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

In an oxidation reaction, a substance gains oxygen atoms. Learn more in this KS3 Chemistry guide from Bitesize.

A catalyst is a substance that speeds up a chemical reaction. Catalysts are useful because they do not get used up during a reaction.

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

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

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

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.

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

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.

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

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

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