Year 8 Science · Unit 3 · Lesson 6

Heating, Cooling and Change of State

Apply Worksheet

Name

Date

Class

Learning Goals

Explain a refrigeration cycle using state changes and energy transfer.
Apply knowledge of boiling points and latent heat to cooking contexts.
Trace cause-and-effect chains through real-world heating and cooling scenarios.

Warm Up

Order the steps

Number the events from 1 to 6 to show the correct order of a refrigeration cycle. Event 1 = what happens first.

Order	Event
	The refrigerant condenses back to liquid outside the fridge, releasing heat to the room.
	Liquid refrigerant enters the inside of the fridge through an expansion valve.
	The refrigerant gas is compressed by a pump, raising its pressure and temperature.
	The cycle begins again — liquid refrigerant re-enters the fridge interior.
	The liquid refrigerant evaporates inside the fridge, absorbing heat from the food and air.
	The refrigerant leaves the fridge interior as a cool gas carrying absorbed heat.

Your Turn

Because… chain

Fill in the missing effects. Each cause leads to the next step in cooking pasta.

Water in a pot is heated on a stove

→

Water reaches its boiling point (100°C at sea level)

→

More heat is added but the temperature does not rise above 100°C

→

The energy goes into evaporating water (latent heat), not raising temperature

→

Overall outcome:

Show What You Know

1. A refrigerator keeps food cold by repeatedly evaporating and condensing a refrigerant liquid. Which of these two processes absorbs heat, and which releases heat? Explain using the idea of endothermic and exothermic changes.

Apply 3 marks

2. A pot of water boils vigorously but you keep the hotplate on maximum power. The water temperature does not climb above 100°C. Why not? What is happening to all that extra energy?

Apply 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?