On a warm day, the temprature will be high and that will make the particles of water to possess more kinetic energy and to move faster. Because of the fast movement of the particles, some of them will be turned into gas, that is vapour. Because some of the water particles are turning into vapour, the concentration of the liquid water will be decreasing while that of the vapour will be increasing, until the equilibrium point is reached. At the equilibrium point, the forward and the backward rates are equal and the concentration of liquid water and vapour is the same.
