States of Matter — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. When ice is heated, it melts and becomes liquid water.
Melting is the process where a solid turns into a liquid when heat is added.
2. Cooling water vapor turns it back into a liquid through condensation.
Condensation is the process where gas cools down and changes into a liquid.
3. The change from liquid water to water vapor is called evaporation.
Evaporation is the process where a liquid changes into a gas when it is heated.
4. Freezing changes a liquid into a solid.
Ice is the solid form of water — its particles are packed tightly together in a fixed shape.
5. A gas spreads out to fill all the space in a container.
Gas particles move quickly in all directions and spread out to fill whatever space is available.
6. The particles in a solid are packed closely together.
Solid particles are packed closely together in a fixed arrangement, which gives solids their definite shape.
7. Heating a substance can change its state of matter.
Heat energy causes matter to change states — for example, heating a solid can turn it into a liquid.
8. Water droplets on a cold glass form through condensation.
The warm water vapor in the air cools when it touches the cold glass and turns into liquid droplets — this is condensation.
9. Oxygen in the air around us is a gas.
Steam is water vapor, which is water in its gas state — the particles move quickly and spread apart.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Solid
→ Definite shape and definite volume
Definite volume but no definite shape
Liquid
→ Definite volume but no definite shape
No definite shape or volume
Gas
→ No definite shape or volume
Definite shape and definite volume
Melting
→ Changing from solid to liquid
Changing from solid to liquid
A solid has definite shape and volume, a liquid has definite volume but takes the shape of its container, a gas has no definite shape or volume, and melting is the change from solid to liquid.