What term describes the transition of a gas directly to a solid?

The correct answer is deposition, which specifically refers to the process where a gas transforms directly into a solid without passing through the liquid phase. This phenomenon is observed in situations such as the formation of frost, where water vapor in the air cools and sublimates directly into ice crystals.

Deposition is an important concept in both physical chemistry and atmospheric science, as it describes how certain substances behave under specific temperature and pressure conditions. This contrasts with the other terms provided: evaporation pertains to a liquid turning into a gas, condensation describes the transition of a gas into a liquid, and freezing involves a liquid solidifying into a solid state. Each of these processes plays a key role in the states of matter, but deposition uniquely identifies the gas-to-solid transition.