Question

What is the change in the state from gas to solid called?

Answer 1

Hint: There are various states of matter, like solid, liquid, and gas. These all states are inter – convertible when subjected to some specific conditions. When a gas changes directly to a solid, it does not liquefy. This phenomenon can be seen in nature, where water vapors convert directly to ice.

Complete answer:
The inter conversion of the states of matter results in the change of solid to liquid, liquid to gas. But a direct change can also occur, when a gas converts to a solid, or a solid converts to a gas. The basic process of conversion of states requires a temperature and a high pressure on which a gas is liquefied first and then made into a solid, or a solid is heated into a liquid then vaporized into a gas.
The direct change in state from gas to a solid is called as deposition. For this process to occur there should be no thermal energy in a gas. This is a thermodynamic process where the gas directly changes into a solid without getting converted to a liquid.
One of the examples of deposition is the process of snow formation in the clouds and frost on the leaves. The low temperature of the leaves in winters allows the water vapor to lose thermal energy and convert into a solid frost. Similarly, the snow is formed at a low temperature when moisture converts to ice.
Hence, the change in the state from gas to solid is called deposition.

Note:
The change from gas to solid is deposition, while the opposite of this, where a solid is directly converted into a gas is called sublimation. The transition process does not involve any liquid phase. The most common example of which is sublimation of naphthalene balls when kept in air becomes small with time as they sublime.