Introduction to chemical reactions

Chemical reactions make new chemicals. Atoms are rearranged during a chemical reaction, but the number of atoms does not change.

Exothermic and endothermic reactions

Exothermic reactions release energy into the surroundings, so they usually feel hot. Endothermic reactions are the opposite.

Writing word equations

Chemical reactions can be represented by word equations. Learn more in this KS3 Chemistry guide from Bitesize.

Writing symbol equations

Chemical reactions can be summarised using symbol equations. Learn more in this KS3 Chemistry guide from Bitesize.

Conservation of mass

During chemical reactions or a change of state, no atoms are created or destroyed. The total mass of chemicals before and after a reaction remains the same.

What is combustion?

Combustion is another name for burning. In a combustion reaction, fuel is burned and reacts with oxygen to release energy.

Thermal decomposition

Thermal means heat. Decomposing is the process of breaking down. Thermal decomposition is a chemical reaction that happens when a compound breaks down when heated.

Introduction to displacement reactions

In a displacement reaction, a more reactive element replaces a less reactive element from its compound.

How to make CO₂

A simple, step-by-step, visual guide showing you how to make CO₂.

How to make bread

A simple, step-by-step, visual guide showing you how to bake bread.

How to turn starch into glucose

A simple, step-by-step, visual guide showing you how to turn starch into glucose inside your mouth.

9 Classroom videos

We have a selection of great videos for use in the classroom