Science 7 · Unit 2: Materials and their structure · Cambridge Lower Secondary Science Stage 7

Questions

1. 1. The particles in a liquid lose enough energy. What happens to the liquid?

   • It freezes into a solid.
   • It melts.
   • It boils into a gas.
   • It evaporates.
   Check

2. 2. Which describes the particles in a solid?

   • far apart, not moving at all
   • close together in a regular pattern, vibrating in fixed places
   • far apart, moving quickly in all directions
   • close together, sliding past each other
   Check

3. 3. The particles in a liquid gain enough energy. What happens to the liquid?

   • It stays a liquid but gets smaller.
   • It freezes into a solid.
   • It boils and becomes a gas.
   • It condenses.
   Check

4. 4. Which describes the particles in a gas?

   • far apart, moving quickly in all directions
   • touching, but able to slide past each other
   • touching, in a regular pattern
   • far apart, in a regular pattern
   Check

5. 5. Complete the sentence: for a solid to melt, its particles must ___ energy and vibrate ___.

   • lose … less
   • gain … more
   • lose … more
   • gain … less
   Check

6. 6. When a solid melts, the particles escape from the forces holding them in place. What can they do now?

   • stop moving altogether
   • move far apart and stop touching
   • move past each other
   • only vibrate on the spot
   Check

7. 7. Match each change of state to its name.

   • solid → liquid
   • liquid → solid
   • liquid → gas
   • gas → liquid

   • freezing
   • boiling
   • condensing
   • melting
   Check

8. 8. Ice is heated and melts. What happens to its particles?

   • They escape and spread far apart as a gas.
   • They lose energy and stop vibrating.
   • They melt into smaller particles.
   • They gain energy, vibrate more, break out of their fixed places and move past each other.
   Check

9. 9. An iron bar fits its holder when cold. After heating it no longer fits. Why?

   • The particles themselves get bigger.
   • More particles are made when it is heated.
   • The bar melts a little and spreads out.
   • Its particles vibrate more and take up more space, so the bar expands.
   Check

10. 10. In which states of matter do the particles NOT touch each other?

    • solid only
    • all three states
    • gas only
    • liquid and gas
    Check

11. 11. Which word matches this statement: when a gas is cooled to form a liquid?

    • condensation
    • melting
    • evaporation
    • freeze
    Check

12. 12. What do the particles in solids, liquids and gases all do?

    • vibrate
    • move freely from place to place
    • spread out to fill their container
    • stay perfectly still
    Check

13. 13. What do we call a liquid changing into a gas at its surface, below its boiling point?

    • freezing
    • condensation
    • evaporation
    • melting
    Check

14. 14. What can particles in liquids and gases do that particles in solids can't?

    • have energy
    • move from place to place
    • touch each other
    • vibrate
    Check

15. 15. A gas reaches a cold surface and changes into a liquid. Use particle theory to explain what happens.

    • The gas particles gain energy and stick to the mirror.
    • The mirror's particles turn into water.
    • The gas particles get bigger and heavier.
    • The gas particles lose energy on the cold surface, slow down and come close together as a liquid.
    Check

16. 16. A liquid is heated and changes into a gas. What happens to its particles?

    • They stop moving and fall to the bottom.
    • They gain energy, move faster and escape the forces holding them together, so they spread far apart.
    • They lose energy and move closer together.
    • They get bigger and stick together.
    Check