Questions and Answers
1. Solids vs Liquids (Multiple Choice)
Question: The primary difference between solids and liquids is that constituent particles are: Answer: (i) closely packed in solids, while they are stationary in liquids is INCORRECT. Correct Option: (iv) closely packed in solids and move past each other in liquids. Reasoning: Solid particles vibrate but don’t move. Liquid particles are close but can slide past each other (flow).
2. True/False Statements
(i) Melting ice into water is an example of transformation of a solid into a liquid. (True) (ii) Melting process involves a decrease in interparticle attractions. (True) (iii) Solids have a fixed shape and a fixed volume. (True) (iv) The interparticle interactions in solids are very strong, and the interparticle spaces are very small. (True)
3. Removing particles from a chair
Question: If we remove all constituent particles from a chair, what happens? Answer: (iii) Nothing of the chair will remain. Reasoning: Matter is made of particles. If you remove the particles, you remove the matter itself. No matter = No chair.
4. Why gases mix easily but solids do not?
Answer: Gases have large interparticle spaces and the particles move rapidly in random directions. This allows particles of one gas to easily move into the spaces of another (Diffusion). Solids have particles tightly packed in fixed positions with very little space, preventing them from mixing easily.
5. Milk Spills vs Glass Tumbler
Question: Milk spreads, tumbler stays same shape. Justify. Answer:
- Milk (Liquid): Particles have weaker attraction and can slide past each other. It has no fixed shape and flows.
- Tumbler (Solid): Particles have strong attraction and fixed positions. It has a rigid, fixed shape.
6. Diagram: Ice to Water Vapour
(Draw three boxes)
- Ice: Particles packed in a tight grid.
- Water: Particles close but disordered/random.
- Vapour: Particles far apart, flying randomly.
7. Particle Representation
(i) Aluminium foil (Solid): Tightly packed, ordered lattice. (ii) Glycerin (Liquid): Loosely packed, random. (iii) Methane gas (Gas): Very spread out particles.
8. Candle Wax State (Fig 7.16)
- Fig 7.16a (Candle): Contains solid wax (body) and liquid wax (near wick) and gaseous wax (vapour burning).
- Matching:
- Solid wax Grid diagram.
- Liquid wax Loose packing diagram.
- Wax vapour Scattered diagram.
9. Ocean Water Salinity
Question: Why does it taste salty if salt is not visible? Answer: The salt particles have broken down into extremely tiny constituent particles (ions) and have occupied the microscopic interparticle spaces between water molecules. They are too small to be seen but exist in the solution.
10. Rice Grains: Solid or Liquid?
Question: Rice grains take the shape of the jar. Are they liquid? Answer: No, Rice is a Solid.
- Explanation: Each individual grain of rice has a fixed shape and volume. It does not flow like water. The “flow” of a pile of rice is just a collection of many small solids moving, not the particles within the rice changing position.