The states of matter are used to describe the three physical states that matter commonly exists in: the solid state, liquid state and the gas state.

The particle model is a model used to explain the physical properties of substances by describing the arrangement and movement of particles.

Forces of attraction are pulling forces that keep particles close together.

If you compress a substance, it can be made to take up less space than before. Substances in the gas state can be compressed.

The particle model

Chemistry

State changes: fundamentals

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

Forces of attraction act in all directions.

Forces of attraction vary in strength depending on the state of matter.

Forces of attraction vary in strength depending on the substance.

In a gas state, particles are held together by forces of attraction.

In a solid or liquid state, particles are held together by forces of attraction.

Which of the following statements about forces of attraction are correct?

Water can evaporate at temperatures below its boiling point (100$$^o$$C) because some of its particles have enough {{}} to overcome the forces of attraction between them.

particles are kept in a fixed position by forces of attraction

particles do not have enough energy to overcome forces of attraction

particles vibrate around their fixed positions

Which of the following statements about particles in the solid state are correct?

particles are kept close together by forces of attraction

particles can move past neighbouring particles

particles have enough energy to partially overcome forces of attraction

Which of the following statements about particles in the liquid state are correct?

particles can move quickly in all directions

particles exist in a regular  arrangement

particles have enough energy to completely overcome the forces of attraction

Which of the following statements about particles in the gas state are correct?

it will not take the shape of the container; it can flow and be poured

it will not take the shape of the container; it cannot be compressed

it can flow and be poured; it cannot be compressed

Which **two** of the properties in the table can apply to **two** different states (but not necessarily the **same two** states).

A substance in the liquid state has particles that are free to move past their neighbouring particles; this means that liquids can {{}} and can take the shape of the bottom of a container.

a substance with weak forces of attraction between particles

a substance with moderate forces of attraction between particles

a substance with strong forces of attraction between particles

Starting with the lowest, sort the following substances in order of increasing melting point.

The substance must be entirely in the solid state.

The substance must be entirely in the liquid state.

The substance could be in the solid or liquid state, or both simultaneously.

A substance has a melting/freezing point of 25$$^o$$C. If a sample of this substance is in a container at 25$$^o$$C, which of the following statements is correct?

There is {{}} between the particles of a substance in the gas state.

only vibrational movement around a fixed position

Match each of the following states to the correct description of the movement of particles in that state.

Water can evaporate at temperatures below its boiling point.

Water can only evaporate at its boiling point.

True or false? Water can evaporate at temperatures lower than 100$$^o$$C. Select a reason for your answer

The particle model

Lesson outcome