When write chemical equations for reactions it is useful to know the state that the substances are in. We can do this by adding symbols that denote state after each substance in the equation. Here is a list of the four state symbols and what they mean:

·        (s) for solid

·        (l) for liquid

·        (g) for gas

·        (aq)[i] for in solution

So now we can write chemical equations like this:

[i] The aq comes from the Latin Aqueous meaning in water.