The free energy of water is referred to as water potential. Water potential is also defined as chemical potential of water. The greater the concentration of water in a system, the greater is its kinetic energy or water potential. Water potential of the soil is quantised in terms of pressure. By convention, the water potential of pure water at standard temperature, which is not under any pressure, is taken to be zero. If some solute is dissolved in pure water, the solution has less free water molecules and the concentration of water decrease, reducing water potential.