There are two different and contradicting explanations given. Which one is correct?
Explanation 1: Cold air is more denser than hot air because ,when cold air of some density, say 'd' is heated, the molecules/atoms move apart from each other and so the volume expands. As mass of the air hasn't changes and the volume has increased, hot air is less denser than cold air.
Explanation 2: Hot air is more denser than cold air because ,air mostly comprises Oxygen(~20%) and Nitrogen(~78%). So this air, when starts holding water (i.e when it starts becoming cold), few O2(atomic mass 16 units) and N2(atomic mass 14 units) molecules are replaced by H20 (atomic mass 10 units). So, by Avogadro's law, for given volume of air at same temp and pressure and same number of molecules, cold air has lesser weight(H20 has lesser atomic mass) than hot air.
Which of the above two is correct? What causes sea breeze??
Is it that the second explanation is a special case of water acting as cooling agent, otherwise first case is true.