A change in which no new substances are formed, such as a change in state, e.g. melting.

Occurs when a reaction takes place and atoms or ions in the reactants are rearranged to make new products/substances.

A model that helps us to understand physical properties of substances. It uses circles or spheres to represent particles, i.e. atoms or compounds.

A point at which we cannot use the model to help us explain a scientific phenomena.

Predicting states of matter and limitations of the particle model

Chemistry

The particle model

State changes: fundamentals

State changes: evaporation and sublimation

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

In the main image, the important information has been replaced with grey boxes. Which of the three answer images is an accurate representation of a chemical change of substances in the same state?

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

At which temperature are **all** of the following substances in a liquid state?

it has more than one type of atom in its molecules

it has strong covalent bonds in the molecules

it has stronger intermolecular forces between the particles

it has the biggest particles and they do not move

Three balloons are filled with neon, methane and oxygen, respectively (see image). Why would you expect the substance in the middle balloon to have the highest boiling point?

ionic substances have weak electrostatic forces of attraction

metallic bonds are the attraction between metal ions and delocalised electrons

particles are shown as solid spheres but are mainly empty space

small covalent substances have weak forces of attraction between molecules

the particle model does not show the movement or elasticity of particles

Which of the following statements are correct?

the model does not show attraction between particles which affects state change

the model shows metallic bonding incorrectly

the particles are all shown as having the same size

the particles are shown as inelastic spheres

The image shows the sublimation of carbon dioxide. What are some of the limitations of this representation?

do not take the shape of the container they are in.

have larger particles than all substances in a liquid state.

have particles which have no energy at all.

have particles that vibrate around their fixed positions.

Which of the following statements can correctly finish this sentence? Substances in a solid state ...

at their boiling point can form bubbles of the substance anywhere in the liquid.

have particles at the surface which may have enough energy to escape.

have particles that cannot move around and over each other.

take the shape of the bottom of the container they are in.

Which of the following statements can correctly finish this sentence? Substances in a liquid state …

are formed in the bubbles inside a liquid at boiling point.

have particles that are not attracted to each other at all, ever.

have particles that can escape an open container to fill all the space.

take the shape of the whole of the container they are in.

Which of the following statements can correctly finish this sentence? Substances in a gas state …

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

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

temperature where substance changes from liquid state to gas state

temperature where substance changes from gas state to liquid state

temperature where substance changes from liquid state to solid state

temperature where substance changes from solid state to liquid state

Match the following terms to their definitions.

Predicting states of matter and limitations of the particle model

Lesson outcome