When a substance changes state from a liquid to a gas, what happens to the spacing of its molecules?

When a substance transitions from a liquid to a gas, the molecules experience a significant increase in spacing. In a liquid state, the molecules are closely packed together, allowing for only slight movement relative to one another. When the substance boils or evaporates, the energy supplied to the liquid causes the molecules to gain kinetic energy, which overcomes the intermolecular forces holding them together. As a result, the molecules move more freely and become far more spread out compared to their arrangement in the liquid phase.

This expansion results in a gas having much greater molecular separation than a liquid. The change from a dense arrangement to a more dispersed one is not just minor; it is substantial, which is why the correct description of this change indicates that the spacing of molecules increases greatly. This understanding is essential in thermodynamics and refrigeration practices, as it relates to how gases behave under different temperature and pressure conditions.