Question

How would you prove that the air we breathe out is warmer ?

Answer 1

Keep your palm in front of your mouth and blow some air. You will feel warm. This proves that the air that is breathe out is warmer. In place of hand you can also place a folded handkershief, you can feel that the place where you breathe out is warmer than the area which was not in contact with your breathe.

Answer 2

answer 1: assuming u meant how to prove it...

      just tell your partner to hold his/her hand over your nose while breathe out. he/she can sense the temperature to be warmer

answer 2: assuming you meant why is it warmer...

       formation of co2 in our body is one of the simplest exothermic { high energy yielding } process. it makes the air we breathe out warmer..

also... if you open you mouth while breathing out , due to joule-thompson effect, the air tends to be warmer

{joule-thomson effect : an ideal gas cools down if the pressure acted on the gas is suddenly reduced (or) when gas moves from highly pressurised valve(your mouth in this case) to a less pressure area, cools down.}

alternate to answer 1 :

  ...breathe on a glass surface, you ca see condensation droplets due to warm temperature of the air you breathe out...