Changes of state

 

Changes of state

An ice cube is a solid form of water. When it is heated, it changes its state from solid to liquid. This process is called melting. If the liquid water is heated more, it changes its state from liquid to gas. This process is called boiling. Changes of state can also happen in reverse if a substance is cooled down. For example, if gas is cooled down, it can change its state from gas to liquid. This process is called condensation. If liquid is cooled down, it can change its state from liquid to solid. This process is called freezing.

 

How water changes state

This diagram shows the process of water changing state.

 

 

Arrangement of particles

 

Solid

 

Liquid

 

Gas

 

 

 

🧪 Knowledge Check: Changes of State

Test your knowledge on how matter changes from one state to another.

1. Which process describes a liquid turning into a solid?

• Condensing
• Freezing
• Melting

2. What happens to the kinetic energy of particles when a substance is heated?

• The particles lose kinetic energy and move slower.
• The kinetic energy stays the same.
• The particles gain kinetic energy and move faster.

3. Which of the following is an example of a solid turning directly into a gas?

• Subliming
• Boiling
• Evaporating

4. Why is a change of state described as a 'physical change'?

• Because it creates a new chemical substance.
• Because no new substances are made and it is reversible.
• Because it only happens to living things.

5. During condensation, what happens to the particles in a gas?

• They gain energy and move further apart.
• They lose energy, move slower, and get closer together.
• They start vibrating in fixed positions.

Click to Reveal Answers

1. Freezing (The transition from liquid to solid).
2. Gain kinetic energy and move faster (Heating adds energy to the particles).
3. Subliming (Dry ice is a common example of this process).
4. No new substances are made (The substance stays the same, just in a different form).
5. Lose energy and get closer together (Cooling causes gas particles to form a liquid).

 

Summary:

 

• When solids, liquids and gases are heated or cooled, they change their form of matter.
• Substances can change their form of matter by processes like evaporation and boiling.
• The particle model is a way of showing how solids, liquids and gases change their form of matter.