Physical States

When reading or writing a chemical equation, you will notice the indication of physical states. These are important for determining the form of the compound involved in the reaction.

We have four physical states:

1. Aqueous solution (aq): denotes water soluble substance
2. Solid (s): not water soluble
3. Liquid (l): pure liquid (typically H₂O)
4. Gas (g): pure gases formed (typically CO₂, H₂, NH₃ and SO₂)

As you become familiar with more chemical reactions, you will learn to recognize which compounds come in which physical states. For now, there are some guidelines to help you.

Determining Physical States:

1. If a substance is determined to be insoluble in water according to the solubility table, then you can classify it as solid (s).
2. If a substance is determined to be soluble in water according to the solubility table, then you can classify it as a liquid (aq).
3. The most common liquid you will encounter in basic chemistry is good old H₂O.
4. Become familiar with gas producing reactions, and you will get better at spotting gases. Here are few common ones to look out for: CO₂, H₂, NH₃ and SO₂