Physical adsorption or physisorption When the particle of the adsorbate are held to the surface of the adsorbent by the physical forces such as vander Waal's forces, the adsorption is called physisorption. _ Physisorption is decreased on rising the temperature because on increasing temperature the kinetic energy of the gas molecules increases and they leave the surface of the adsorbent. On the other hand the rate of physisorption increases when temperature is decreased.