When a substance changes from a solid state to a liquid state.

The process of a substance changing from a liquid state to a solid state.

A pulling force that keeps particles close together.

When a substance in the liquid state is heated, gas bubbles form and it changes to the gas state.

When a substance in the gas state is cooled and changes to a liquid state.

State changes: fundamentals

Chemistry

The particle model

State changes: evaporation and sublimation

Predicting states of matter

Pure substance

Heating and cooling curves

Heating curves: practical

In the Separating Substances unit, pupils will build on their knowledge of states of matter to learn about different techniques for separating mixtures.

In the Solid, Liquid and Gas States and Changes of State unit, pupils learned about the properties of different states of matter and how particles move during changes of state.

This unit covers the particle model, states of matter, and changes between them, distinguishing physical from chemical changes. It explains the concept of purity in scientific terms, using melting point data to identify pure and impure substances, and explores the limitations of the particle model.

States of matter

particles become free to move over and around each other

particles end up in a regular arrangement

Which of the following statements describe what happens during freezing?

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?

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

What is inside the bubbles of boiling water?

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?

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

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

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

a substance in liquid state changes to gas state

the temperature a substance changes from liquid state to gas state 

the temperature a substance changes from gas state to liquid state 

the temperature a substance changes from liquid state to solid state

the substance in solid state changes into liquid state

the temperature a substance changes from solid state to liquid state

Match the following key terms to their definitions.

particles start to align in a fixed arrangement

the temperature of the substance decreases

Which of the following statements describe what happens during condensing?

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

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

State changes: fundamentals

Lesson outcome