An experiment can be planned to measure the temperature change through continuous heating of a substance
Energy is needed to overcome forces of attraction between particles so temperature does not change when changing state
The change in state of pure substances can be seen on a heating/cooling curve as a horizontal line
There is a change of energy, arrangement, and organisation of particles of a pure substance at each stage

Keywords

Heating curve - shows temperature changes of a substance over time as it is heated.
Cooling curve - shows temperature changes of a substance over time as it is cooled.
Intermolecular forces - are forces between particles.

Common misconception

Pupils struggle to understand what is taking place at the horizontal parts of the graph.

Be concise with your language and ask pupils to use the same language. 'have enough energy to overcome the forces of attraction between particles', 'to slide past each other', 'to move past each other'.

Planning the experiment this lesson allows you to be ready for carrying it out in another lesson.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.

Sort the states of matter and the temperatures at which changes of state occur into the correct order, starting with a substance in the solid state.

1 - substance in the solid state

2 - melting point

3 - substance in the liquid state

4 - boiling point

5 - substance in the gas state

Q2.

Freezing and condensing are exothermic processes. Melting, evaporation and boiling are processes.

Correct Answer: endothermic

Q3.

A block of pure ice is heated in a beaker until it has all melted. Which of the following statements are correct?

All the ice will melt at the same time.

Correct answer: The ice will melt gradually over time.

The particles in water are different to the particles in ice.

Correct answer: The arrangement of the particles changes as the ice melts.

Correct answer: On average, the particles move faster as the temperature increases.

Q4.

Match the following keywords to their definition.

Correct Answer:melting,change from a solid state to a liquid state

change from a solid state to a liquid state

Correct Answer:boiling,change from a liquid state to a gas state

change from a liquid state to a gas state

Correct Answer:freezing,change from a liquid state to a solid state

change from a liquid state to a solid state

Correct Answer:condensing,change from a gas state to a liquid state

change from a gas state to a liquid state

Q5.

Which of the following statements describe what happens when a pure substance boils and changes from the liquid state to the gas state?

the change of state can happen over a range of temperatures

Correct answer: the change of state happens at an exact temperature

the temperature gradually decreases

Correct answer: the temperature remains constant

the temperature gradually increases

Q6.

Which of the following statements describes what happens when a pure substance freezes and changes from the liquid state to the solid state?

the temperature gradually decreases

Correct answer: the temperature remains constant

the temperature gradually increases

Correct answer: the change of state happens at an exact temperature

the change of state can happen over a range of temperatures

Exit quiz

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6 Questions

Q1.

Consider a heating curve (see image). The following statements are about some of the sections (e.g. ‘CD’ means the sloping part from C to D). Which of the statements are correct?

Correct answer: AB: temperature of pure solid substance increases as energy is transferred to it

Correct answer: AB: particles remain in fixed position but vibrations increase

Correct answer: BC: temperature does not change but particles start to move past each other

BC: temperature does not change but particles spread apart from each other

Correct answer: DE: temperature does not change but particles spread apart from each other

Q2.

The image shows three cooling curves. What do the ringed sections represent, in order from left to right?

condensing point; liquid state; freezing point

condensing point; liquid state; solid state

Correct answer: gas state; liquid state; freezing point

gas state; liquid state; solid state

gas state; melting point; freezing point

Q3.

Sort the following stages of a heating curve into the correct order, starting from a statement about the solid substance:

1 - Temperature of the solid substance increases until it reaches its melting point.

2 - Melting point: transferred energy is used to overcome forces of attraction.

3 - At the melting point, the temperature stays the same.

4 - Once all the substance is in the liquid state, the temperature rises again.

5 - Boiling point: transferred energy is used to overcome forces of attraction.

6 - At the boiling point, the temperature stays the same.

7 - Once all the substance is in the gas state, the temperature rises again.

Q4.

In a heating curve experiment, the dependent variable is temperature, and the independent variable is .

Correct Answer: time

Q5.

Which of the following pieces of equipment would you use to measure the dependent variable in the heating curve experiment?

beaker

boiling tube

Bunsen burner

stopwatch

Correct answer: thermometer

Q6.

The image shows a curve for oxygen. This is a , although it starts at the melting point rather than with the substance in the solid state.

Correct Answer: heating curve

Q1 UYSEG