Question

Why are freezing, condensation and deposition exothermic processes?

Answer 1

Because all of these slow molecular motion, i.e. require the extraction of heat from the system.

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Exothermic by definition means the release of heat from a system. Any process that slows down the particles in the system due to heat flow outwards is therefore exothermic.

• Freezing has particles of a liquid slow down to form a lattice structure and become a solid phase.
• Condensation has particles of a gas slow down to form intermolecular forces and transition into a liquid phase.
• Deposition has particles of a gas slow down to form a lattice structure, becoming a solid and skipping the liquid phase.

Thus, the above three processes are exothermic with respect to the system.