Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Useful chemicals from crude oil

Rearrangement of atoms

In a chemical reaction, the substances that react together are called the reactants, while the substances that are formed are called the products.

reactants → products

The products have different properties from the reactants.

As a chemical reaction takes place, atoms in the reactants are rearranged to make the products. The number of atoms of each element in the reactants is the same in the products. No atoms are added or taken away. This is called the conservation of atoms.

When polythene is made from ethene, the polymer has the same number of carbon and hydrogen atoms as the ethene molecules it is made from.

Ethene makes polyethene

Back to Material choices index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.