish completely.
(iv) You can see light through me, but you cannot see objects clearly.
(v) I have mass and occupy volume, but you cannot touch or hold me in your hands.

[2.5 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) A Metal (e.g., Copper, Aluminium, Iron, Silver): Possesses metallic lustre and thermal conductivity.
(ii) A Sponge (or Foam): High compressibility due to trapped air in microscopic pores.
(iii) Common Salt / Sugar: Hard crystalline solids exhibiting high water solubility.
(iv) A Translucent Object (e.g., Butter paper, Frosted glass, Oiled paper): Transmits partial diffuse light.
(v) Air (or Atmospheric Gas): Invisible matter having mass and volume.

CBSE Board Marking Scheme 2026-27

Each correct identification0.5 Mark each (Total 2.5 Marks)

Q10

You are provided with the following materials: Vinegar, Honey, Mustard oil, Water, Glucose, and Wheat flour.
(a) Make any two pairs of materials where one material is soluble/miscible in the other.
(b) Make two pairs of materials where one material remains insoluble/immiscible in the other.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(a) Soluble / Miscible Pairs (Dissolve completely forming a uniform mixture):
1. Glucose in Water: Solid glucose powder dissolves completely in water to form a clear sweet solution.
2. Vinegar in Water (or Honey in Water): Vinegar is an aqueous solution of acetic acid that mixes completely (miscible) with water.

(b) Insoluble / Immiscible Pairs (Do not dissolve; remain separate):
1. Mustard Oil and Water: Mustard oil is non-polar and less dense than water; it forms a separate floating layer on top of water (immiscible liquids).
2. Wheat Flour and Water: Wheat flour contains insoluble starches and gluten; it forms a cloudy suspension that settles at the bottom over time.

CBSE Board Marking Scheme 2026-27

Two correct soluble pairs with scientific justification1 Mark

Two correct insoluble pairs with scientific justification1 Mark

CBSE Competency-Based Question (Industrial Material Selection Case Study)

Case Study: Cooking Utensil Design & Thermal Properties:
An industrial product designer is manufacturing a modern kitchen frying pan. The pan consists of two distinct components: a metal base and a handle.
(a) Why is the body of the frying pan made of stainless steel or aluminium rather than wood or plastic?
(b) Why is the handle made of Bakelite (hard plastic) or wood rather than copper?
(c) Explain why cooking oil floats on water when cleaning oily utensils in a sink.

Detailed Analytical Solution & Marking Scheme

(a) Body Material Rationale:
Aluminium and stainless steel are excellent conductors of heat and have high melting points. They conduct heat rapidly and evenly to cook food without burning or warping.

(b) Handle Material Rationale:
Wood and Bakelite plastic are thermal insulators (poor conductors of heat). Even when the pan base becomes scorching hot on the stove, the handle remains cool, allowing safe handling without burning one's hands.

(c) Flotation of Cooking Oil:
Cooking oil has a lower density than water and is immiscible in water. Because its buoyant force exceeds its downward weight per unit volume, it forms a distinct layer floating above water.

Chapter 7: Temperature and its Measurement

NCERT Curiosity (Class 6) — Clinical vs Laboratory Thermometers, Kink Function, Least Count, Reading Temperature & Digital Thermometers | CBSE 2026-27

📌 Key Thermometric Principles & Measurement Standards

Definition of Temperature: A reliable quantitative measure of the degree of hotness or coldness of an object. The standard SI unit is Kelvin (K); commonly measured in degree Celsius (°C) and degree Fahrenheit (°F).
Normal Human Body Temperature: 37.0 °C (equivalent to 98.6 °F).
Clinical Thermometer:
- Used specifically to measure human body temperature.
- Range: 35 °C to 42 °C (or 94 °F to 108 °F).
- Features a narrow constriction (kink) just above the bulb that prevents the mercury level from dropping immediately when taken out of the mouth or armpit.
Laboratory Thermometer:
- Used to measure temperatures in scientific experiments.
- Range: Typically -10 °C to 110 °C.
- Has NO kink; must be read while the bulb is still immersed in the liquid.
Least Count of a Thermometer: The value of the smallest subdivision on the graduated capillary stem.

Figure 7.1: Architectural Distinction: Presence of Kink in Clinical Thermometer

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

The normal temperature of a healthy human being is close to:
(i) 98.6 °C
(ii) 37.0 °C
(iii) 32.0 °C
(iv) 27.0 °C

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (ii) 37.0 °C
Scientific Explanation: The average physiological body temperature of a healthy human being is 37.0 °C on the Celsius scale. (Option (i) is 98.6 °F in Fahrenheit, but not 98.6 °C, which would be fatal boiling heat!).

CBSE Board Marking Scheme 2026-27

Selecting option (ii) 37.0 °C1 Mark

37 °C is the same temperature as:
(i) 97.4 °F
(ii) 97.6 °F
(iii) 98.4 °F
(iv) 98.6 °F

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (iv) 98.6 °F
Temperature Conversion:
Formula: F = (C × 9/5) + 32
F = (37 × 1.8) + 32 = 66.6 + 32 = 98.6 °F.

CBSE Board Marking Scheme 2026-27

Selecting option (iv) 98.6 °F with temperature scale relationship1 Mark

Fill in the blanks:
(i) The hotness or coldness of a system is determined by its ________.
(ii) The temperature of ice-cold water cannot be measured by a ________ thermometer.
(iii) The standard unit of temperature is degree ________ or degree ________.

[1.5 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) The hotness or coldness of a system is determined by its temperature.
(ii) The temperature of ice-cold water cannot be measured by a clinical thermometer (because its scale only begins at 35 °C, while ice-cold water is near 0 °C).
(iii) The standard unit of temperature is degree Celsius (°C) or degree Fahrenheit (°F) (SI unit: Kelvin).

CBSE Board Marking Scheme 2026-27

Each correct fill in the blank0.5 Mark each (Total 1.5 Marks)

What is the usual temperature range of a laboratory thermometer? Why does it have a much wider range than a clinical thermometer?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Standard Range:
The range of a standard laboratory thermometer is usually -10 °C to 110 °C.

2. Reason for Wider Range:
A laboratory thermometer is designed for general scientific experiments involving ice-water mixtures (freezing point near 0 °C), boiling water (boiling point 100 °C), and various chemical reactions. In contrast, a clinical thermometer is designed exclusively to measure human body temperature, which fluctuates only within a narrow survival window of 35 °C to 42 °C.

CBSE Board Marking Scheme 2026-27

Stating range -10 °C to 110 °C1 Mark

Explaining scientific experiments require freezing and boiling points1 Mark

Four students used a laboratory thermometer to measure the temperature of water in a beaker:
• Student A tilted the thermometer at 45°.
• Student B immersed the thermometer bulb so that it touched the bottom of the beaker.
• Student C immersed the thermometer so that the bulb touched the side wall of the beaker.
• Student D held the thermometer vertically upright with the bulb fully immersed in water without touching the walls or bottom.
Who followed the correct procedure? Explain the necessary precautions.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Correct Procedure: Student D.

Scientific Precautions for Laboratory Thermometers:
1. Keep it Vertically Upright: Tilting the thermometer (Student A) causes distorted meniscus views and inaccurate gravitational settling of the mercury thread.
2. Do Not Touch the Container Surfaces: Touching the bottom (Student B) or side walls (Student C) records the direct temperature of the heated glass beaker rather than the liquid water.
3. Complete Immersion: The bulb containing thermometric liquid must be completely surrounded by the substance being measured.
4. Read While Immersed: Since laboratory thermometers lack a kink, the reading must be taken while the bulb remains immersed.

CBSE Board Marking Scheme 2026-27

Identifying Student D as correct1 Mark

Explaining why touching sides/bottom or tilting gives erroneous readings2 Marks

Explain how you read the temperature on a thermometer scale. If the level of liquid column stands three small divisions above 35 °C on a scale where each small division represents 0.2 °C, what is the exact temperature reading?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Step-by-Step Calculation:
• Main scale reading = 35.0 °C
• Number of subdivisions above main mark = 3 divisions
• Value of 1 small division (least count) = 0.2 °C
• Additional temperature = 3 × 0.2 °C = 0.6 °C
• Total Temperature Reading = 35.0 °C + 0.6 °C = 35.6 °C.

CBSE Board Marking Scheme 2026-27

Showing calculation (3 × 0.2 = 0.6 °C)1 Mark

Final correct temperature reading of 35.6 °C1 Mark

Observe a thermometer where the markings between 20 °C and 30 °C have 10 equal divisions.
(a) What is the value of each division (least count)?
(b) If the liquid column reaches the 7th division above 20 °C, what is the temperature?
(c) What type of thermometer is likely to have this range?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

(a) Value of Each Division (Least Count):
Difference between major markings = 30 °C - 20 °C = 10 °C.
Number of divisions = 10.
Value of 1 division = 10 °C ÷ 10 = 1.0 °C.

(b) Temperature Reading:
Reading = Base value + (7 × 1.0 °C) = 20 °C + 7 °C = 27.0 °C.

(c) Type of Thermometer:
This is a Laboratory Thermometer (or Room / Weather Thermometer), because a clinical thermometer only measures between 35 °C and 42 °C with divisions of 0.1 °C or 0.2 °C.

CBSE Board Marking Scheme 2026-27

Least count calculation (1.0 °C)1 Mark

Temperature reading calculation (27.0 °C)1 Mark

Identification of Laboratory/Room thermometer1 Mark

A laboratory thermometer cannot be used to measure human body temperature. Give two clear scientific reasons.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Reasons:
1. Absence of Kink (Constriction): A laboratory thermometer does not have a kink above its bulb. The moment it is taken out of a patient's mouth or armpit into cooler room air, the mercury column immediately drops down rapidly, giving a false, lower reading before it can be read.
2. Low Precision & Safety Risk: Laboratory thermometers typically have a least count of 1 °C, making them incapable of detecting slight 0.2 °F/0.1 °C fever fluctuations. Furthermore, their long glass stem and toxic mercury pose a breakage hazard inside a patient's mouth.

CBSE Board Marking Scheme 2026-27

Absence of constriction causing immediate mercury drop outside body1 Mark

Low resolution / lack of fever precision and safety hazard1 Mark

Vaishnavi was unwell with a fever. Her mother recorded her body temperature every 4 hours:
• 6:00 AM: 38.5 °C
• 10:00 AM: 39.5 °C
• 2:00 PM: 40.0 °C
• 6:00 PM: 38.0 °C
• 10:00 PM: 37.0 °C
(a) What was Vaishnavi's highest recorded temperature?
(b) At what time was the fever at its peak?
(c) When did her temperature return to normal?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Data Analysis:
• (a) Highest Recorded Temperature: 40.0 °C (high fever).
• (b) Peak Time: The temperature reached its highest value at 2:00 PM.
• (c) Normalization Time: Normal human body temperature is 37.0 °C. Vaishnavi's temperature reached 37.0 °C at 10:00 PM, indicating her recovery from fever.

CBSE Board Marking Scheme 2026-27

Correctly identifying peak temperature (40.0 °C)1 Mark

Correctly identifying peak time (2:00 PM)1 Mark

Identifying return to 37.0 °C at 10:00 PM1 Mark

Q10

If you need to measure a temperature of 22.5 °C accurately, which thermometer would you select: one with smallest divisions of 1 °C, one with 0.5 °C, or one with 2 °C? Explain your choice scientifically.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Choice: The thermometer with smallest divisions of 0.5 °C.
Scientific Reason:
• To measure 22.5 °C without guessing or interpolation, the instrument's least count must be capable of resolving 0.5 °C increments.
• A thermometer with 1 °C divisions only marks 22 °C and 23 °C; reading 22.5 °C would be an eyeball estimation.
• A thermometer with 2 °C divisions only marks 22 °C and 24 °C.
• The 0.5 °C thermometer will have an exact marked graduation for 22.5 °C (one tick mark above 22.0 °C), providing direct and accurate measurement.

CBSE Board Marking Scheme 2026-27

Selection of 0.5 °C division thermometer1 Mark

Explanation that least count must resolve decimal increments directly1 Mark

Q11

A student observes a laboratory thermometer where the mercury thread stands exactly halfway between 27 °C and 28 °C. If there are two equal divisions between 27 °C and 28 °C, what is the exact reading?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Step-by-Step Calculation:
1. Total temperature difference between adjacent degree marks = 28 °C - 27 °C = 1 °C.
2. Number of equal subdivisions = 2.
3. Value of each subdivision = 1 °C ÷ 2 = 0.5 °C.
4. The mercury thread is on the first subdivision above 27 °C.
5. Exact temperature reading = 27 °C + 0.5 °C = 27.5 °C.

CBSE Board Marking Scheme 2026-27

Subdivision least count derivation (0.5 °C)1 Mark

Final reading of 27.5 °C1 Mark

Q12

A laboratory thermometer has 50 equal divisions between 0 °C and 100 °C. What does each division of this thermometer measure (least count)?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Calculation:
• Total temperature span = 100 °C - 0 °C = 100 °C.
• Total number of divisions = 50.
• Value of 1 division = Total temperature span ÷ Total divisions
• Value of 1 division = 100 °C ÷ 50 = 2 °C per division.
Therefore, each single division on this thermometer measures 2 °C.

CBSE Board Marking Scheme 2026-27

Stating formula (Span ÷ Number of divisions)1 Mark

Correct calculation yielding 2 °C per division1 Mark

Q13

Explain how you would design and draw a thermometer scale between 10 °C and 20 °C such that its smallest division reads 0.5 °C. How many total subdivisions must be marked between 10 °C and 20 °C?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Scale Design Calculation:
1. Total temperature difference = 20 °C - 10 °C = 10 °C.
2. Desired least count (value of smallest division) = 0.5 °C.
3. Total number of subdivisions required = Total difference ÷ Least count
Number of divisions = 10 °C ÷ 0.5 °C = 20 subdivisions.

Drawing Steps:
• Draw a straight vertical line and mark the bottom end as 10 °C and top end as 20 °C.
• Mark 10 major degree increments (11 °C, 12 °C, ..., 19 °C).
• Subdivide each 1 °C interval into 2 equal parts with a shorter middle tick mark representing 0.5 °C.
• There will be exactly 20 equal intervals across the whole 10 °C span.

CBSE Board Marking Scheme 2026-27

Calculating total number of divisions (10 ÷ 0.5 = 20 divisions)1 Mark

Describing division layout with 0.5 °C intermediate ticks1 Mark

CBSE Competency-Based Question (Clinical Instrumentation Case Study)

Case Study: Transition from Mercury to Digital Thermometers:
In recent years, hospitals and schools have replaced traditional mercury clinical thermometers with electronic digital thermometers and infrared forehead scanners.
(a) Why is mercury being phased out from household thermometers?
(b) What safety hazard occurs if a mercury thermometer breaks on the floor?
(c) State two practical advantages of digital thermometers over traditional mercury thermometers.

Detailed Analytical Solution & Marking Scheme

(a) Reason for Phasing Out Mercury:
Mercury is a highly toxic, bioaccumulative heavy metal. It vaporizes at room temperature into invisible toxic fumes that damage the central nervous system, lungs, and kidneys.

(b) Breakage Safety Hazard:
When glass breaks, liquid mercury scatters into hundreds of microscopic rolling droplets. It is virtually impossible to clean with a broom or vacuum cleaner without contaminating indoor air and sewage.

(c) Advantages of Digital Thermometers:
1. Mercury-Free & Unbreakable: Uses electronic thermistor sensors housed in durable plastic; completely safe for children.
2. Instant Numerical Display with Beep: Shows direct LCD numerical readings without parallax error, and beeps when reading stabilizes.

Chapter 8: A Journey through States of Water

NCERT Curiosity (Class 6) — Evaporation, Condensation, Transpiration, Water Cycle & Water Conservation | CBSE 2026-27

📌 Key Hydrological Principles & Phase Changes

Three Physical States of Water:
- Solid (Ice/Snow): Rigid form with definite shape and volume; found in glaciers and polar ice sheets.
- Liquid (Water): Fluid form with definite volume but taking container shape; oceans, rivers, groundwater.
- Gas (Water Vapour / Steam): Invisible gaseous state expanding to fill space; present continuously in the atmosphere.
Phase Transformation Processes:
- Evaporation: Conversion of liquid water into water vapour below boiling point; absorbs latent heat, creating a cooling effect. Accelerated by high temperature, large surface area, wind, and low humidity.
- Condensation: Transformation of water vapour into tiny liquid droplets upon cooling; responsible for cloud, dew, and fog formation.
- Transpiration: Biological loss of water vapour through microscopic leaf stomata into the atmosphere.
The Water Cycle: The continuous cyclical circulation of water between Earth's surface and the atmosphere driven by solar radiation.

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Which of the following best describes condensation?
(i) The conversion of water into its vapour state
(ii) The process of water changing from a liquid into a gaseous state
(iii) The formation of clouds from tiny water droplets
(iv) The conversion of water vapour into its liquid state

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (iv) The conversion of water vapour into its liquid state
Scientific Explanation: Condensation is defined specifically as the physical phase transition where water in its gaseous vapour state cools down and condenses back into liquid water droplets.

CBSE Board Marking Scheme 2026-27

Selecting option (iv) with scientific phase definition1 Mark

Identify in which of the given processes evaporation is very important:
(i) Colouring with: (a) crayons, (b) water colours, (c) acrylic colours, (d) pencil colour
(ii) Writing on paper with: (a) pencil, (b) ink pen, (c) ballpoint pen

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) Colouring medium where evaporation is critical:
Correct Option: (b) Water colours
Reason: Water colours are applied by diluting pigment in liquid water. The painting dries and binds to paper only when the water solvent evaporates into the surrounding air. Wax crayons and pencil colours are dry solids that do not involve evaporation.

(ii) Writing tool where evaporation is critical:
Correct Option: (b) Ink pen (Fountain pen)
Reason: Liquid fountain pen ink contains a high proportion of aqueous solvent. For the wet writing to dry on paper without smudging, the liquid water/solvent must evaporate. Pencils use solid graphite, and ballpoint pens use a thick oil-based paste that does not dry primarily by water evaporation.

CBSE Board Marking Scheme 2026-27

Correct option (b) water colours with solvent evaporation reason1 Mark

Correct option (b) ink pen with drying mechanism reason1 Mark

We see green-coloured plastic artificial grass at many places these days. The space around natural living grass feels cooler than the space around plastic grass. Explain why scientifically.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Transpiration & Evaporative Cooling in Natural Grass:
Natural grass is a living plant that continuously absorbs water from the soil through its roots. It releases excess water into the surrounding air as invisible water vapour through microscopic pores (stomata) on its leaves. This biological process is called transpiration.
When liquid water evaporates/transpires from the leaves, it absorbs heat energy (latent heat of vaporization) from the surrounding air. This loss of thermal energy produces a significant natural cooling effect.

2. Heat Retention by Plastic Grass:
Artificial plastic grass is an inanimate petroleum-based synthetic polymer. It does not perform transpiration or evaporation. Instead, plastic absorbs solar radiation, heats up intensely, and radiates heat back into the surrounding air, making the vicinity feel hot and uncomfortable.

CBSE Board Marking Scheme 2026-27

Explaining transpiration in living grass causing evaporative cooling1.5 Marks

Explaining plastic grass lacks transpiration and absorbs/radiates heat1.5 Marks

Give examples of four liquids other than water that evaporate into the air at room temperature. What common property do they share?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Examples of Evaporating Liquids:
1. Ethyl Alcohol (found in Hand Sanitizers): Evaporates rapidly from hands, leaving a cooling sensation.
2. Acetone (Nail Polish Remover): Evaporates almost instantly when left open in a bottle.
3. Perfume / Cologne: Contains volatile alcohol-based fragrance molecules that evaporate into vapor.
4. Petrol (Gasoline): Highly volatile hydrocarbon fuel that evaporates swiftly on contact with air.

Common Scientific Property:
All these substances are volatile liquids possessing relatively weak intermolecular attractive forces, allowing their surface molecules to easily gain kinetic energy and escape into the vapour phase at room temperature.

CBSE Board Marking Scheme 2026-27

Listing 4 valid evaporating liquids (sanitizer, perfume, petrol, acetone)1 Mark

Identifying property of volatility / low boiling point1 Mark

Electric fans blow air around, creating a cooling sensation. It might seem strange to turn on a fan to dry wet clothes, since fans usually make things cooler, not warmer. Normally, evaporation requires heat. Explain scientifically why a fan speeds up the drying of clothes.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Principle: Effect of Wind Speed on Evaporation:
1. Removal of Saturated Boundary Layer: When wet clothes hang in stagnant air, water evaporates and quickly forms a localized, highly humid layer of air immediately surrounding the fabric. High humidity slows down further evaporation.
2. Continuous Air Circulation: When a ceiling fan is switched on, moving air swiftly blows away this humid boundary layer and replaces it with drier room air.
3. Increased Rate of Evaporation: The continuous influx of drier air allows water molecules to escape from the wet cloth fibers much more rapidly.
4. Heat Source: The water molecules absorb the necessary latent heat of vaporization from the room air and the clothes themselves. Hence, high wind speed dramatically accelerates evaporation even without raising the temperature.

CBSE Board Marking Scheme 2026-27

Explaining that fan sweeps away humid air layer surrounding wet clothes1.5 Marks

Explaining replacement with drier air increases rate of evaporation1.5 Marks

Usually, when wet sludge is dredged from municipal drains, it is left in heaps next to the drain for 3 to 4 days before being transported to fields or gardens as manure. What scientific changes occur during these 3-4 days?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Transformations During 3–4 Days of Heap Drying:
1. Evaporation of Water (Dehydration): The water present in wet sludge evaporates under sun and breeze, causing the heavy, runny sludge to dry out into semi-solid clumps. This drastically reduces weight and transportation cost.
2. Solar Disinfection: Exposure to solar ultraviolet (UV) radiation and atmospheric oxygen kills harmful anaerobic pathogens, foul-smelling bacteria, and parasite eggs.
3. Transformation into Safe Manure: Once dehydrated and aerated, the organic sludge becomes odourless, easy to handle, and safe to enrich garden soil with nitrogen and phosphorus.

CBSE Board Marking Scheme 2026-27

Evaporation of excess water reducing weight and handling difficulty1 Mark

Sun exposure killing pathogens and neutralizing foul odour1 Mark

Observe activities in your house for a day. Identify at least four daily household activities that involve evaporation. How does understanding the process of evaporation help us perform these activities more efficiently?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Daily Household Activities Involving Evaporation:
• Drying Wet Clothes: Spreading wet laundry outdoors under the sun.
• Mopping Floors: Washing tiled floors with a damp mop; the thin water film evaporates into room air within minutes.
• Drying Sweaty Skin: Perspiration evaporates from skin under a fan, cooling the body.
• Cooling Drinking Water in an Earthen Pitcher (Matka): Water seeps through porous clay pores and evaporates, cooling the stored water.

2. Practical Benefits of Understanding Evaporation:
• Spreading out Laundry (Surface Area): Knowing that evaporation increases with surface area, we spread clothes wide instead of leaving them bunched up.
• Ventilation: We open windows and switch on fans while mopping floors to dry them faster and prevent slipping accidents.
• Storage Precaution: We seal bottles of medicines, sanitizers, and perfumes tightly to prevent loss through evaporation.

CBSE Board Marking Scheme 2026-27

Listing 4 valid domestic activities involving evaporation1.5 Marks

Applying principles (surface area, airflow, temperature) for efficiency1.5 Marks

How is water present in the solid state in nature? Name three geographical locations where solid water is permanently found on Earth.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Natural Occurrence of Solid Water:
In nature, water exists in the solid state as ice, frost, hail, and snow. It forms naturally wherever environmental temperatures drop below water's freezing point (0 °C).

Key Geographical Locations:
1. Polar Ice Caps (Antarctica and the Arctic): Massive continental ice sheets storing nearly 70% of Earth's fresh water.
2. High Mountain Glaciers (The Himalayas, Alps, Andes): Perennial frozen rivers of compacted snow such as the Gangotri Glacier.
3. High-Altitude Alpine Peaks: Snow-capped mountain summits permanently frozen throughout the year.

CBSE Board Marking Scheme 2026-27

Stating forms of solid water (ice, snow, glaciers)1 Mark

Naming 3 geographic locations (Antarctica, Arctic, Himalayas/Glaciers)1 Mark

Reflect on the environmental statement: "Water is our responsibility before it is our right." Share your thoughts on this statement with two actionable conservation practices.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Ethical & Scientific Reflection:
• Over 97% of Earth's water is saline ocean water unfit for consumption. Out of the remaining 3% freshwater, more than two-thirds is trapped in polar glaciers. Only less than 1% is readily available as surface water in rivers, lakes, and groundwater.
• While clean drinking water is a fundamental human right for survival, claiming this right without exercising responsibility leads to reckless over-extraction, aquifer depletion, and toxic pollution.
• Therefore, conserving and protecting water ecosystems must come first as our primary duty, ensuring equitable availability for future generations and wildlife.

2. Actionable Conservation Practices:
1. Rooftop Rainwater Harvesting: Capturing monsoon rainwater from roofs and channeling it into percolation recharge pits to replenish depleted groundwater tables.
2. Eliminating Wastage at Home: Fixing dripping taps promptly, using a bucket instead of running hoses to wash cars, and reusing kitchen RO wastewater for watering plants.

CBSE Board Marking Scheme 2026-27

Discussion of scarcity of usable fresh water and ethical stewardship1.5 Marks

Two actionable conservation practices (Rainwater harvesting, waste prevention)1.5 Marks

Q10

The seat of a two-wheeler parked outside on a sunny afternoon has become scorching hot. How can you quickly cool it down using what you have learnt about evaporation?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Practical Cooling Solution:
1. Sprinkle a Little Water or Place a Damp Cloth: Sprinkle a few splashes of water onto the hot leatherette/vinyl seat, or cover it with a wet handkerchief/cloth.
2. Scientific Mechanism: Because the dark seat surface is very hot, the applied water film absorbs its latent heat of vaporization directly from the seat material and rapidly evaporates into the surrounding air.
3. Immediate Cooling Effect: The rapid transfer of heat from the seat to evaporating water molecules cools the seat down to ambient temperature within seconds, making it safe and comfortable to sit on.

CBSE Board Marking Scheme 2026-27

Application of water/wet cloth onto hot seat1 Mark

Explaining that evaporating water absorbs heat from seat, cooling it rapidly1 Mark

CBSE Competency-Based Question (Hydrological Cycle Case Study)

Case Study: Cloud Formation & Groundwater Depletion:
During summer, riverbeds dry up while atmospheric humidity and towering thunderclouds increase. Later, heavy rainfall replenishes rivers, but city borewells still run dry.
(a) Why do droplets of water appear on the outer surface of a glass tumbler containing ice-cold water?
(b) Explain why urban cities face severe groundwater depletion despite receiving heavy monsoon rainfall.
(c) What natural process purifies ocean water into fresh rainwater during the water cycle?

Detailed Analytical Solution & Marking Scheme

(a) Condensation on Tumbler Surface:
Air contains invisible water vapour. When warm air collides with the cold outer surface of the ice tumbler, it cools down rapidly below its dew point. The vapour loses heat and condenses into visible liquid water droplets.

(b) Reason for Urban Groundwater Depletion:
Urbanization covers vast land areas with concrete buildings, asphalt roads, and tiled pavements. This creates an impermeable barrier that prevents rainwater from seeping (percolating) into the soil. Most rainfall rushes into stormwater drains and is lost, preventing aquifer recharge.

(c) Natural Purification via Water Cycle:
Solar Evaporation and Distillation: When ocean water evaporates under solar energy, only pure water molecules transform into vapour, leaving salts and impurities behind in the ocean. The condensed rainwater is pure freshwater.

Chapter 9: Methods of Separation in Everyday Life

NCERT Curiosity (Class 6) — Handpicking, Threshing, Winnowing, Sieving, Sedimentation, Decantation, Filtration, Churning & Evaporation | CBSE 2026-27

📌 Key Separation Principles & Techniques

Purpose of Separation: To remove harmful or undesirable impurities, separate useful components from mixtures, or isolate pure substances for analysis.
Separation of Solid-Solid Mixtures:
- Handpicking: Manually sorting visibly different substances based on size, colour, or shape when impurities are in small quantities.
- Threshing: Beating harvested stalks against a hard surface to separate grain seeds.
- Winnowing: Separating heavier components (grains) from lighter components (husk) using blowing wind.
- Sieving: Separating particles of different sizes through wire mesh pores.
Separation of Insoluble Solid-Liquid Mixtures:
- Sedimentation: Allowing heavier insoluble solid particles to settle down at the bottom of a container.
- Decantation: Gently pouring out the upper clear liquid layer without disturbing the settled sediment.
- Filtration: Passing a mixture through a porous filter medium (filter paper, muslin cloth) to completely retain insoluble residue.
Separation of Soluble Solid-Liquid Mixtures:
- Evaporation: Heating a solution until the liquid solvent evaporates away, leaving the solid solute crystals behind (e.g., obtaining salt from seawater).
- Churning (Centrifugation): Rapid spinning of curd/milk to separate lighter cream/butter from heavier liquid whey.

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

What purpose does handpicking serve in the process of separation?
(i) Filtration
(ii) Sorting
(iii) Evaporation
(iv) Decantation

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (ii) Sorting
Scientific Reason: Handpicking is a manual physical method used to selectively sort and remove unwanted impurities (such as pebbles, dirt, or insects) from grains based on visible differences in color, shape, and size.

CBSE Board Marking Scheme 2026-27

Selecting option (ii) Sorting with justification1 Mark

Which of the following substances are commonly separated using the churning method?
(i) Oil from water
(ii) Sand from water
(iii) Cream from milk
(iv) Oxygen from air

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (iii) Cream from milk (or Butter from curd)
Scientific Reason: Churning involves rapid mechanical rotation of the liquid mixture. The lighter fat globules (cream/butter) have lower density and aggregate together, floating to the surface, while the denser liquid buttermilk remains below.

CBSE Board Marking Scheme 2026-27

Selecting option (iii) with density and churning rationale1 Mark

Which factor is usually essential for successful filtration?
(i) Apparatus size
(ii) Presence of air
(iii) Pore size of the filter medium
(iv) Temperature of the mixture

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (iii) Pore size of the filter medium
Scientific Reason: In filtration, separation depends directly on the relative size of insoluble particles compared to the pore dimensions of the filter. Liquid molecules pass through the microscopic pores while larger insoluble solid particles are retained as residue.

CBSE Board Marking Scheme 2026-27

Selecting option (iii) with pore-particle size relationship1 Mark

State with reasons whether the following statements are True (T) or False (F). Correct the false statement(s):
(i) Salt can be separated from a salt solution by keeping it under the Sun.
(ii) Handpicking should be used only when the quantity of the component to be separated is small.
(iii) A mixture of puffed rice and rice grains can be separated by threshing.
(iv) A mixture of mustard oil and lemon water can be separated by decantation.
(v) Sieving is used to separate a mixture of rice flour and water.

[2.5 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) True. Solar heat causes water to evaporate into vapour, leaving solid salt crystals behind as residue (natural method of obtaining sea salt in salt pans).
(ii) True. Handpicking is labor-intensive and practical only when impurities are visibly distinct and present in relatively small amounts.
(iii) False. Correction: Threshing is used to separate grains from dried crop stalks. Puffed rice and rice grains differ significantly in weight and can be separated easily by winnowing (blowing wind carries away lighter puffed rice) or handpicking.
(iv) True. Mustard oil and lemon water are immiscible liquids. Mustard oil floats as a distinct upper layer due to lower density and can be poured off by decantation.
(v) False. Correction: Sieving separates dry solids of different particle sizes. To separate rice flour from water, filtration or sedimentation followed by decantation is used.

CBSE Board Marking Scheme 2026-27

Each correct evaluation and scientific justification0.5 Mark each (Total 2.5 Marks)

Match the mixtures in Column I with their appropriate method of separation in Column II:
• Sand and water
• Common salt dissolved in water
• Iron pins mixed with sulfur powder
• Butter from curd
• Tiny stones from wheat grains

[2.5 Marks]

✅ CBSE Standard Step-by-Step Solution

Mixture (Column I)	Separation Method (Column II)	Underlying Scientific Difference
Sand and water	Sedimentation & Decantation (or Filtration)	Sand is insoluble and heavier than water; settles at bottom.
Common salt dissolved in water	Evaporation	Water evaporates away at boiling/ambient temperatures, leaving salt.
Iron pins mixed with sulfur powder	Magnetic Separation	Iron is magnetic and attracted to a magnet; sulfur is non-magnetic.
Butter from curd	Churning (Centrifugation)	Butter fat has lower density than liquid whey.
Tiny stones from wheat grains	Handpicking	Stones differ visibly in colour and texture from wheat grains.

CBSE Board Marking Scheme 2026-27

Each correct matching with scientific difference identified0.5 Mark each (Total 2.5 Marks)

In what situations would you prefer to use decantation instead of filtration to separate solids from liquids? State two advantages and two limitations of decantation.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

When Decantation is Preferred Over Filtration:
Decantation is chosen when the solid particles are coarse, heavy, and settle rapidly at the bottom of the container (e.g., washing rice or pulses with water before cooking, or separating coarse gravel from muddy water).

Advantages of Decantation:
1. Fast and Convenient: Requires no special filter paper, funnels, or laboratory equipment.
2. No Filter Clogging: Heavy coarse solids would instantly clog and tear delicate filter paper; decantation bypasses this issue easily.

Limitations of Decantation:
1. Incomplete Separation: Extremely fine, suspended clay particles remain floating in the liquid, resulting in turbid water.
2. Loss of Liquid: A small portion of liquid is inevitably left behind to prevent sediment from pouring out.

CBSE Board Marking Scheme 2026-27

Identifying suitable conditions (heavy, fast-settling solids)1 Mark

Stating two valid advantages1 Mark

Stating two valid limitations1 Mark

Can you relate the presence of fine hair inside our nasal cavity to any physical separation process studied in this chapter? Explain the biological mechanism.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Physical Separation Process: Filtration.
Biological Mechanism:
• The fine hair (cilia) and sticky mucus lining inside human nostrils act together as a biological sieve / filter medium.
• When we breathe in air containing suspended dust, smoke particles, pollen grains, and microbes, the air passes through the nasal passages while the larger solid particulate impurities get trapped in the sticky mesh of nasal hair.
• This prevents harmful pollutants from entering our sensitive lungs, functioning exactly like a filter paper retaining solid residue while allowing clean fluid through.

CBSE Board Marking Scheme 2026-27

Correlating nasal hair with Filtration1 Mark

Explaining trapping of dust/pollen as biological filter residue1 Mark

During the COVID-19 pandemic, all of us wore protective face masks. What material are these masks generally made of? What is the scientific role of these masks based on separation principles?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Materials of Masks:
Protective surgical and N95 face masks are typically made of multiple layers of non-woven polypropylene fabric (melt-blown polymer fibres) or closely woven multiple layers of cotton cloth.

2. Scientific Role as a Filter Medium:
• The mask functions on the principle of Filtration.
• The microscopic pores of the melt-blown layer are small enough to allow oxygen and carbon dioxide molecules to pass through freely for breathing, while physically blocking and trapping respiratory droplets, airborne aerosol particles, and virus-laden droplets expelled during coughing, sneezing, or talking.

CBSE Board Marking Scheme 2026-27

Stating material (non-woven polypropylene / multilayer cotton)1 Mark

Explaining filtration of respiratory droplets while allowing gases through1 Mark

A dry mixture containing potatoes, salt, and sawdust has been given to you. Outline a sequential, step-by-step procedure to separate each component from this mixture into pure states.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Stepwise Separation Flow:
1. Step 1: Handpicking (Separating Potatoes):
Potatoes are much larger than salt crystals and sawdust particles. They can be picked out manually by hand, leaving a mixture of salt and sawdust.

2. Step 2: Dissolution in Water:
Add sufficient water to the remaining mixture of salt and sawdust and stir thoroughly with a glass rod. The common salt dissolves completely in water, while the sawdust is insoluble, has a low density, and floats on the water surface.

3. Step 3: Filtration (Separating Sawdust):
Pass the mixture through a filter paper supported in a funnel. The insoluble sawdust is collected as the residue on the filter paper. Wash it with a little water and allow it to dry in the sun.

4. Step 4: Evaporation (Recovering Pure Salt):
Transfer the clear saltwater filtrate into an evaporating dish and heat it gently over a burner. The water evaporates as steam, leaving dry solid common salt crystals behind.

CBSE Board Marking Scheme 2026-27

Step 1: Handpicking of potatoes0.75 Mark

Step 2: Dissolution of salt in water0.75 Mark

Step 3: Filtration to isolate sawdust residue0.75 Mark

Step 4: Evaporation of filtrate to obtain salt0.75 Mark

Q10

Read the story: "Leela and her father were working in their agricultural field on a hot afternoon. They realized they had forgotten to bring drinking water from home. Leela walked to a nearby pond where the water was muddy and turbid. She filled a pot, kept it undisturbed for an hour, strained the upper clear water through her clean cotton dupatta, boiled the water vigorously over a small firewood flame, and cooled it for drinking."
(a) Identify all the scientific separation and purification techniques used by Leela in sequence.
(b) Why was boiling essential before drinking?
(c) Provide a suitable title of your choice for this story.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

(a) Sequential Scientific Techniques Used:
1. Sedimentation: Keeping the muddy water undisturbed for an hour allowed heavier clay and silt particles to settle to the bottom.
2. Decantation & Filtration: Pouring the upper liquid through a cotton dupatta strained out coarse suspended plant debris and remaining fine sediment.
3. Thermal Disinfection (Boiling): Heating the water killed invisible disease-causing bacteria, protozoa, and waterborne pathogens.
4. Cooling: Bringing the sterile potable water back to room temperature for safe hydration.

(b) Necessity of Boiling:
Filtration through cloth only removes visible physical suspended impurities; it cannot remove microscopic living germs and pathogens. Boiling at 100 °C sterilizes the water, preventing waterborne diseases like cholera, typhoid, and dysentery.

(c) Suitable Story Title:
"Intelligent Leela: Science in Action for Safe Drinking Water" (or "Turning Pond Water into Pure Nectar").

CBSE Board Marking Scheme 2026-27

Identification of Sedimentation, Filtration, and Boiling1.5 Marks

Reason for boiling (killing invisible microbial pathogens)1 Mark

Creative, appropriate title0.5 Mark

CBSE Competency-Based Question (Municipal Water Treatment Case Study)

Case Study: Municipal River Water Purification:
A municipal water treatment plant draws raw water from a river and supplies safe potable drinking water to over 50,000 homes in a city.
(a) Alum (phitkari) is added to river water during the loading process. What is the scientific purpose of loading?
(b) Describe the three layers used in municipal sand filters to purify water.
(c) Why is liquid chlorine gas or bleaching powder mixed into the clarified water as the final step before pumping to homes?

Detailed Analytical Solution & Marking Scheme

(a) Purpose of Loading with Alum:
River water contains extremely light, colloidal clay particles that remain suspended indefinitely. Dissolved alum particles attach to these tiny clay particles, making them heavier so that they settle rapidly at the bottom of sedimentation tanks.

(b) Layers in a Sand Filter:
A municipal gravity filter consists of: (1) A fine sand layer at the top to trap microscopic sediment, (2) A coarse sand layer in the middle, and (3) A gravel / pebble bed at the bottom that supports the sand while allowing clear water to drain through.

(c) Chlorination Purpose:
Chlorination is the chemical disinfection stage. Chlorine acts as a powerful germicide that kills all residual bacteria, viruses, and pathogens, ensuring water remains sterile during pipeline transit.

Chapter 10: Living Creatures: Exploring their Characteristics

NCERT Curiosity (Class 6) — Hallmarks of Life, Life Cycles, Metamorphosis, Seed Germination, Stimuli & Plant Tropisms | CBSE 2026-27

📌 Key Biological Principles & Life Processes

Hallmarks of Living Organisms: Cellular structure, Nutrition, Respiration, Growth, Excretion, Reproduction, Response to Stimuli, and a finite Lifespan ending in death.
Life Cycles: Every living creature undergoes sequential developmental changes from origin to maturity and reproduction:
- Plants: Seed → Germination (Radicle & Plumule) → Seedling → Mature Plant → Flower & Fruit → Seed.
- Animals with Metamorphosis: Significant structural transformations between juvenile and adult stages (e.g., Frog: Egg → Aquatic Tadpole with tail & gills → Four-legged Froglet → Terrestrial Adult Frog with lungs; Mosquito: Egg → Aquatic Larva → Pupa → Winged Adult).
Conditions for Seed Germination: Moisture (water), warmth (suitable temperature), and air (oxygen). Light is not strictly required for initial germination under soil.
Plant Responses to Stimuli:
- Geotropism: Roots always grow downwards towards gravity (+ve geotropism), while shoots grow upwards away from gravity (-ve geotropism), regardless of how the seed is planted.
- Phototropism: Plant shoots bend towards light sources to maximize photosynthetic light capture.

Figure 10.1: Complete Metamorphic Life Cycle of a Frog

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

List the similarities and differences in the life cycles of plants and animals.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Feature / Aspect	Similarities	Differences (Plants vs Animals)
Beginning of Life	Both begin life from a single unit containing genetic material.	• Plants: Begin from a seed or spore. • Animals: Begin from an egg or direct birth (viviparous embryo).
Growth & Development	Both grow irreversibly in size and complexity with time.	• Plants: Indeterminate growth throughout life at meristems; produce new roots/branches continuously. • Animals: Determinate growth; stop growing upon reaching adult maturity.
Metamorphosis / Stage Change	Both pass through distinct developmental phases.	• Plants: Pass through germination, seedling, vegetative growth, flowering, and fruiting. • Animals: Many undergo dramatic bodily metamorphosis (e.g., tadpole to frog, caterpillar to butterfly).
Reproduction & Death	Both reproduce to continue their species and eventually experience natural death.	• Plants: Reproduce via flowers, seeds, vegetative parts (cuttings, tubers). • Animals: Reproduce sexually or asexually through specialized reproductive organs.

CBSE Board Marking Scheme 2026-27

Key similarities listed (Growth, reproduction, life cycle progression)1.5 Marks

Key differences listed (Beginning, growth pattern, mode of reproduction)1.5 Marks

The table given below shows some data. Study the data and try to find out examples appropriate for the conditions given in the second and third columns. If you think that an example for any of the conditions given below is not possible, explain why?
• Condition A: Does not move from place to place, but is living.
• Condition B: Moves from place to place, but is non-living.
• Condition C: Grows in size, but is non-living.
• Condition D: Does not grow, does not respire, does not reproduce, but is living.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Condition	Appropriate Example	Scientific Explanation
Condition A: Does not move from place to place, but is living.	Plants and Trees (e.g., Mango tree, Rose plant)	Plants are rooted in soil and do not show locomotion, yet they perform all vital life functions (photosynthesis, respiration, internal growth, response to light).
Condition B: Moves from place to place, but is non-living.	Motor Car / Train / Cloud	Cars move on roads and clouds move across the sky due to external fuel energy or wind forces, but they lack cells, cannot reproduce, and do not respire.
Condition C: Grows in size, but is non-living.	Crystal growth (Alum) / Sand dune	A sand dune grows by external accumulation of wind-blown sand particles, and an alum crystal grows by deposition from solution; this is not internal biological cellular growth.
Condition D: Does not grow, does not respire, does not reproduce, but is living.	NOT POSSIBLE	An entity that lacks growth, respiration, and reproduction cannot be classified as living. These life processes are essential defining hallmarks of organismic life.

CBSE Board Marking Scheme 2026-27

Correct identification of example for Condition A & B1 Mark

Correct identification and explanation for Condition C1 Mark

Reasoned explanation why Condition D is scientifically impossible1 Mark

You have learnt that different conditions are required for seed germination. How can we use this knowledge for the proper storage of grains and pulses?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Conditions Necessary for Germination:
Seeds require moisture (water), oxygen (air), and warmth (suitable temperature) to break dormancy and germinate.

2. Application to Safe Grain Storage:
To prevent grains and pulses from germinating (sprouting) or getting spoiled by fungi and pests during storage, we must intentionally deprive them of these germination conditions:

Sun Drying: Grains are thoroughly dried in the sun to eliminate moisture content below 10-12%. Without water, seeds remain dormant and fungal mold cannot grow.
Airtight and Moisture-Proof Containers: Stored in sealed metal bins or dry silos to keep out atmospheric humidity and dampness.
Cool Storage: Kept in cool, well-ventilated granaries away from high heat.

CBSE Board Marking Scheme 2026-27

Linking germination conditions (water, warmth, air) to dormancy1 Mark

Practical storage methods (sun drying, airtight bins, moisture prevention)1 Mark

You have learnt that a tail is present in a tadpole, but it disappears as it grows into a frog. What is the advantage of having a tail in the tadpole stage? Why is it lost in the adult frog?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Advantage of a Tail in the Tadpole Stage:
A tadpole is an exclusively aquatic organism with no limbs. Its long, finned muscular tail provides essential propulsion for swimming through water, escaping predators, and foraging for aquatic vegetation.

2. Reason for Loss of Tail in the Adult Frog:
During metamorphosis, the frog develops powerful, muscular hind limbs designed for leaping on land and webbed feet for swimming. The tail is reabsorbed by the body tissues to recycle nutrients. On land, a long aquatic tail would be an unnecessary hindrance to hopping and locomotion.

CBSE Board Marking Scheme 2026-27

Advantage of tail for aquatic propulsion in tadpole stage1 Mark

Reason for tail reabsorption (development of hopping limbs for terrestrial life)1 Mark

Charan says that a wooden log is non-living as it cannot move. Charu counters it by saying that it is living because it is made of wood obtained from trees. Give your arguments in favour or against the two statements given by Charan and Charu.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Evaluation of Charan's Statement:
• Conclusion: Charan is partially correct in his conclusion, but his reasoning is scientifically flawed.
• Scientific Argument: A wooden log is indeed non-living, but lack of locomotion is NOT the reason. Many living organisms, such as trees and corals, do not move from place to place yet are living. The log is non-living because its cells are dead, it does not respire, does not take nutrients, and cannot reproduce.

2. Evaluation of Charu's Statement:
• Conclusion: Charu is scientifically incorrect.
• Scientific Argument: While wood was once part of a living tree, once severed from the tree and dried, the cells die. Something that originated from a living organism is not automatically living if it has permanently ceased all metabolic life processes (just as a fallen dry leaf or a bird's feather is non-living).

3. Final Verdict:
A wooden log is classified as non-living (dead organic matter).

CBSE Board Marking Scheme 2026-27

Analysis of Charan's argument (correct conclusion, incomplete reason)1 Mark

Analysis of Charu's argument (distinguishing living origin from current living status)1 Mark

Correct biological conclusion based on metabolic life processes1 Mark

What are the similarities and distinguishing features in the life cycles of a mosquito and a frog?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Aspect	Mosquito Life Cycle	Frog Life Cycle
Similarities	• Both lay eggs in water (aquatic early development). • Both undergo complete metamorphosis with distinct juvenile forms. • The early stage looks entirely different from the adult form. • Both require water bodies for species reproduction.
Stages of Development	4 distinct stages: Egg → Larva (wriggler) → Pupa (tumbler) → Adult	3 primary stages: Egg → Tadpole (with tail & gills) → Adult Frog
Taxonomic Group	Insect (Invertebrate arthropod with 6 legs and wings)	Amphibian (Vertebrate animal with 4 legs and backbone)
Respiration in Adult	Breathes via spiracles and tracheal tubes	Breathes via lungs and moist skin
Adult Habitat & Locomotion	Terrestrial and aerial (flies using wings)	Amphibious (hops on land, swims in water using webbed legs)

CBSE Board Marking Scheme 2026-27

Key similarities listed (aquatic egg laying, metamorphosis)1.5 Marks

Key distinguishing features listed (stages, breathing organs, taxonomy)1.5 Marks

A potted plant is placed horizontally on its side and provided with all the conditions suitable for its growth (light, moisture, warmth). Draw what you expect to see in the shoot and the root of the plant after one week. Write down the scientific reasons.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Figure 10.2: Directional Growth Responses (Tropisms) in Horizontally Placed Plant

Observations After One Week:
• Stem / Shoot: The shoot curves and grows upward towards sunlight (away from gravity).
• Root: The root curves and grows downward into the soil (towards gravity).

Scientific Reasons:
1. Negative Geotropism & Positive Phototropism of Shoot: Shoots are programmed to grow upward against gravity (-ve geotropism) and towards light (+ve phototropism) so leaves can capture sunlight for photosynthesis.
2. Positive Geotropism of Root: Roots are programmed to grow towards gravity (+ve geotropism) into the ground to anchor the plant and absorb water and mineral salts from the soil.

CBSE Board Marking Scheme 2026-27

Accurate diagram showing upward shoot and downward root1 Mark

Scientific reason for shoot growth (Phototropism / Negative geotropism)1 Mark

Scientific reason for root growth (Positive geotropism)1 Mark

Tara and Vijay set up the experiment with soaked bean seeds planted in different orientations (micropyle pointing up, down, left, right). What do you think they want to find out? How will they know if their hypothesis is correct?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Figure 10.3: Gravitropic Response Irrespective of Seed Orientation

1. Aim of the Experiment:
Tara and Vijay want to investigate: "Does the initial planting orientation or direction of a seed affect the direction in which its radicle (root) and plumule (shoot) emerge and grow?"

2. How Will They Know If They Are Correct?
• They will observe the seeds after 4 to 6 days of germination.
• In every single seed, regardless of whether it was planted pointing upwards, upside down, or horizontally sideways, the radicle always curves downward into the soil and the plumule always curves upward towards the air.
• This confirms their hypothesis that gravitational stimulus (geotropism) guides plant organ direction, not the physical orientation of the planted seed.

CBSE Board Marking Scheme 2026-27

Clear statement of scientific aim / question being tested1.5 Marks

Criterion for confirmation (observing roots grow down, shoots grow up in all orientations)1.5 Marks

Design a scientific experiment to investigate the effect of temperature on the germination of seeds. Describe the materials required, step-by-step procedure, expected observations, and conclusion.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Aim:
To determine how temperature affects the rate and percentage of seed germination in gram (chana) or moong seeds.

2. Materials Required:
3 identical Petri dishes or small bowls, moist cotton wool, 30 healthy soaked moong seeds (10 per dish), access to a refrigerator (cold, ~4 °C), an ordinary room (~22-25 °C), and a warm sunny area or incubator (~32-35 °C).

3. Step-by-Step Procedure:

Line all three Petri dishes with identical layers of wet cotton wool to ensure equal moisture.
Place 10 soaked moong seeds in each dish with equal spacing.
Dish A (Cold Environment): Place inside a refrigerator at 4 °C.
Dish B (Room Temperature / Moderate Warmth): Place on a table in the classroom at 22-25 °C.
Dish C (Excessively Hot / Warm): Place on a hot window sill or near a heat source at 38-40 °C.
Keep cotton moist in all dishes daily and record the number of sprouted seeds after 3 to 5 days.

4. Expected Observations:
• Dish A (Refrigerator): No germination or very sluggish emergence; cold temperature inhibits metabolic enzymes.
• Dish B (Room Temperature): Rapid and healthy germination; almost all seeds develop vigorous radicles and plumules.
• Dish C (Very Hot): Seeds dry out quickly or rot; poor germination.

5. Scientific Conclusion:
Seeds require an optimal moderate temperature (around 20 °C to 28 °C) for enzyme activity and cellular growth during germination. Extreme cold prevents germination by arresting metabolic reactions.

CBSE Board Marking Scheme 2026-27

Aim and materials required listed1 Mark

Controlled variable procedure with 3 temperature conditions1 Mark

Expected observations and biological conclusion on optimal temperature1 Mark

CBSE Competency-Based Question (Metamorphosis & Amphibian Biology Case Study)

Case Study: Adaptation and Metamorphosis in Pond Ecosystems:
During a monsoon ecology survey, students collected water samples from a local pond. They observed hundreds of tiny, fish-like tadpoles swimming actively using tails and breathing via external gills. Four weeks later, the pond began drying up, and they observed that the surviving creatures had grown four sturdy legs, lost their tails, and were leaping onto the muddy banks, breathing through lungs.
(a) What biological term describes this dramatic transformation from larva to adult?
(b) Why would an adult frog with gills have failed to survive once the pond dried up?
(c) Give one other example of an organism that undergoes a similar developmental transformation.

Detailed Analytical Solution & Marking Scheme

(a) Biological Term:
The transformation is called Metamorphosis (the process of rapid biological transformation from an immature larval form to an adult form in two or more distinct stages).

(b) Survival Significance:
Gills can only extract dissolved oxygen from liquid water. Once the pond dried up, gills would collapse and dry out, preventing oxygen uptake. Adult frogs develop lungs and moist skin to breathe atmospheric gaseous oxygen directly, allowing them to migrate and survive on land.

(c) Additional Example:
• Butterfly / Silk moth: Undergoes complete metamorphosis from caterpillar (larva) to pupa (chrysalis/cocoon) and finally into a winged adult butterfly.
• (Or Mosquito: Aquatic wriggler larva and pupa transform into a winged terrestrial/aerial adult).

Chapter 11: Nature's Treasures

NCERT Curiosity (Class 6) — Natural Resources, Renewable vs Non-Renewable, Forests, Fossil Fuels, Water & Soil Conservation, The 3Rs | CBSE 2026-27

📌 Key Environmental & Resource Concepts

Natural Resources: Materials, energy, and ecosystems provided freely by nature that sustain life and human civilization (Air, Water, Soil, Sunlight, Forests, Minerals, Fossil Fuels).
Classification by Exhaustibility:
- Renewable Resources: Inexhaustible or naturally replenished resources within human timescales (Sunlight, Wind, Biomass, Flowing water, Forests when managed sustainably).
- Non-Renewable Resources: Finite resources formed over millions of geological years that cannot be replenished once exhausted (Fossil fuels: Coal, Petroleum, Natural gas; Metallic minerals: Iron, Copper).
Ecological Importance of Forests: Lungs of the planet (oxygen producers & carbon sinks), soil binders against erosion, water catchments, and biodiversity habitats.
Conservation Framework (The 3Rs):
- Reduce: Minimize consumption and avoid waste.
- Reuse: Use objects repeatedly rather than discarding after single use.
- Recycle: Reprocess discarded paper, glass, plastic, and metals into new products.

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Unscramble the jumbled names of natural resources: (i) A T W R E, (ii) N D I W, (iii) R E F O S T, and (iv) O C R K. Classify each unscrambled resource as Renewable or Non-renewable with reasons.

[2.5 Marks]

✅ CBSE Standard Step-by-Step Solution

Jumbled Name	Unscrambled Resource	Resource Classification	Scientific Justification
A T W R E	WATER	Renewable Resource	Replenished continuously across Earth via the natural hydrological water cycle.
N D I W	WIND	Renewable Resource	Driven by inexhaustible solar heating of atmospheric air masses; never runs out.
R E F O S T	FOREST	Renewable Resource	Trees regenerate naturally from seeds and can be regrown sustainably through afforestation.
O C R K	ROCK	Non-Renewable Resource	Rocks and building stones take millions of years of geological tectonic processes to form.

CBSE Board Marking Scheme 2026-27

Each correct unscrambling and renewable/non-renewable classification0.5 Mark each + 0.5 Mark for justifications (Total 2.5 Marks)

State whether the following statements are True (T) or False (F). If False, correct them scientifically:
(i) Nature has all the resources needed to meet human needs, but not human greed.
(ii) Machines are a resource found directly in nature.
(iii) Natural gas is a non-renewable fossil fuel resource.
(iv) Air is an exhaustible non-renewable resource.

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(i) True. Mahatma Gandhi famously stated that nature provides enough to satisfy everyone's essential needs, but excessive over-exploitation and greed deplete resources.
(ii) False. Correction: Machines are human-made (artificial) resources constructed by humans using metals and natural materials; they are not found naturally.
(iii) True. Natural gas is a fossil fuel formed from buried prehistoric organisms over millions of years and cannot be replenished within human timescales.
(iv) False. Correction: Air is an inexhaustible renewable resource continuously recycled through photosynthesis and respiration.

CBSE Board Marking Scheme 2026-27

Each correct evaluation and rectification0.5 Mark each (Total 2 Marks)

Fill in the blanks using the most appropriate scientific terms:
(i) A liquid fossil fuel commonly used in two-wheelers like scooters and motorcycles is ________.
(ii) An abundant natural source of clean, renewable energy that powers the water cycle is ________.

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

(i) A liquid fossil fuel commonly used in two-wheelers like scooters and motorcycles is petrol (gasoline).
(ii) An abundant natural source of clean, renewable energy that powers the water cycle is solar energy (the Sun).

CBSE Board Marking Scheme 2026-27

Each correct fill in the blank0.5 Mark each (Total 1 Mark)

Classify the following as renewable or non-renewable resources: Coal, Natural gas, Forests, and Minerals (such as iron ore and copper).

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Renewable Resources:
• Forests: Living plant ecosystems that naturally reproduce, regrow, and can be sustainably harvested and replenished through afforestation.

2. Non-Renewable Resources:
• Coal: Fossil fuel formed from carbonized ancient plant remains over 300 million years; finite supply.
• Natural Gas: Gaseous fossil fuel trapped in deep subterranean rock strata; finite and non-replenishable.
• Minerals (Iron ore, Copper): Inanimate mineral ores formed by geological cooling of magma; non-replenishable once mined out.

CBSE Board Marking Scheme 2026-27

Classifying Forests as Renewable0.5 Mark

Classifying Coal, Natural gas, and Minerals as Non-Renewable with reasons1.5 Marks

Why do we say that petroleum is a non-renewable resource? Explain its geological origin and why rapid consumption poses an energy crisis.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Geological Origin of Petroleum:
Petroleum was formed from microscopic marine organisms (plankton, algae) that died millions of years ago and settled on ocean floors. Over hundreds of millions of years, they were buried under immense layers of silt and sand. Under intense geological heat, pressure, and absence of air, their biochemical remains were converted into crude petroleum oil.

2. Why it is Non-Renewable:
• The rate of petroleum formation is extraordinarily slow (millions of years).
• Human society is extracting and burning these reserves at millions of barrels per day.
• Because its rate of consumption is millions of times faster than its geological formation, petroleum reserves on Earth are strictly limited and will inevitably be exhausted in a few decades.

CBSE Board Marking Scheme 2026-27

Explaining millions of years geological formation from ancient marine biomass1.5 Marks

Contrasting ultra-fast consumption rate vs non-replenishable geological timeline1.5 Marks

"It is difficult to truly regrow a forest." Justify this statement scientifically. How does a natural virgin forest differ from a man-made tree plantation?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Justification:
A forest is not merely a collection of planted trees; it is a highly evolved, complex, self-sustaining climax ecosystem that took thousands of years to establish: 1. Soil Degradation & Humus Loss: When a forest is clear-cut, the delicate fertile topsoil rich in mycorrhizal fungi, earthworms, and organic humus is quickly eroded by wind and rain, making it harsh for new saplings.
2. Intricate Web of Biodiversity: Natural virgin forests host multi-tiered canopies (mosses, herbs, shrubs, understory, and emergent trees) supporting diverse insects, birds, and herbivores. A man-made plantation usually contains only single-species trees (monoculture like eucalyptus) and lacks true biodiversity.
3. Microclimate & Hydrology: Natural forests maintain local humidity, cloud condensation, and groundwater aquifers that cannot be replicated quickly by planting saplings.

CBSE Board Marking Scheme 2026-27

Loss of complex soil biology and humus layer1 Mark

Monoculture plantation vs multi-tiered diverse ecosystem distinction1 Mark

Disruption of microclimate, hydrology, and centuries-long ecological timeline1 Mark

Make an inventory of five natural resources you use directly or indirectly in your daily life. State one practical action for each resource that you and your family can take to conserve it.

[2.5 Marks]

✅ CBSE Standard Step-by-Step Solution

Natural Resource	Daily Life Application	Practical Conservation Action
1. Fresh Water	Drinking, cooking, bathing, washing	Turn off running taps while brushing; install aerators; harvest rainwater.
2. Petroleum (Fossil Fuel)	Fuel for family scooter/car; LPG for cooking	Use public transport, bicycles, or carpool; switch off vehicle engine at red lights.
3. Forest Wood / Paper	Notebooks, pencils, furniture, packaging	Use both sides of notebook sheets; recycle old newspapers; avoid paper cups.
4. Electricity (from Coal)	Lighting, fans, computer, refrigerator	Switch off fans and lights when leaving rooms; adopt LED bulbs and solar rooftop panels.
5. Soil	Growing agricultural food grains and vegetables	Compost kitchen organic peels to enrich soil; avoid littering non-biodegradable plastics on ground.

CBSE Board Marking Scheme 2026-27

Listing 5 resources with daily use and actionable conservation measure0.5 Mark each (Total 2.5 Marks)

Propose a practical, 3-point conservation action plan that students can implement in their school to reduce wastage of natural resources and adopt the 3Rs.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

School Conservation Action Plan (Based on the 3Rs):
1. Water Conservation (Catch the Rain & Fix Leaks): Establish a student "Water Brigade" to inspect taps across campus for leaks. Place collection buckets under RO water purifier drain pipes to reuse wastewater for mopping and watering school gardens.
2. Paper & Plastic Reduction (Zero-Waste Classroom): Strictly ban single-use plastic covers. Establish a two-bin waste segregation system in every classroom (Blue for clean dry paper, Green for food scraps). Compost canteen vegetable peels in an on-campus pit.
3. Energy Conservation (Solar & Switch-Off Protocol): Nominate classroom Energy Monitors responsible for turning off fans and LED lights whenever students leave for sports or library periods. Advocate for rooftop solar panels to power school computer labs.

CBSE Board Marking Scheme 2026-27

Three actionable, school-focused initiatives based on 3Rs and resource conservation1 Mark each (Total 3 Marks)

CBSE Competency-Based Question (Ecological Sustainability Case Study)

Case Study: Solar Micro-Grids in Remote Villages:
A remote hilly village in Ladakh was previously disconnected from the electrical power grid, forcing villagers to burn kerosene lamps and dried wood for light and heat, emitting smoke.
(a) Why is kerosene considered an unsustainable and health-hazardous fuel?
(b) What type of natural resource is solar radiation? State two major ecological benefits of installing rooftop solar panels.
(c) Explain how replacing wood burning with solar energy protects local mountain hillsides from soil erosion.

Detailed Analytical Solution & Marking Scheme

(a) Kerosene Hazards:
Kerosene is a non-renewable petroleum product. Burning it indoors releases harmful soot, particulate matter, and toxic carbon monoxide, causing severe respiratory and eye diseases.

(b) Solar Energy Benefits:
• Solar radiation is an inexhaustible renewable resource.
• Benefits: (1) Zero greenhouse gas emissions during operation (mitigates climate change), (2) Free fuel from the sun, eliminating continuous recurring fuel costs.

(c) Preventing Soil Erosion:
When villagers stop cutting down mountain trees and shrubs for firewood, the root networks remain intact in the soil. These roots bind the steep topsoil firmly, preventing rain and snowmelt from washing away fertile soil in landslides.

Chapter 12: Beyond Earth

NCERT Curiosity (Class 6) — Celestial Bodies, Moon Phases, Solar System, Planets, Stars & Constellations | CBSE 2026-27

📌 Key Astronomical Concepts & Celestial Mechanics

Celestial Bodies: Natural objects outside Earth's atmosphere: Stars, Planets, Satellites, Asteroids, Comets, and Meteoroids.
Stars vs Planets:
- Stars: Self-luminous celestial balls of burning hot gases producing their own light and heat by nuclear fusion (e.g., Sun, Sirius, Polaris). Stars appear to twinkle due to atmospheric refraction.
- Planets: Non-luminous celestial bodies orbiting a star in fixed elliptical orbits; reflect sunlight (e.g., Earth, Mars, Jupiter). Do not twinkle.
The Solar System: The Sun (central star) + 8 Planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) + Dwarf planets (Pluto) + Moons + Asteroids and Comets.
The Moon (Earth's Natural Satellite):
- Takes ~27.3 days to revolve around Earth (and 29.5 days between successive Full Moons).
- Phases of the Moon (New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent) occur because we see varying lit portions of the Moon illuminated by the Sun.
Constellations & The Pole Star: Identifiable patterns of stars (Ursa Major / Saptarshi, Orion). The Pole Star (Polaris) lies directly above Earth's North rotational axis and appears stationary in the northern sky.

NCERT Exercise: Let Us Enhance Our Learning (100% Textbook Questions)

Match the celestial items in Column I with their corresponding descriptions in Column II:
• Satellite of Earth
• Red planet
• Constellation resembling a hunter
• Planet commonly called the morning or evening star

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Celestial Item (Column I)	Matching Identity (Column II)	Astronomical Fact
Satellite of Earth	The Moon	Only natural satellite orbiting Earth at an average distance of ~384,400 km.
Red planet	Mars	Appears reddish-orange due to abundant iron oxide (rust) on its surface.
Constellation resembling a hunter	Orion (Mriga)	Prominent winter constellation with three bright stars forming a hunter's belt.
Morning / Evening star	Venus (Shukra)	Brightest planet in the sky; visible in western sky after sunset or eastern sky before dawn.

CBSE Board Marking Scheme 2026-27

Each correct matching with astronomical explanation0.5 Mark each (Total 2 Marks)

Solve the planetary alphabet riddle:
• My first alphabet is in MAN but not in CAN.
• My second alphabet is in ACE and also in FAN.
• My third alphabet is in RAT and not in CAT.
• My fourth alphabet is in SUN but not in FUN.
I am a planet that revolves around the Sun. Who am I?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Deduction Step-by-Step:
• First letter is in 'MAN' but not in 'CAN' → M
• Second letter is in 'ACE' and also in 'FAN' → A
• Third letter is in 'RAT' but not in 'CAT' → R
• Fourth letter is in 'SUN' but not in 'FUN' → S

Combining the letters: M - A - R - S = MARS.
Answer: The planet is MARS (The fourth planet from the Sun).

CBSE Board Marking Scheme 2026-27

Letter-by-letter derivation showing logic1 Mark

Final correct planet name: MARS1 Mark

Explain why the shape of the Moon appears to change continuously throughout a month (Phases of the Moon). Does the Moon actually change its shape? What is the duration of one complete lunar phase cycle?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Does the Moon actually change its shape?
No, absolutely not. The Moon is a permanent spherical rocky body whose actual physical shape remains constant.

2. Why Phases Occur:
• The Moon does not emit its own light; it reflects sunlight falling on its surface.
• At any given time, exactly one half (50%) of the Moon's spherical surface is illuminated by the Sun, while the opposite half is in dark shadow.
• As the Moon revolves around Earth in its orbit, our angle of view from Earth relative to the sunlit side changes continuously.
• We only see that portion of the illuminated half which faces directly towards Earth. This changing visible illuminated fraction gives rise to the phases of the Moon (from New Moon, Crescent, Half Moon, Gibbous, to Full Moon and back).

3. Duration:
The time taken from one New Moon (Amavasya) to the next New Moon is approximately 29.5 days (a synodic lunar month).

CBSE Board Marking Scheme 2026-27

Explaining that physical shape is constant sphere0.5 Mark

Scientific explanation of changing illuminated angle viewed from Earth1.5 Marks

Stating lunar cycle duration (~29.5 days)1 Mark

Which of the following is NOT officially classified as a major planet of our Solar System?
(i) Jupiter
(ii) Pluto
(iii) Neptune
(iv) Saturn

[1 Mark]

✅ CBSE Standard Step-by-Step Solution

Correct Option: (ii) Pluto
Scientific Reason: In 2006, the International Astronomical Union (IAU) reclassified Pluto as a Dwarf Planet because it has not cleared the neighborhood around its orbit in the Kuiper Belt. There are currently only 8 recognized major planets in our Solar System.

CBSE Board Marking Scheme 2026-27

Selecting option (ii) Pluto with IAU dwarf planet reclassification context1 Mark

Which is the brighter star as seen from Earth: the Pole Star (Polaris) or Sirius? Why does the Pole Star hold such immense navigational importance despite not being the brightest star?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Brighter Star:
Sirius (the Dog Star) is by far the brightest star in the entire night sky. The Pole Star (Polaris) is only of medium brightness (ranked around the 48th brightest star).

2. Navigational Importance of the Pole Star:
While all other stars appear to move across the night sky from East to West due to Earth's rotation, the Pole Star is situated directly along the imaginary northern extension of Earth's rotational axis.
Consequently, the Pole Star appears completely stationary in the sky throughout the night, pointing directly towards true geographic North. For millennia, sailors and desert travelers used it as an infallible compass guide to find true North.

CBSE Board Marking Scheme 2026-27

Identifying Sirius as the brighter star1 Mark

Explaining Pole Star's stationary position above North rotational axis for navigation1 Mark

List the correct sequential order of all eight planets in the Solar System in increasing order of their distance from the Sun. Differentiate between inner terrestrial planets and outer gas giants.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Sequential Order from the Sun:
1. Mercury → 2. Venus → 3. Earth → 4. Mars → 5. Jupiter → 6. Saturn → 7. Uranus → 8. Neptune.
Mnemonic: "My Very Educated Mother Just Served Us Noodles."

Classification into Inner and Outer Planets:
• Inner (Terrestrial) Planets [Mercury, Venus, Earth, Mars]: Closer to the Sun, made of dense rocky and metallic materials, have solid surfaces, few or no moons, and have no ring systems.
• Outer (Gas Giant / Ice Giant) Planets [Jupiter, Saturn, Uranus, Neptune]: Situated beyond the asteroid belt, massive in size, composed predominantly of hydrogen, helium, and frozen gases (methane/ammonia), have deep gaseous atmospheres, many moons, and ring systems.

CBSE Board Marking Scheme 2026-27

Listing all 8 planets in exact order of distance from Sun1.5 Marks

Contrasting Inner terrestrial vs Outer gas giant planets1.5 Marks

Explain how you can locate the Pole Star in the night sky using the constellation Ursa Major (Saptarshi / Big Dipper). Draw or describe the pointer stars method.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Method to Locate the Pole Star (Polaris) using Ursa Major:
1. Look towards the northern part of the night sky during summer nights and locate the prominent group of seven bright stars called Ursa Major (Saptarshi or the Great Bear).
2. The constellation resembles a large ladle, saucepan, or question mark, with three stars forming the handle and four stars forming the bowl (quadrilateral cup).
3. Look at the two bright stars located at the outer front rim of the cup (away from the handle). These two stars are called the Pointer Stars (Merak and Dubhe).
4. Imagine drawing a straight line passing through these two pointer stars from bottom to top.
5. Extend this imaginary line forward towards the north by about 5 times the distance between the two pointer stars.
6. This line leads directly to a medium-bright star standing isolated in that region of the sky. This star is the Pole Star (Dhruva Tara).

CBSE Board Marking Scheme 2026-27

Identifying Ursa Major / Saptarshi shape (ladle/cup of 7 stars)1 Mark

Identifying the two Pointer Stars at front of bowl1 Mark

Extending line ~5 times to locate stationary Pole Star (Polaris)1 Mark

Describe the surface features of the Moon. Why do footprints left on the Moon by Apollo astronauts remain unchanged even after decades?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

1. Surface Features of the Moon:
• The surface of the Moon is barren, dusty, and rugged.
• It is covered with numerous bowl-shaped depressions called craters, formed by collisions with meteoroids over billions of years.
• It has large dark flat basaltic lava plains called maria (seas) and steep rugged highlands/mountains.
• The Moon has no atmosphere (no air) and no liquid water.

2. Why Footprints Remain Unchanged:
On Earth, footprints are quickly erased by blowing wind, rainfall, flowing water, and human activity. Because the Moon has zero atmosphere, there is no wind to blow the dust and no rain to wash it away. In the complete absence of weather and erosion, footprints and rover tracks remain permanently preserved in lunar regolith for millions of years.

CBSE Board Marking Scheme 2026-27

Description of craters, dust, mountains, and absence of air/water1 Mark

Explaining lack of atmosphere means no wind or rain erosion to erase prints1 Mark

Why are large celestial bodies like the Sun, the Earth, the Moon, and other planets spherical in shape, while small space rocks (asteroids) have irregular, potato-like shapes?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

Scientific Explanation: Role of Self-Gravity:
1. Large Celestial Bodies (Planets and Stars): Objects with enormous mass possess immensely strong self-gravitational forces. Gravity pulls all matter equally from all sides towards the common center of mass. Over time, this uniform inward pull smooths out huge protrusions and forces the molten matter into hydrostatic equilibrium, which is geometrically a sphere.
2. Small Asteroids: Tiny space rocks have very little mass and therefore negligible self-gravity. Their weak gravitational pull is insufficient to overcome the mechanical rigidity of solid rock, allowing them to remain in irregular, jagged, potato-like shapes.

CBSE Board Marking Scheme 2026-27

Explaining intense self-gravity pulling equally towards center forming a sphere1 Mark

Explaining small asteroids lack sufficient mass/gravity to reshape rock1 Mark

Q10

When observing the night sky over several hours, stars appear to move slowly across the sky from East to West, but the Pole Star does not move.
(a) What causes the apparent East to West movement of stars?
(b) Why does the Pole Star appear stationary?

[2 Marks]

✅ CBSE Standard Step-by-Step Solution

(a) Cause of Apparent East to West Motion:
The stars do not actually orbit Earth every night. This apparent motion is caused by the Earth's axial rotation from West to East. Just as trees outside a moving train window appear to rush backwards in the opposite direction, the rotating Earth makes distant stationary stars appear to sweep across the sky from East to West.

(b) Reason Why the Pole Star Appears Stationary:
The Pole Star (Polaris) happens to be aligned almost perfectly with the imaginary axis of Earth's rotation directly above the North Pole. When a spinning top rotates, points located exactly along its central axis of rotation remain motionless while outer points spin around. Similarly, the Pole Star lies on Earth's rotational axis, making it appear fixed and unmoving in the northern sky.

CBSE Board Marking Scheme 2026-27

Explaining Earth's West-to-East axial rotation causes apparent East-to-West star motion1 Mark

Explaining Pole Star lies directly on Earth's rotational axis1 Mark

CBSE Competency-Based Question (Space Exploration Case Study)

Case Study: India's Chandrayaan-3 Lunar Landing:
On 23 August 2023, ISRO made history when the Chandrayaan-3 Vikram lander made a successful soft landing near the Moon's South Pole, deploying the Pragyan rover.
(a) Why did ISRO specifically choose the lunar South Pole region for scientific exploration?
(b) Can an astronaut hear the roaring engine of a rocket landing on the Moon from 50 metres away? Explain.
(c) Why do astronauts require pressurized spacesuits with oxygen supply when walking on the Moon?

Detailed Analytical Solution & Marking Scheme

(a) Strategic Importance of Lunar South Pole:
Deep craters at the lunar south pole lie in permanent shadow and never receive sunlight. Scientific data suggests these cold traps harbor vast deposits of frozen water ice, which can provide drinking water and be split into hydrogen and oxygen for rocket fuel in future deep-space missions.

(b) Hearing Sound on the Moon:
No, they cannot hear it. Sound is a mechanical longitudinal wave that requires a material medium (air, water, or solid) to propagate. Because the Moon has a total vacuum with no atmosphere, sound waves cannot travel through space.

(c) Necessity of Pressurized Spacesuits:
• Provides vital breathing oxygen.
• Maintains atmospheric pressure on the human body to prevent bodily fluids from boiling in the vacuum.
• Provides thermal insulation against extreme temperature swings ranging from +120 °C in lunar day to -130 °C in lunar night.

Chapter 1: Components of Food

NCERT Science (Classic) (Class 6) — Major Nutrients (Carbohydrates, Fats, Proteins, Vitamins, Minerals), Food Testing (Iodine, Biuret, Paper translucent test), Dietary Fibres & Water, Balanced Diet, Deficiency Diseases | CBSE 2026-27

📌 Key Concepts & Formulas

Carbohydrates & Fats: Energy-giving foods. Fats provide twice as much energy as carbohydrates.
Proteins: Body-building foods essential for growth and repair.
Vitamins & Minerals: Protective foods that defend the body against infectious diseases.
Deficiency Diseases: Scurvy (Vit C), Rickets (Vit D), Beriberi (Vit B1), Night blindness (Vit A), Goitre (Iodine), Anaemia (Iron).

NCERT Textbook Exercise & Practice Questions

Name the major nutrients in our food. Also name the nutrients which mainly give energy to our body, and the nutrient needed for growth and maintenance.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Classification of Major Nutrients:
• Major nutrients: Carbohydrates, Fats, Proteins, Vitamins, Minerals, Dietary Fibres (Roughage), and Water.
• Energy-giving nutrients: Carbohydrates and Fats.
• Nutrients needed for growth and maintenance: Proteins and Minerals.

CBSE Board Marking Scheme 2026-27

Listing all 5 nutrient classes + water and roughage1.5 Marks

Identifying energy-giving vs body-building nutrients1.5 Marks

Describe the chemical tests used in laboratory to detect the presence of: (a) Starch (Carbohydrate) (b) Protein in food sample.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Food Testing Procedures:
• (a) Starch Test: Add 2-3 drops of dilute iodine solution to the mashed food sample. Appearance of a blue-black colour confirms presence of starch.
• (b) Protein Test: Add 10 drops of water to food powder, then add 2 drops of Copper Sulphate solution and 10 drops of Caustic Soda (NaOH). Shake well. Development of a violet colour confirms presence of protein.

CBSE Board Marking Scheme 2026-27

Starch test: Dilute iodine -> Blue-black colour1.5 Marks

Protein test: Copper sulphate + Caustic soda -> Violet colour1.5 Marks

Fill in the blanks: (a) _____ is caused by deficiency of Vitamin D. (b) Deficiency of _____ causes a disease known as Beriberi. (c) Deficiency of Vitamin C causes a disease known as _____. (d) Night blindness is caused due to deficiency of _____ in our food.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Deficiency Diseases:
• (a) Rickets is caused by deficiency of Vitamin D.
• (b) Deficiency of Vitamin B₁ causes Beriberi.
• (c) Deficiency of Vitamin C causes Scurvy.
• (d) Night blindness is caused due to deficiency of Vitamin A.

CBSE Board Marking Scheme 2026-27

Correct blanks: Rickets, Vitamin B1, Scurvy, Vitamin A3 Marks

CBSE Competency-Based Case Study (NEP 2020)

Public Health Case Study: Mid-Day Meal Nutritional Balance:
In a rural school, students showed symptoms of bleeding gums, weak bones, and persistent fatigue. (a) Identify the likely nutrient deficiencies. (b) Recommend dietary modifications using locally available affordable food items.

Detailed Analytical Solution & Rubric

(a) Deficiencies: Bleeding gums indicate Vitamin C deficiency (Scurvy); weak bones indicate Calcium and Vitamin D deficiency (Rickets); fatigue indicates Iron deficiency (Anaemia).
(b) Diet Recommendations: Introduce amla, lemons, and guava (Vit C), green leafy vegetables like moringa/spinach (Iron), milk or fortified pulses, and ragi/millet porridge (Calcium).

Chapter 2: Sorting Materials into Groups

NCERT Science (Classic) (Class 6) — Objects Around Us, Properties of Materials (Appearance, Hardness, Solubility, Flotation, Transparency — Transparent, Translucent, Opaque) | CBSE 2026-27

📌 Key Concepts & Formulas

Lustre: Shine exhibited by freshly cut metals (Gold, Silver, Copper, Iron).
Solubility: Substances that dissolve completely in water (Salt, Sugar) vs Insoluble (Sand, Chalk powder).
Density / Flotation: Objects lighter than water float (Dry leaves, Wood, Oil); heavier objects sink (Coins, Pebbles).
Transparency: Transparent (Glass, Water, Clear air), Translucent (Oiled paper, Frosted glass), Opaque (Wood, Cardboard, Metal sheet).

NCERT Textbook Exercise & Practice Questions

Name five objects which can be made from wood. Select those objects from the following which shine: Glass bowl, Plastic toy, Steel spoon, Cotton shirt.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Material Identification:
• Objects made from wood: Table, Chair, Door, Bed, Bullock cart.
• Objects that shine (have lustre): Glass bowl and Steel spoon (Steel is a metallic alloy; clear glass reflects light with high gloss).

CBSE Board Marking Scheme 2026-27

Listing 5 wooden objects1.5 Marks

Identifying glass bowl and steel spoon1.5 Marks

Differentiate between transparent, translucent and opaque materials with two examples of each.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Optical Properties of Materials:
• Transparent: Materials through which light passes completely and objects can be seen clearly. Examples: Clear glass, pure water.
• Translucent: Materials through which light passes partially and objects cannot be seen clearly. Examples: Butter paper, frosted glass.
• Opaque: Materials through which light cannot pass at all and we cannot see through them. Examples: Wood, iron sheet.

CBSE Board Marking Scheme 2026-27

Clear scientific definitions of all three categories1.5 Marks

Two accurate real-life examples for each1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Commercial Packaging Engineering: Eco-Friendly Material Selection:
A beverage company wants to design a container for fresh orange juice. (a) Why is cardboard coated with wax preferred over plain iron cans? (b) Why are shopkeepers keen on displaying candies in transparent plastic or glass jars?

Detailed Analytical Solution & Rubric

(a) Waxed Cardboard: Iron reacts with citric acid present in orange juice (acid-metal corrosion causing food poisoning), whereas food-grade waxed paper is inert, lightweight, and impermeable to moisture.
(b) Transparent Jars: Transparency allows customers and children to easily see the confectionery without opening the containers.

Chapter 3: Separation of Substances

NCERT Science (Classic) (Class 6) — Methods of Separation: Handpicking, Threshing, Winnowing, Sieving, Sedimentation, Decantation, Filtration, Evaporation, Condensation, Saturated Solutions | CBSE 2026-27

📌 Key Concepts & Formulas

Solid-Solid Mixtures: Handpicking (size difference), Threshing (beating stalks to separate grain), Winnowing (wind separates lighter husk), Sieving (fine particles pass mesh).
Solid-Liquid Mixtures: Sedimentation (heavier solids settle down), Decantation (pouring clear liquid), Filtration (filter paper holds residue).
Solubility & Thermal Separation: Evaporation (liquid vaporizes leaving salt), Condensation (steam cools into liquid water).
Saturated Solution: A solution in which no more solute can be dissolved at that temperature.

NCERT Textbook Exercise & Practice Questions

Why do we need to separate different components of a mixture? Give two examples.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Purpose of Separation:
1. To remove harmful or non-useful substances: E.g., Small stones and dirt picked by hand from rice and pulses before cooking.
2. To obtain useful components: E.g., Churning curd or milk to obtain butter.
3. To obtain pure substances: E.g., Extracting common salt from seawater by evaporation.

CBSE Board Marking Scheme 2026-27

Stating removal of harmful substances + example1.5 Marks

Stating extraction of pure/useful components + example1.5 Marks

What is winnowing? Where is it used? How will you separate sand and water from their mixture?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Winnowing & Filtration:
• Winnowing: Method used to separate heavier and lighter components of a mixture by wind or blowing air. Used by farmers to separate light husk from heavy wheat grains.
• Separating Sand & Water:
1. Allow mixture to stand undisturbed: Heavy sand particles settle at bottom (Sedimentation).
2. Pour clear water gently into another beaker (Decantation).
3. Pass remaining liquid through a filter paper cone to retain sand particles on the paper (Filtration).

CBSE Board Marking Scheme 2026-27

Definition and agricultural use of winnowing1.5 Marks

Sedimentation, decantation, and filtration steps1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Municipal Water Treatment Plant: River Water Purification:
Turbid river water containing mud, suspended clay, and dissolved salts arrives at a water treatment plant. (a) Describe the step used to remove floating twigs and large debris. (b) Explain how alum helps settle colloidal clay particles (coagulation). (c) How are dissolved salts separated from water if drinking water is required?

Detailed Analytical Solution & Rubric

(a) Large Debris: Large physical bar screens (mechanical sieving/screening).
(b) Alum Coagulation: Alum particles neutralize negative electrical charges on fine colloidal clay particles, causing them to aggregate into heavier flocs that rapidly settle by sedimentation.
(c) Dissolved Salts: By Reverse Osmosis (RO) or Distillation (Evaporation followed by Condensation).

Chapter 4: Getting to Know Plants

NCERT Science (Classic) (Class 6) — Herbs, Shrubs, Trees, Creepers & Climbers, Parts of a Leaf (Petiole, Lamina, Veins, Venation — Reticulate & Parallel), Transpiration, Photosynthesis, Roots (Taproot & Fibrous), Flower Anatomy (Sepals, Petals, Stamens, Pistil) | CBSE 2026-27

📌 Key Concepts & Formulas

Plant Habitats: Herbs (green tender stems), Shrubs (woody stem branching near base), Trees (thick hard stem branching high up).
Leaf Venation: Reticulate (netted, linked to taproot) vs Parallel (linear, linked to fibrous root).
Transpiration: Evaporation of water vapour from stomata in leaves.
Flower Structure: Sepals (outer green calyx), Petals (coloured corolla), Stamen (male organ: anther + filament), Pistil (female organ: stigma + style + ovary with ovules).

NCERT Textbook Exercise & Practice Questions

Differentiate between herbs, shrubs and trees with two examples of each. What are creepers and climbers?

[4 Marks]

✅ CBSE Standard Step-by-Step Solution

Classification of Plants:
• Herbs: Small plants with green, soft and tender stems, usually short with few branches. Examples: Tomato, Wheat, Grass.
• Shrubs: Medium-sized plants with hard, woody stems branching out near the base. Examples: Rose, Lemon, Hibiscus.
• Trees: Tall plants with a thick, hard, brown woody trunk branching high above ground. Examples: Mango, Neem, Banyan.
• Creepers: Plants with weak stems that cannot stand upright and spread on ground (e.g., Pumpkin, Watermelon).
• Climbers: Plants with weak stems that take support of neighbouring structures to climb up (e.g., Money plant, Pea plant).

CBSE Board Marking Scheme 2026-27

Herbs, shrubs, trees definitions and examples2.5 Marks

Creepers and climbers distinction1.5 Marks

What is transpiration? Describe an activity using a polythene bag to demonstrate transpiration in plants.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Transpiration Demonstration:
• Definition: Transpiration is the biological process by which excess water is released from plant leaves into the atmosphere in the form of water vapour through microscopic stomatal pores.
• Activity:
1. Take a healthy potted plant kept in sunlight.
2. Enclose a leafy branch inside a clean, dry transparent polythene bag and tie its mouth firmly with thread.
3. Keep the plant in bright sunshine for 2 hours.
• Observation: Tiny droplets of water appear condensed on the inner walls of the bag.
• Conclusion: Water evaporated from leaves through transpiration.

CBSE Board Marking Scheme 2026-27

Scientific definition of transpiration1 Mark

Activity setup and polythene tying1 Mark

Observation of droplets and inference1 Mark

CBSE Competency-Based Case Study (NEP 2020)

Botanical Survey: Desert Flora Adaptation:
A botanist investigates an Acacia (Babool) and a Cactus in Rajasthan. (a) Why are leaves reduced to spines or thorns? (b) Which plant organ performs photosynthesis in a Cactus? (c) How do extensive taproots help desert shrubs survive long dry spells?

Detailed Analytical Solution & Rubric

(a) Leaf Reduction: Leaves are reduced to spines to eliminate water loss through transpiration and protect the plant from grazing herbivores.
(b) Photosynthesis: The green, fleshy stem takes over photosynthesis and contains chlorophyll.
(c) Taproots: Deep taproots penetrate dozens of metres into the subsoil to tap into deep groundwater aquifers.

Chapter 5: Body Movements

NCERT Science (Classic) (Class 6) — Human Skeleton & Cartilage, Joint Mechanics (Ball and Socket, Hinge, Pivotal, Fixed Joints), Muscles & Contraction, Locomotion in Animals (Earthworm, Snail, Cockroach, Birds, Fish, Snakes) | CBSE 2026-27

📌 Key Concepts & Formulas

Ball and Socket Joint: Allows movement in all directions (Shoulder and Hip joints).
Pivotal Joint: Cylindrical bone rotates in a ring (Neck joint where head joins neck).
Hinge Joint: Allows movement only back and forth like a door hinge (Elbow and Knee).
Fixed Joint: Bones cannot move (Cranium / upper jaw in skull).
Animal Locomotion: Earthworm (hydrostatic skeleton & bristles), Snail (muscular foot), Fish (streamlined body & caudal fin), Snake (curving loops).

NCERT Textbook Exercise & Practice Questions

Fill in the blanks: (a) The joint where our neck joins the head is a _____ joint. (b) The joint at the elbow is a _____ joint. (c) The contraction of the _____ pulls the bones during movement. (d) The skull bones are joined by _____ joints.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Skeletal System Blanks:
• (a) The joint where our neck joins the head is a pivotal joint.
• (b) The joint at the elbow is a hinge joint.
• (c) The contraction of the muscle pulls the bones during movement.
• (d) The skull bones are joined by fixed joints.

CBSE Board Marking Scheme 2026-27

Correct answers: Pivotal, Hinge, Muscle, Fixed3 Marks

Explain how a fish moves in water. How does a snake slither forward?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Locomotion in Fish and Snake:
• Fish: Possesses a streamlined body shape which minimizes water resistance. During swimming, muscles on one side of the body contract, bending the body into a curve while the tail swings to the opposite side. The sudden jerk of the tail fin (caudal fin) propels the fish forward.
• Snake: Has a long backbone and interconnected thin muscles. The snake's body curves into multiple side-to-side loops. Each loop presses against the ground to give a forward push, moving the snake forward rapidly in a wave-like slithering motion.

CBSE Board Marking Scheme 2026-27

Streamlined shape and caudal fin mechanism of fish1.5 Marks

Backbone and lateral loop mechanics of snake1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Biomechanics & Sports Science: Knee Joint Rehabilitation:
An athlete suffers an injury to the knee ligament. (a) What type of joint is the knee, and what planes of motion does it allow? (b) Explain why muscles always work in antagonistic pairs (such as biceps and triceps) to move a limb.

Detailed Analytical Solution & Rubric

(a) Knee Joint: A hinge joint that allows movement restricted to one plane (flexion and extension, like opening and closing a door).
(b) Antagonistic Muscle Pairs: A muscle can only pull; it cannot push. Therefore, two muscles are required to move a bone in opposite directions: when one muscle contracts to pull the bone, the partner muscle relaxes; to return the bone, the partner contracts while the first relaxes.

Chapter 6: The Living Organisms — Characteristics and Habitats

NCERT Science (Classic) (Class 6) — Biotic and Abiotic Components, Terrestrial Habitats (Deserts, Mountains, Grasslands), Aquatic Habitats (Oceans, Ponds), Adaptations of Camel, Fish, Cactus & Mountain Animals, Characteristics of Life | CBSE 2026-27

📌 Key Concepts & Formulas

Habitat: The natural dwelling place where an organism lives and thrives.
Adaptation: Specific morphological and physiological features that enable an organism to survive in its environment.
Biotic Components (Living: Plants, Animals, Microbes) vs Abiotic (Non-living: Rocks, Soil, Air, Water, Sunlight).
Characteristics of Life: Cellular structure, Nutrition, Respiration, Growth, Response to Stimuli, Excretion, Reproduction, Movement.

NCERT Textbook Exercise & Practice Questions

How is a camel adapted to survive in a desert? How are fish adapted to survive in water?

[4 Marks]

✅ CBSE Standard Step-by-Step Solution

Organism Adaptations:
• Camel Adaptations:
1. Long legs keep the body away from the scorching heat of the sand.
2. Excretes very small amounts of concentrated urine and dry dung.
3. Does not sweat; can survive for days without drinking water.
4. Wide, padded flat hooves enable comfortable walking on loose sand.
• Fish Adaptations:
1. Streamlined spindle shape allows smooth swimming with minimal water friction.
2. Slippery scales and mucus coating protect the body.
3. Gills extract dissolved oxygen from water for respiration.
4. Flat fins and tail maintain balance and steer direction.

CBSE Board Marking Scheme 2026-27

Listing 4 camel desert adaptations2 Marks

Listing 4 fish aquatic adaptations2 Marks

What are the common characteristics of living things? Explain 'Response to Stimuli' with an example.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Characteristics of Living Beings:
1. Need food and energy. 2. Show growth. 3. Respire to release energy. 4. Respond to environmental stimuli. 5. Excrete metabolic wastes. 6. Reproduce their own kind. 7. Show movement.
• Response to Stimuli: Changes in our surroundings that make us respond to them are called stimuli. Example: When our hand accidentally touches a hot stove plate, we reflexively pull our hand away immediately. Similarly, leaves of Mimosa pudica (Touch-me-not plant) fold up instantly when touched.

CBSE Board Marking Scheme 2026-27

Listing core life characteristics1.5 Marks

Definition of stimuli and valid plant/animal example1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Alpine Ecology: Himalayan Snow Leopard Adaptations:
Snow leopards inhabit freezing craggy mountain slopes above 3,500 m altitude. (a) What adaptations protect their paws from freezing and slipping? (b) Why do mountain animals have a high concentration of red blood cells? (c) How does thick white-grey fur serve dual functions?

Detailed Analytical Solution & Rubric

(a) Paw Adaptations: Broad paws acting as natural snowshoes with thick fur on foot-pads providing insulation and grip on icy rocks.
(b) High RBC Count: At high altitudes, oxygen partial pressure is low; increased red blood cells allow efficient oxygen binding and cellular transport.
(c) Dual Function of Fur: Exceptional thermal insulation against sub-zero blizzards and camouflage against rocky snow terrain for stalking prey.

Chapter 7: Motion and Measurement of Distances

NCERT Science (Classic) (Class 6) — Story of Transport, Standard Units of Measurement, International System of Units (SI Units), Measuring Length with Ruler, Types of Motion (Rectilinear, Circular, Periodic, Rotational) | CBSE 2026-27

📌 Key Concepts & Formulas

Standard Unit: A unit of measurement that has a fixed value and does not change from person to person.
SI Units: Length (Metre, m), Mass (Kilogram, kg), Time (Second, s). 1 km = 1,000 m; 1 m = 100 cm; 1 cm = 10 mm.
Rectilinear Motion: Motion along a straight line (March-past of soldiers, falling apple).
Circular Motion: Motion along a circular path where distance from center remains constant (Hands of clock, blades of fan).
Periodic Motion: Motion that repeats itself at regular intervals of time (Pendulum, swing, strings of guitar).

NCERT Textbook Exercise & Practice Questions

Why can a pace or a footstep not be used as a standard unit of length? What is the SI unit of length?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Standard Units of Measurement:
• Footstep Variation: The length of a footstep, handspan, or cubit varies from person to person based on physical stature. If footsteps were used, the measured distance would differ depending on who measured it, leading to commercial confusion.
• SI Unit: The International System of Units (SI unit) of length is the Metre (m).

CBSE Board Marking Scheme 2026-27

Explanation of individual human variability1.5 Marks

Stating SI unit = Metre (m)1.5 Marks

Identify the type of motion in each case: (a) Motion of a child on a swing. (b) Motion of the needle of a sewing machine. (c) Motion of a vehicle on a straight road. (d) Motion of the wheel of a moving bicycle.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Classification of Motion:
• (a) Motion of a child on a swing: Periodic motion (and oscillatory motion).
• (b) Motion of needle of sewing machine: Periodic motion.
• (c) Motion of vehicle on straight road: Rectilinear motion.
• (d) Wheel of moving bicycle: Exhibits both Rotational motion (about its axle) and Rectilinear motion (advancing forward on road).

CBSE Board Marking Scheme 2026-27

Correct types for (a), (b), (c)1.5 Marks

Dual motion identification for bicycle wheel1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Precision Metrology: Industrial Measurement Accuracy:
While measuring the length of a metal rod with a broken ruler whose zero mark is damaged, a student aligns the end with the 2.5 cm mark and reads the other end at 18.2 cm. (a) What is the true length of the rod? (b) State two essential precautions to avoid parallax error while reading a ruler.

Detailed Analytical Solution & Rubric

(a) True Length: Actual Length = Final Reading - Initial Reading = 18.2 cm - 2.5 cm = 15.7 cm.
(b) Precautions:
1. Keep the eye positioned vertically directly above the point where the measurement is taken.
2. Place the ruler strictly parallel and in contact along the edge of the object being measured.

Chapter 8: Light, Shadows and Reflections

NCERT Science (Classic) (Class 6) — Luminous & Non-Luminous Objects, Transparent, Translucent & Opaque Objects, Formation of Shadows, Pinhole Camera Mechanics (Inverted Images), Mirrors and Law of Reflection | CBSE 2026-27

📌 Key Concepts & Formulas

Light travels in straight lines (Rectilinear propagation of light).
Shadow: Formed when an opaque object blocks the path of light. Requires: Light source, Opaque object, and Screen.
Pinhole Camera: Forms real, inverted, and coloured image of distant objects without glass lenses.
Reflection: Bouncing back of light rays from a polished surface (plane mirror).

NCERT Textbook Exercise & Practice Questions

Explain why shadows are dark regardless of the colour of the opaque object. What are the three essential conditions required to form a shadow?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Nature of Shadows:
• Darkness of Shadows: A shadow is simply a region of darkness formed where an opaque object completely blocks light from reaching a screen. Since no light falls in that blocked region, a shadow always appears black or dark grey, regardless of whether the object is red, yellow, or green.
• Three Essential Conditions:
1. A source of light.
2. An opaque object to obstruct the light rays.
3. A screen (ground, wall, cardboard) upon which the shadow falls.

CBSE Board Marking Scheme 2026-27

Scientific explanation that shadow is absence of light1.5 Marks

Three conditions: Source, Opaque body, Screen1.5 Marks

How does a pinhole camera work? What are the characteristics of the image formed by a pinhole camera?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Pinhole Camera Working:
• Principle: Based on the rectilinear propagation of light (light travels in straight lines).
• Light rays from the top of an object pass straight through the tiny pinhole and strike the bottom of the tracing paper screen; light rays from the bottom pass straight through and strike the top.
• Characteristics of Image:
1. Inverted (upside down).
2. Real (formed on a screen).
3. Shows the natural colours of the object.

CBSE Board Marking Scheme 2026-27

Rectilinear propagation principle1 Mark

Ray crossing explanation through pinhole1 Mark

Image features: Inverted, real, coloured1 Mark

CBSE Competency-Based Case Study (NEP 2020)

Solar Eclipse Astronomy: Natural Pinhole Cameras in Nature:
During a solar eclipse, round circular patches of light appear on the ground beneath a dense tree. (a) What acts as pinholes in this natural phenomenon? (b) What do the circular light patches represent? (c) Why is it dangerous to view the sun directly without solar filter goggles?

Detailed Analytical Solution & Rubric

(a) Natural Pinholes: The tiny irregular gaps between overlapping leaves in the dense tree canopy act as natural pinholes.
(b) Light Patches: They are real, inverted pinhole images of the Sun (displaying the crescent shape of the eclipsed sun).
(c) Safety Risk: Concentrated ultraviolet and infrared rays from direct sunlight focus on the eye's retina, causing permanent photochemical retinal burns (solar retinopathy).

Chapter 9: Electricity and Circuits

NCERT Science (Classic) (Class 6) — Electric Cell (Terminal Anode & Cathode), Electric Bulb & Filament, Closed & Open Electric Circuit, Electric Switch, Electrical Conductors & Insulators | CBSE 2026-27

📌 Key Concepts & Formulas

Electric Cell: Converts chemical energy into electrical energy. Has a positive (+) metal cap and a negative (-) flat metal disc.
Electric Bulb: Has a thin coiled wire called filament (made of Tungsten) that glows when current passes. Supported by two thick wires.
Electric Circuit: Complete closed conducting loop allowing current to flow from positive terminal to negative terminal.
Switch: A simple mechanical device that breaks or completes a circuit.
Conductors (allow electricity: Copper, Aluminium, Iron, Graphite) vs Insulators (do not allow: Rubber, Plastic, Wood, Glass).

NCERT Textbook Exercise & Practice Questions

Explain why the bulb does not glow in an open circuit. What happens when the filament of an electric bulb breaks?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Circuit Continuity:
• Open Circuit: An electric current requires an unbroken, continuous closed loop of conducting material from the positive terminal of the cell to the negative terminal. When the circuit is open (switch OFF or wire disconnected), the conducting path is broken, current ceases to flow, and the bulb does not glow.
• Fused Bulb: When the filament of an electric bulb breaks, the circuit inside the bulb is fractured. Because the path of current between the cell's terminals is broken, current cannot flow, and the fused bulb will not glow.

CBSE Board Marking Scheme 2026-27

Requirement of closed path for current1.5 Marks

Explanation of fused bulb breaking circuit1.5 Marks

Why should an electrician wear rubber gloves while repairing an electric switch at your home? Differentiate conductors and insulators.

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Electrical Safety & Materials:
• Rubber Gloves: Rubber is an electrical insulator. The human body is a good conductor of electricity. If an electrician touches a live wire with bare hands, electric current flows through the body to the ground, causing severe electric shock. Wearing rubber gloves breaks the circuit and protects the electrician.
• Conductors: Materials that allow electricity to flow through them freely (e.g., Copper, Aluminium, Iron).
• Insulators: Materials that do not allow electric current to pass through them (e.g., Rubber, Plastic, Glass).

CBSE Board Marking Scheme 2026-27

Explaining human conductivity and insulating role of rubber1.5 Marks

Definitions and examples of conductors vs insulators1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Electrical Hazard Safety: Home Appliances Installation:
During home wiring, an electrician uses copper wires coated with PVC plastic and plugs made of Bakelite. (a) What is the function of the copper core? (b) What is the function of the outer PVC coating? (c) Why is water hazardous near electrical switchboards?

Detailed Analytical Solution & Rubric

(a) Copper Core: High electrical conductivity allowing efficient electrical energy transmission with minimal resistance.
(b) PVC Coating: Acts as an insulator preventing electric shock when handling cables and preventing short circuits if wires touch.
(c) Water Hazard: Tap water contains dissolved minerals and salts, making it a good conductor of electricity. Water near switches can conduct electricity to human hands, causing fatal electric shocks.

Chapter 10: Fun with Magnets

NCERT Science (Classic) (Class 6) — Discovery of Magnets (Magnes shepherd), Magnetic and Non-Magnetic Materials, Poles of Magnet (North and South), Magnetic Compass for Navigation, Attraction and Repulsion Rules, Caring for Magnets | CBSE 2026-27

📌 Key Concepts & Formulas

Magnetic Materials: Attracted by a magnet (Iron, Nickel, Cobalt). Non-magnetic: Wood, Plastic, Glass, Copper.
Poles: Regions near the two ends of a magnet where magnetic attraction is strongest (North Pole N and South Pole S). Poles always exist in pairs.
Law of Magnetic Poles: Like poles repel each other (N-N or S-S repel); Unlike poles attract each other (N-S attract).
Direction Finding: A freely suspended bar magnet always aligns in the North-South direction.

NCERT Textbook Exercise & Practice Questions

Where are the poles of a bar magnet located? How will you find the north pole of a magnet if it is not marked?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Poles & Direction Finding:
• Location of Poles: The poles are located at the two extreme ends of the bar magnet. Iron filings sprinkled on a sheet over a magnet accumulate most heavily at these two terminal points.
• Identifying North Pole:
1. Suspend the unmarked bar magnet freely from its center using a light thread so it can rotate freely in a horizontal plane.
2. Wait until the magnet comes to rest.
3. The end that consistently points towards the geographical North is its North-seeking pole (North pole); the opposite end pointing South is its South pole.

CBSE Board Marking Scheme 2026-27

Poles located at two extreme ends1 Mark

Free suspension method with thread1 Mark

Alignment with geographical North-South1 Mark

State the law of attraction and repulsion between magnets. How should magnets be stored safely to avoid self-demagnetization?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Magnetic Interaction & Storage:
• Law of Magnetic Poles:
1. Like poles repel each other (North repels North; South repels South).
2. Unlike poles attract each other (North attracts South).
• Safe Storage of Magnets:
1. Bar magnets should always be kept in pairs with opposite poles alongside each other.
2. They must be separated by a strip of wood.
3. Two pieces of soft iron (magnetic keepers) must be placed across their ends.
4. Never heat, hammer, or drop magnets from a height.

CBSE Board Marking Scheme 2026-27

Stating like poles repel, unlike poles attract1.5 Marks

Storage in pairs with keepers and wood separator1.5 Marks

CBSE Competency-Based Case Study (NEP 2020)

Maritime Navigation: Magnetic Compass Deviations:
A sailor navigates in open sea using a magnetic compass. (a) Why is the compass needle magnetized? (b) What happens if an iron tool box is placed near the compass? (c) How do magnetic levitation (Maglev) bullet trains utilize magnetic repulsion?

Detailed Analytical Solution & Rubric

(a) Compass Needle: The needle is a tiny, delicate pivot-mounted permanent magnet that aligns freely with Earth's magnetic field lines.
(b) Iron Proximity: The ferromagnetic iron tool box distorts the surrounding magnetic field lines, causing compass deviation (incorrect heading).
(c) Maglev Trains: Electromagnets on the train carriage and track have identical magnetic polarities facing each other. The powerful magnetic repulsion lifts the train 10 mm above the rail, eliminating friction and enabling speeds exceeding 500 km/h.

Chapter 11: Air Around Us

NCERT Science (Classic) (Class 6) — Atmosphere & Composition of Air (Nitrogen 78%, Oxygen 21%, Carbon Dioxide 0.04%, Water Vapour & Dust), Importance of Oxygen for Respiration & Combustion, Exchange of Gases in Plants & Animals, Wind Energy | CBSE 2026-27

📌 Key Concepts & Formulas

Atmosphere: Thick blanket of air surrounding Earth, extending up to hundreds of kilometres.
Composition of Air: Nitrogen (~78%), Oxygen (~21%), Carbon dioxide, Noble gases, Water vapour, and Smoke/Dust particles (~1%).
Oxygen: Supports burning and respiration. Nitrogen: Does not support burning.
Respiration in Organisms: Earthworms (breathe through skin), Fish (gills breathe dissolved oxygen), Plants (stomata exchange gases).
Carbon Cycle: Plants consume CO2 and release O2 during photosynthesis; animals consume O2 and exhale CO2 during respiration.

NCERT Textbook Exercise & Practice Questions

What is the composition of air? Which gas in the atmosphere is essential for respiration and burning? Describe an experiment showing that air contains oxygen.

[4 Marks]

✅ CBSE Standard Step-by-Step Solution

Atmospheric Composition & Oxygen Experiment:
• Composition: Nitrogen (78%), Oxygen (21%), Carbon Dioxide (0.04%), Argon, Water vapour, and Smoke/dust particles (remaining ~1%).
• Essential Gas: Oxygen (O₂) is essential for both respiration and combustion.
• Inverted Tumbler Experiment:
1. Fix a lighted candle in a trough filled with coloured water.
2. Cover the burning candle with an inverted glass tumbler.
3. Observation: After a few moments, the candle flame flickers and goes out, and water rises to fill approximately 1/5th of the tumbler's volume.
4. Conclusion: Oxygen occupied 1/5th (20%) of the air inside the tumbler; once consumed by combustion, burning ceased and water rose to occupy the vacuum.

CBSE Board Marking Scheme 2026-27

Volumetric composition of air1 Mark

Identifying oxygen1 Mark

Inverted glass tumbler candle experiment and inference2 Marks

How do plants and animals help each other in the exchange of gases in the atmosphere? Why do mountaineers carry oxygen cylinders?

[3 Marks]

✅ CBSE Standard Step-by-Step Solution

Ecological Gas Balance & High Altitude:
• Mutual Gas Exchange:
1. Animals consume oxygen during respiration and exhale carbon dioxide.
2. Green plants absorb carbon dioxide from air to prepare food by photosynthesis in sunlight and release oxygen back into the atmosphere.
3. Because plants produce far more oxygen during photosynthesis than they consume in respiration, the atmospheric balance between O₂ and CO₂ is maintained.
• Mountaineers: As altitude increases, atmospheric pressure drops and air becomes progressively thinner with lower oxygen density. To prevent altitude sickness and hypoxia, mountaineers carry oxygen cylinders.

CBSE Board Marking Scheme 2026-27

Photosynthesis vs Respiration ecological balance2 Marks

Thin air and low oxygen density at high altitude1 Mark

CBSE Competency-Based Case Study (NEP 2020)

Environmental Science: Urban Smog & Air Quality Index (AQI):
During winter months in metropolitan cities, a thick haze of smog blankets the city. (a) What two components combine to form smog? (b) Why are tall chimneys installed in factories with electrostatic precipitators? (c) Why do traffic police officers stationed at busy crossroads wear respirators?

Detailed Analytical Solution & Rubric

(a) Smog Composition: Smoke (unburnt carbon particles, sulfur dioxide) combined with Fog (condensed water droplets near ground level).
(b) Tall Chimneys: Discharge hot toxic gases and smoke high into the upper atmosphere away from human settlements, while electrostatic precipitators filter out 99% of particulate soot.
(c) Traffic Police Respirators: High concentration of vehicular exhaust contains toxic Carbon Monoxide (CO), nitrogen oxides, and fine PM2.5 particles that enter deep into pulmonary lung alveoli, causing respiratory disorders.