Atoms and Reactions

- Atoms are the smallest particles of an element that take part in a reaction. All the atoms in an element are the same. They can't be created or destroyed in a reaction.

- Chemical properties describe how something behaves in a reaction. The properties are different for reactants and products. 

- If a reaction is in a container, the mass remains the same. 

- Physical properties can be solubility, melting point or density.

- Precipitation is 2 dissolved chemicals reacting to form a solid. 

- The number of atoms in reactants is the same as the number in the products, but rearranged.

- The law of conservation of mass is used to calculate the amount of oxygen in a sample. This involves:

 Weighing the sample (e.g. iron) and heating it with a known volume of air.

The mass of the product - the mass of the reactant = mass of oxygen used as reactant.