The table below lists the density of O₂ at various temperatures and at 1 atm. The normal melting point of O₂ is 54 K.
(b) Over what temperature range is O₂ a liquid?

Key Concepts

Phase Changes

Phase changes refer to the transitions between solid, liquid, and gas states of matter. For oxygen (O2), understanding these changes is crucial, particularly the melting point and boiling point, which define the temperature ranges where the substance exists as a solid, liquid, or gas. The melting point indicates the temperature at which O2 transitions from solid to liquid, while the boiling point marks the change from liquid to gas.

Density and Temperature Relationship

Density is defined as mass per unit volume and can vary with temperature. For gases like O2, density decreases as temperature increases, due to the increased kinetic energy of the molecules causing them to occupy more space. This relationship is important for determining the state of a substance at different temperatures, particularly when assessing whether O2 is in a liquid state at specific temperatures.

Critical Point

The critical point of a substance is the temperature and pressure at which the distinction between liquid and gas phases disappears. For O2, knowing the critical temperature helps in understanding the conditions under which it can exist as a liquid. If the temperature is below the critical temperature and above the melting point, O2 can exist as a liquid, which is essential for answering the question about its liquid state.