Question

what is the implication of the third law of thermodynamics and the fate of the universe? (give evidence please)

Answer 1

The third law of thermodynamics is regarding the properties of system in equilibrium at absolute zero temperature. According to this law, the entropy of the perfect crystal is zero at absolute zero.

Consequences of third law:

1. The temperature of a substance can be reduced in an isentropic process by changing the temperature. Entropy difference at absolute zero can be obtained by finite number of steps in nuclear demagnetization process. But at T=0 there is no entropy difference. Hence, an infinite number of steps are to be required.

2. According to the third law of thermos dynamics, the specific heat of the substance always zero when it cooled to enough temperature.

The evidence for the third law of thermodynamics is as follows.

Water vapor has high entropy. As the water vapor cools it becomes liquid. The molecules in the liquid will moves around but not as free as the motion of the molecules in vapor. Hence, the entropy of the water decreases when compared to the vapor. If water cools further it becomes ice (solid). The solid water molecules can no longer move freely, but can only vibrate within the ice crystals. The entropy is very low. As the water is cooled to absolute zero, the vibration of the molecules reduces. If the solid water reached absolute zero, all molecular motion would stop completely. At this point, the water would have no entropy.