STUDENT SPACE · TOPIC 2

States and changes of state

Describe the three states and use melting and boiling points to predict a state.

The essentials

Solids have a fixed shape and volume. Liquids have a fixed volume but take the shape of their container. Gases fill their container.
Melting and boiling require energy; freezing and condensation release energy.
Evaporation occurs at the surface below the boiling point. Boiling occurs throughout a liquid at its boiling point.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Water disappears from a wet floor at room temperature. Is this boiling or evaporation? Give one reason.

Need a hint for Question 1?

Think about where the change occurs and whether the water has reached its boiling point.

Check Question 1

Evaporation: water escapes from the liquid surface below its boiling point.

Name the changes from gas to liquid and from liquid to solid. State whether each releases or absorbs energy.

Need a hint for Question 2?

Think about cooling steam and then cooling water further.

Check Question 2

Gas to liquid is condensation; liquid to solid is freezing. Both release energy to the surroundings.

Why does a liquid take the shape of its container but keep almost the same volume?

Need a hint for Question 3?

Compare particle spacing with freedom of movement.

Check Question 3

Particles stay close together, so the volume changes little, but they move past one another and the liquid can flow.

For more written practice, use Lesson 2 in your worksheet. Your teacher will discuss those answers in class.

Compare solid, liquid and gas. Describe the spacing and movement of particles in each.