Question

12. Although the actual volume of an ideal gas will be zero at 0 K, why is the volume of air not zero at this temperature?

A.Gases become liquid at very low temperatures.

B.Gas molecules repel each other more at low temperatures.

C.Gases are made out of molecules and they can never have a zero volume.

D.Gases expand as the temperature decreases.

Answer 1

Answer is option (C):Gases are made out of molecules and they can never have a zero volume.

Gases will no longer be a gas at absolute zero. As the gas is cooled, it will make a phase transition from gas into liquid, and upon further cooling from liquid to solid. Then the question comes, what are the atoms in the solid doing (if anything) at absolute zero. Are they totally motionless? The answer would be no. Atoms, being very tiny particles, must be analyzed using quantum mechanics. According to Heisenberg Uncertainty Principle, "the uncertainty of a particle's position and momentum (mass times velocity) are not independent of each other; the product of these uncertainties must be greater than a certain value.

Now, if the atoms were totally motionless, then both the position and momentum uncertainties would be zero, which is disobeying Heisenberg Uncertainty Principle.