for the pressure. The kinetic energy U0 is a different type of kinetic energy to that associated with the particles in the excited states; since all of the particles in the condensate have the same energy, ≈0.77kTB, U0 is an ordered energy and the entropy associated with it is zero. The entropy of the system, at any temperature, is then determined by the random, thermal, motion of the particles in the excited states, and vanishes at T = 0 K, in accordance with the third law of thermodynamics.