Does cold air have more oxygen than warm air?

Salt dissolves better in hot water than in cold water, but gases dissolve better in cold than in hot water.

The reason salt dissolves better in hot water, is that heated water molecules have greater kinetic energy. Since the molecules move around more, the attractions between water molecules are weaker, and salts are able to enter.

The reason gases dissolve better in cold water, is that gases want to escape water. However, they are trapped by the water molecules. When the water is hot, the molecules move around more, and there is more space between them. Gases are then able to escape. When the water is cold, the molecules stick close together, and trap the oxygen.

In other Words, the same conditions that help salts dissolve in water, allow gases to escape water.