Get authentic, complete, and scoring-oriented solutions for DAV Class 6 Science Chapter 3: Nature of Matter from the prescribed DAV Board textbook The Living World. Here you will find step-by-step verified answers to all questions in Something To Know (Sections A, B, C, D, E), structured 3-column comparison tables for states of matter, diffusion mechanisms, Value-Based Questions, and authentic DAV Board Examination Questions (PYQs).
⚛️ Chapter 3 Quick Revision & Key Concepts Summary:
- Definition of Matter: Anything that occupies space and has mass is called matter.
- Classification: The process of grouping objects based on similar physical or chemical properties is called classification.
- Three States of Matter: Solids (fixed shape and fixed volume), Liquids (fixed volume but no fixed shape), and Gases (neither fixed shape nor fixed volume).
- Diffusion: The spontaneous mixing of particles of two materials on their own due to free movement of particles. Rate of diffusion is fastest in gases, moderate in liquids, and slowest/negligible in solids.
- Transparency Classification: Transparent (allows light to pass through completely, e.g., clear glass, pure water), Translucent (allows partial light to pass through, e.g., frosted glass, butter paper), and Opaque (does not allow any light to pass through, e.g., wood, cardboard, iron wall).
- Solubility: Maximum mass of a solute that dissolves in a fixed volume of a solvent at a specific temperature. Solubility of most solids in water increases with an increase in temperature.
Comprehensive 3-Column Comparison: States of Matter
| Property / Parameter | Solids | Liquids | Gases |
|---|---|---|---|
| 1. Particle Packing | Very closely and tightly packed | Less closely packed than solids | Very loosely packed; far apart |
| 2. Inter-particle Space | Negligible (minimum) | Moderate | Maximum |
| 3. Force of Attraction | Strongest | Moderate (weaker than solids) | Weakest (almost negligible) |
| 4. Shape & Volume | Fixed shape and definite volume | No fixed shape, but definite volume | No fixed shape and no definite volume |
| 5. Compressibility | Incompressible | Almost incompressible | Highly compressible |
A. Fill in the blanks.
1. The process of grouping objects with similar properties is called classification.
Explanation: Classification enables systematic identification and convenient study of various materials based on their common attributes.
2. Anything that occupies space and has mass is called matter.
Explanation: Space occupied is measured as volume, while the quantity of material present gives its mass.
3. In the gaseous state of matter, the constituent particles have very little hold on one another.
Explanation: The inter-particle forces of attraction in gases are negligible, permitting particles to move freely in all directions.
4. Light does not pass through a blackboard as it is an opaque object.
Explanation: Opaque materials absorb or reflect incident light completely, preventing light rays from passing through them.
5. Smell of a perfume reaches us by the process of diffusion.
Explanation: Perfume vapours mix spontaneously with air molecules due to the continuous random kinetic movement of gas particles.
B. Write True or False for the following statements.
1. Air is a man-made material.
Answer: False
Correction: Air is a natural material and a homogeneous mixture of naturally occurring gases including nitrogen, oxygen, argon, and carbon dioxide.
2. A thin polythene sheet is transparent.
Answer: True
Explanation: A thin clear polythene sheet allows light to pass through it almost completely, enabling us to see through it clearly.
3. Pebbles float on water.
Answer: False
Correction: Pebbles are made of dense rock material and have a density higher than water, so they sink in water.
4. Diffusion is the mixing of the particles of two materials, on their own.
Answer: True
Explanation: Diffusion occurs spontaneously without any external mechanical stirring due to the natural kinetic energy of constituent particles.
5. Oxygen gas is slightly soluble in water.
Answer: True
Explanation: Oxygen dissolves in water in small quantities, which is vital for the survival and respiration of aquatic animals like fish.
C. Tick the correct option.
1. The state/states of matter, that have both a fixed shape and a definite volume, is/are—
(a) liquids only
(b) solids only
(c) gases only
(d) both liquids and solids
Answer: (b) solids only
Reason: In solids, constituent particles are held tightly in fixed positions by strong attractive forces, preserving both shape and volume.
2. Your book is made up of matter, because it—
(a) occupies space
(b) has some mass
(c) occupies space and has some mass
(d) can be touched
Answer: (c) occupies space and has some mass
Reason: The scientific definition of matter requires both occupying space (volume) and possessing mass.
3. Which of the following is an opaque material?
(a) a thin polythene sheet
(b) a sheet of plane glass
(c) clean water
(d) a piece of wood
Answer: (d) a piece of wood
Reason: Wood does not allow light to pass through it, creating a dark shadow behind it.
4. In which of the following cases would diffusion be the fastest?
(a) solid in another solid
(b) liquid in another liquid
(c) gas in another gas
(d) solid in a liquid
Answer: (c) gas in another gas
Reason: Gas particles possess maximum kinetic energy, high speeds, and maximum inter-particle spaces, resulting in the fastest rate of diffusion.
5. Which of the following is insoluble in water?
(a) common salt
(b) sugar
(c) mustard oil
(d) alcohol
Answer: (c) mustard oil
Reason: Mustard oil is immiscible and insoluble in water; it forms a separate upper layer because it is less dense than water.
D. Answer the following questions in brief.
1. Define the following:
(a) Natural materials: Materials that occur naturally in our environment and are obtained directly from nature without artificial chemical manufacturing (e.g., wood, cotton, water, rocks).
(b) Transparent materials: Materials that allow light to pass through them completely, allowing objects on the other side to be seen clearly (e.g., clear glass, clean water, air).
2. Name any three materials that are (i) transparent (ii) opaque in nature.
Answer:
• (i) Transparent materials: Clear sheet glass, clean water, and air.
• (ii) Opaque materials: Wood, iron sheet, and cardboard/brick wall.
3. Which state of matter (i) can (ii) cannot easily change its shape and volume? Why?
Answer:
• (i) Can easily change shape and volume: The gaseous state. This is because gas particles are widely separated, have negligible attractive forces between them, and move freely in all directions.
• (ii) Cannot easily change shape and volume: The solid state. This is because particles in a solid are very tightly packed with strong cohesive forces, holding them in fixed positions.
4. Why do materials diffuse into each other?
Answer: Materials diffuse into each other because their constituent particles are in continuous random motion and possess natural kinetic energy. Due to available inter-particle spaces, particles of one material enter into the spaces between particles of another material spontaneously.
5. Define the term ‘solubility’. How does it change on increasing the temperature of water?
Answer:
• Definition: Solubility is defined as the maximum mass of a solute (in grams) that can be dissolved in a given volume (typically 100 g or 100 mL) of a solvent at a specified temperature.
• Effect of Temperature: The solubility of most solid substances (like sugar and salt) in water increases as the temperature of water increases.
6. Name three materials that are (i) soluble (ii) insoluble in water.
Answer:
• (i) Soluble in water: Common salt (sodium chloride), sugar, and copper sulphate.
• (ii) Insoluble in water: Sand, chalk powder, and mustard oil.
E. Answer the following questions.
1. Why do solids have a fixed shape and a definite volume?
Answer: Solids possess a fixed shape and a definite volume due to the following structural properties:
1. Strong Inter-particle Attraction: The constituent particles in a solid are bound together by very strong intermolecular forces of attraction.
2. Negligible Inter-particle Space: The particles are closely packed with virtually no space to move from their locations.
3. Fixed Positions: The particles can only vibrate slightly about their mean positions and cannot slide past one another. Therefore, solids resist change in shape and volume under normal conditions.
2. Briefly describe an activity to show that pure water is a transparent liquid.
Answer:
• Apparatus: A clean glass beaker, pure water, and a coin.
• Procedure:
1. Place a coin at the bottom of an empty clean glass beaker.
2. Pour pure clean water into the beaker until it is three-fourths full.
3. Look down into the beaker from above in a well-lit room.
• Observation: The coin placed at the bottom is clearly visible with sharp details through the column of water.
• Conclusion: Since light travels straight through the water to our eyes without being blocked, pure water is proven to be a transparent liquid.
3. Describe an activity to show that a solid can diffuse slowly into a liquid.
Answer:
• Apparatus: A glass beaker, water, and crystals of potassium permanganate (KMnO4).
• Procedure:
1. Take a clean glass beaker and fill it half with clear water.
2. Place it on a steady table and let the water become completely still.
3. Carefully drop a few small crystals of potassium permanganate at the bottom of the beaker without stirring.
4. Observe the beaker continuously over several hours.
• Observation: Deep pinkish-purple streaks begin spreading upward and outwards from the crystals. Gradually, the entire volume of water turns evenly pink/purple.
• Conclusion: The constituent particles of solid potassium permanganate separate and move spontaneously into the inter-particle spaces of liquid water, demonstrating that solids can diffuse slowly into liquids.
4. What is a ‘saturated solution’? How can one prepare a saturated solution of common salt in water?
Answer:
• Definition: A solution in which no more solute can be dissolved at a given temperature is called a saturated solution.
• Preparation Steps:
1. Take about 50 mL of water in a clean glass tumbler at room temperature.
2. Add half a teaspoon of common salt to the water and stir thoroughly with a glass rod until the salt dissolves completely.
3. Add another half teaspoon of salt and stir again.
4. Continue adding measured half teaspoons of salt, stirring well after each addition.
5. A stage is reached when, despite thorough stirring, some salt particles remain undissolved at the bottom of the tumbler.
6. The clear solution above the undissolved salt is now a saturated solution of common salt at that temperature.
5. Suggest one activity to show the effect of temperature on the solubility of a solid in water.
Answer:
• Procedure:
1. Take two identical glass beakers, labelled ‘A’ and ‘B’, containing equal volumes (50 mL each) of water.
2. Keep Beaker A at normal room temperature. Heat Beaker B gently using a burner so that the water becomes hot.
3. Add one teaspoon of sugar to Beaker A and stir until dissolved. Keep adding sugar teaspoon by teaspoon until no more sugar dissolves and a saturated solution is formed at room temperature. Note the number of spoons added (say, 4 spoons).
4. Now, add sugar in the same manner to hot water in Beaker B, stirring continuously.
• Observation: You will observe that Beaker B dissolves significantly more spoons of sugar (say, 7 to 8 spoons) before reaching saturation.
• Conclusion: Heating increases the kinetic energy and inter-particle space of water molecules, proving that the solubility of a solid in water increases with an increase in temperature.
Value-Based Questions (VBQ) & HOTS (Higher Order Thinking Skills)
💡 Value-Based Question (VBQ):
Scenario: Meera visited her grandfather’s shop and noticed that all spices, pulses, and dry fruits were kept in transparent glass jars, while seasonal oils were kept in sealed tin containers. When asked, grandfather explained that transparent jars save time and prevent spoilage.
Values & Scientific Application:
1. Scientific Organization: Using transparent glass jars allows instant visual inspection of food items and prevents repeated opening, protecting goods from atmospheric moisture.
2. Protection from Sunlight: Storing oils in opaque tin containers prevents light-induced oxidation and rancidity, demonstrating wise practical application of material properties.
🧠 Higher Order Thinking Skill (HOTS):
Question: Why does the aroma of hot sizzling food reach you several metres away, but to smell cold food you have to go close?
Scientific Explanation: At higher temperatures, the constituent vapour particles of food possess high kinetic energy and move at significantly higher speeds. This causes rapid diffusion of food aroma particles into air molecules. In cold food, the kinetic energy of particles is low, so the rate of diffusion is extremely sluggish, requiring you to get close to detect it.
🎯 DAV Examination Corner: Authentic Board Exam Questions (PYQs 2022–23 & 2023–24)
Below are authentic questions directly retrieved from the DAV Public Schools Common Examination (Half-Yearly & Annual Board Papers) covering Chapter 3:
Q1. [DAV Half-Yearly Exam 2023–24 • 1 Mark Assertion-Reason]
ASSERTION (A): The science book of Std VI is a matter.
REASON (R): The book occupies space and has some mass.
Choose: (a) Both A and R are true and R explains A (b) Both A and R true, R doesn’t explain A (c) A is true, R is false (d) A is false, but R is true.
Model Answer: (a) Both A and R are true and R is the correct explanation of A. Anything that occupies space and has mass qualifies as matter; since the book satisfies both criteria, it is matter.
Q2. [DAV Half-Yearly Exam 2023–24 • 3 Marks SA-II]
Compare between solids and gases on the basis of their arrangement of particles, space between them, and the force of attraction between them.
Model Answer:
1. Arrangement of Particles: In solids, particles are closely packed in regular fixed patterns. In gases, particles are arranged in a completely disorderly manner and are far apart.
2. Inter-particle Space: Solids have negligible (minimum) space between particles. Gases have very large (maximum) space between particles.
3. Force of Attraction: Solids have very strong attractive forces that lock particles in place. Gases have extremely weak (negligible) attractive forces, allowing unrestricted movement.
Q3. [DAV Board Exam Model Practice • 2 Marks SA-I]
Why do aquatic organisms feel suffocated in warm water ponds during summer?
Model Answer: Unlike solids, the solubility of gases (like oxygen) in water decreases as temperature rises. In peak summer, pond water warms up, causing dissolved oxygen gas to escape into the air. The resulting depletion of dissolved oxygen makes aquatic respiration difficult.
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