Question

I did a ester lab not too long ago I was wondering why we submerged the ester in cold water before we started to waft the smell towards us.

Answer 1

This was to ensure that the ester was properly formed as esterification is a reversible process. If it were still hot and you tried to waft the smell, chances are that the backward reaction could have been taking place and any esters formed would have been reconverting back into the acid and alcohol. If you leave it to cool however, since the reaction can only take place in heat, the esters would not be reconverted and you would be able to get a more accurate smell.