1.22 use the state symbols (s), (l), (g) and (aq) in chemical equations to represent solids, liquids, gases and aqueous solutions respectively

If a compound/atom/molecule is...

liquid, the state symbol is (l)

solid, the state symbol is (s)

gas, the state symbol is (g)

aqueous, the state symbol is (aq)

How to tell which state symbol to use... if your just given an equation, it may be hard to work out what is solid/liquid/gas/aqueous. Unfortunately there is no rule to learn that will give you the answer, but there are a few ways of working it out...

if a liquid (l) is heated, it will become a gas (g)
if a precipitate is formed, it will be a solid (s)
aqueous is anything dissolved in water, so if the compound contains an OH, it is most likely aqueous.