describe the conditions necessary for sublimation to occur.

Brief Explanations:

Sublimation is the transition of a substance directly from the solid - to the gas state, without passing through the liquid state. It occurs when the vapor pressure of the solid is greater than the partial pressure of the substance in the surrounding gas. This typically happens at low pressures (below the triple - point pressure of the substance) and can be facilitated by heating.

Answer:

Sublimation occurs at low pressures (below the substance's triple - point pressure) and can be aided by heating, when the vapor pressure of the solid exceeds the partial pressure of the substance in the surrounding gas.