Question

Oxygen cannot be liquefied at room temperature by placing it under a large enough pressure to force its molecules together. Explain why this is.

Short answer

The critical temperature is a temperature of a substance in which it coexists with its solid, liquid, and gaseous phase at a certain pressure. Because of the high melting point, Oxygen remains gas at room temperature.

Step-by-step solution

Concept

The critical temperature is a temperature above which the liquid cannot exist. At sufficiently high pressure above the critical point, the gas will have the density of a liquid but it will not condense.

Liquification of Oxygen

All molecules have attractions between each other that result in the energy of liquefaction or vaporization. This energy is a result of electrons in one molecule attracting nuclei in another molecule from distortions of the electron clouds in collisions and is low for molecules with nonpolar bonds. Oxygen molecules are nonpolar therefore intermolecular energy of liquefaction is low.

At a given temperature some molecules have enough energy to escape from the liquid as the temperature is raised more and more can escape until above the critical temperature where gas cannot be liquefied.

The critical temperature of Oxygen is -118.4℃. Which is very very lower than room temperature. So at room temperature, it is difficult to liquefy the Oxygen.