Give the four symbols for physical states of reactants and products, and tell what each means.

We are going to use table salt, NaCl as an example.

(s) = solid, eg the salt you put on your food is a crystalline solid. 
(l)  = liquid, if you melt salt it take on a liquid form
(g)  = gaseous, if you put enough energy in the salt will turn into a gas.
(aq) = aqueous, meaning in water or another solvent. If you put some table salt in water and stir it, it will dissolve, the NaCl molecules dont get destroyed but they dissolve becoming part of the liquid. 

We first assume that this gas is an ideal gas where it follows the ideal gas equation. the said equation is expressed as: pv = nrt. from this equation, we can predict the changes in the pressure, volume and temperature. if the volume and the temperature of this gas is doubled, then the pressure still stays the same.