How does knowing the reactants and you classify a chemical reaction ?

The products. Without a balanced chemical equation, there is no reaction that can take place. The products is the final reation and the reactants help the final reaction take place. 

Evaporation: this is when warmth from the sun causes water from oceans, lakes, streams, ice and soils to rise into the air and turn into water vapour (gas). water vapour droplets join together to make clouds! condensation: this is when water vapour in the air cools down and turns back into liquid water.

Yes it would be a physical change.