5.1
Atoms and elements
Everything is made of atoms. An element has only one kind of atom, and each element has a symbol.
5.2
Compounds and formulae
A compound is made when atoms of different elements join. Its formula tells you which atoms, and how many.
5.3
Elements, compounds and mixtures
Air, sea water and juice are mixtures. Learn to tell elements, compounds and mixtures apart.
5.4
Reactions and conservation of mass
In a reaction, atoms are rearranged, never made or destroyed. So the total mass stays the same.
Daily 5
Five quick diagram questions a day from this unit. The ones you get wrong come back sooner. Progress saves in this browser.
What this unit covers
Mapped to the KS3 national curriculum (Chemistry: atoms, elements and compounds).
| Programme of study | Lesson |
|---|---|
| a simple (Dalton) atomic model | 5.1 |
| differences between atoms, elements and compounds | 5.1, 5.2, 5.3 |
| chemical symbols and formulae for elements and compounds | 5.1, 5.2, 5.4 |
| conservation of mass in changes of state and chemical reactions | 5.4 |
| mixtures (particle model) | 5.3 |