Giving an example list two information which make a chemical equation more useful. (informative).

Explanation

(i) Physical state of reactants must be mentioned,
e.g. `2H _(2(g))+O_(2(g))to 2H_(2) O _((I)).`
(ii) Condition in which a reaction takes place is written on the arrow head,
e.g. `2H_(2(g))+O_(2(g))overset("burning")to2H_(2)O_((l))`