What actually happens on a microscopic level is that the atoms, for example, diatomic oxygen, hit the surface of the water, okay? When they hit the surface of the water, they bounce back with a higher kinetic energy, okay? So the oxygen gain kinetic energy while this lost kinetic energy, so it lost the heat. It lost energy because of conservation of energy, okay? Eventually, enough of these atoms will attack or hit the surface of the water that it will lose most of its energy, and this will cool it down, okay? And that's why convection can only occur in the presence of molecules.