Question

describe the conditions necessary for sublimation to occur.

Explanation:

Sublimation is the transition of a substance from solid to gas without passing through the liquid state. Key conditions: 1. Low atmospheric pressure (below the substance’s triple - point pressure, e.g., dry ice sublimes at 1 atm as its triple - point pressure is higher than 1 atm). 2. Appropriate temperature (the substance’s temperature should be such that the vapor pressure of the solid exceeds the surrounding gas pressure; for example, solid iodine sublimes when heated gently as its solid vapor pressure becomes sufficient at that temperature). Also, the substance should have a high vapor pressure in the solid state and weak intermolecular forces in the solid (so that molecules can escape directly into gas).

Answer:

Sublimation occurs when: 1. The atmospheric pressure is below the substance’s triple - point pressure (e.g., dry ice sublimes at 1 atm as its triple - point pressure is higher). 2. The temperature is such that the solid’s vapor pressure exceeds the surrounding gas pressure (e.g., solid iodine sublimes on gentle heating). Additionally, the solid should have relatively weak intermolecular forces and a relatively high solid - state vapor pressure.