A simple particle model explains melting, boiling, freezing, and condensing processes.
Boiling is when a liquid becomes a gas throughout, forming bubbles. Condensation is when gas turns into liquid.
Melting is when a solid turns into a liquid with added energy. Freezing is the reverse: liquid to solid, losing energy.
The particles remain the same size and shape as they do not have bulk properties like melting and boiling points.

Keywords

Melting - When a substance changes from a solid state to a liquid state.
Freezing - The process of a substance changing from a liquid state to a solid state.
Forces of attraction - A pulling force that keeps particles close together.
Boiling - When a substance in the liquid state is heated, gas bubbles form and it changes to the gas state.
Condensing - When a substance in the gas state is cooled and changes to a liquid state.

Common misconception

Pupils often think that the particles within the liquid will have melted or boiled rather than remain the same size and shape, i.e. atoms do not have bulk properties like melting and boiling points.

Ensure that you specifically say that the particles themselves will not melt or boil.

Using the word 'state' when referring to a state of matter, e.g. liquid state. This helps pupils understand that substances can exist in different states of matter. For example, oxygen can exist in the gas state, liquid state or solid state.

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.

As particles gain energy, they are able to overcome the between them.

Correct Answer: forces of attraction

Q2.

For water, what is the temperature at which it turns from the liquid state to the gas state?

0°C

Correct answer: 100°C

50°C

–20°C

4°C

Q3.

Match the following key terms to their definitions.

Correct Answer:boiling,a substance in liquid state changes to gas state

a substance in liquid state changes to gas state

Correct Answer:boiling point,the temperature a substance changes from liquid state to gas state

the temperature a substance changes from liquid state to gas state

Correct Answer:condensing point,the temperature a substance changes from gas state to liquid state

the temperature a substance changes from gas state to liquid state

Correct Answer:freezing point,the temperature a substance changes from liquid state to solid state

the temperature a substance changes from liquid state to solid state

Correct Answer:melting,the substance in solid state changes into liquid state

the substance in solid state changes into liquid state

Correct Answer:melting point,the temperature a substance changes from solid state to liquid state

the temperature a substance changes from solid state to liquid state

Q4.

Which of the following statements describe what happens during condensing?

Correct answer: particles move closer together

particles start to align in a fixed arrangement

the particles become smaller

the temperature of the substance decreases

Correct answer: the volume of the substance decreases

Q5.

If a substance has a melting point of 50°C, at what temperature will it freeze?

-10°C

0°C

48°C

Correct answer: 50°C

100°C

Q6.

Models have limitations. What does this image of the particle model NOT attempt to show? Select all that apply.

arrangement of particles

Correct answer: movement of particles

Correct answer: forces between particles

Correct answer: elasticity of particles

Exit quiz

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6 Questions

Q1.

Which of the following statements describe what happens during freezing?

Correct answer: particles become fixed into position

particles become free to move over and around each other

particles end up in a random arrangement

Correct answer: particles end up in a regular arrangement

Correct answer: particles lose energy

Q2.

Imagine candles (wax melting point 65°C; boiling point 300°C) in a room at 25°C. The flames have just been extinguished (see image). What is the temperature of the melted parts?

somewhere around 25°C

somewhere between 25 and 65°C

exactly 65°C

Correct answer: somewhere between 65 and 300°C

somewhere above 300°C

Q3.

Which aspects of a particle change when a substance’s state of matter changes?

Correct answer: arrangement relative to other particles

Correct answer: energy of particle

Correct answer: movement of particle

shape of particle

size of particle

Q4.

What is inside the bubbles of boiling water?

air

nothing, only empty space

oxygen and hydrogen in the gas state

Correct answer: water in the gas state

Q5.

Commonly scientists only refer to melting and boiling points of substances. What is the state of matter of mercury at 25°C, if its freezing point is -39°C and condensing point is 357?

solid state

Correct answer: liquid state

gas state

none of the above

Q6.

Match the numbers in the image below with the correct state change.

Correct Answer:1,melting

melting

Correct Answer:2,boiling

boiling

Correct Answer:3,freezing

freezing

Correct Answer:4,condensing

condensing