Question

Statement: At 0 Kelvin, crystals have a perfect orderly arrangement.
State whether the given statement is true or false.
A. True
B. False

Answer 1

Hint: We know that the degree of randomness in a system is measured in terms of entropy. Thus we can say that higher the entropy greater will be the disorder in the system. Therefore, the increasing order of molar entropy for the three phases of matter that is solid, liquid and gas is $\text{solid}<\text{liquid}<\text{gas}$.

Complete answer:
> In accordance with the third law of thermodynamics, at absolute zero that is at 0 K, a perfectly crystalline solid has a perfect order of its constituent particles, that is there is no disorder at all. Hence, we can say that the absolute entropy is taken as zero at 0 K.
> It is also known that, at absolute zero, the necessary requirement for the entropy to be zero is that for a perfectly ordered crystal the domains of the magnetic moments must be perfectly ordered. Therefore, it is true that the materials which are only ferromagnetic, antiferromagnetic and diamagnetic can satisfy this condition and thus, they possess the zero entropy at 0 K.
Thus, we can conclude that at 0 K crystals have a perfectly orderly arrangement.

Hence, the given statement is true.

Note: It is known that at 0 K, the material such as alloys which is the solution of at least two metals remain paramagnetic and may either have various ground states which are nearly degenerate or have dynamic disorder.