When a substance is heated, its average kinetic energy increases as the molecules move faster owing to the supply of energy. The solvent molecules are able to collide more frequently with the solute molecules and dislodge them so that the solute can dissolve in the solvent.
However, when a gaseous solute is dissolved in a liquid; as the temperature is increased and solvent molecules are able to collide more frequently with the solute molecules and dislodge them, gas molecules dissolved in the liquid are more likely to escape to the gas phase and not return due to the increase in their kinetic energy.
Hence, solubility of gas solutes in water decreases as temperature increases.
