In the context of the Third Law of thermodynamics, what is true of real substances as they approach absolute zero?

As real substances approach absolute zero, their entropy approaches zero. This is in accordance with the Third Law of Thermodynamics, which states that as the temperature of a perfect crystal approaches absolute zero (0 Kelvin), its entropy, which is a measure of disorder or randomness, approaches a minimum value. In the case of a perfect crystal at absolute zero, the entropy is considered to be precisely zero, since there is only one way for the crystal to be arranged (the perfectly ordered state).

For real substances, while they may not behave as ideal crystals, they tend to follow a similar pattern. As temperature decreases, the molecular motion slows, leading to a reduction in disorder, which expresses itself as a decrease in entropy. The entropy does not become negative or infinite; rather, it tends toward zero because the system reaches a unique ground state with minimal molecular configurations at absolute zero.

It's important to note that not all substances attain that perfect ordering due to impurities and other factors, so actual values can reflect a non-zero constant value very close to zero, but fundamentally, the entropy of substances does decrease and approaches zero as they approach absolute zero in accordance with the principles of thermodynamics.