Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters.

The purpose of antifreeze is to prevent a rigid enclosure from undergoing catastrophic deformation due to expansion when water turns to ice. Antifreezes are chemical compounds added to water to reduce the freezing point of the mixture below the lowest temperature that the system is likely to encounter. Either the additive or the mixture may be referred to as antifreeze.

An antifreeze mixture achieves freezing-point depression for a cold environment and also achieves boiling-point elevation to enable higher liquid temperatures. This is described as the action of a colligative agent, which can properly be referred to as both antifreeze and "anti-boil" when used for both properties. Careful selection of an antifreeze can enable a wide temperature range in which the mixture remains in the liquid phase, which is critical to efficient heat transfer and the proper functioning of heat exchangers.

Noun

antifreeze (countable and uncountable; plural antifreezes)

1. A substance, such as glycol, used to lower the freezing point of water; used as an additive in the radiators of motorcars.

• The plural form antifreezes is used only if more than one kind of antifreeze is meant.