iirc it's more about the state of matter of the molecules being dissolved; As in oxygen is more soluble in cold water because it's a gas at room temp and salt is more soluble in hot water because it's a solid at room temp.

Excess heat energy in a liquid allows gas to escape easier, reducing solubility of gas in hot water. On the other hand, excess heat energy is needed in order to free more molecules from a solid like sodium chloride and keep them in solution.