Antifreeze is used in internal combustion engines and many other heat transfer applications, such as HVAC chillers and solar water heaters. The purpose of antifreeze is to prevent a rigid enclosure from undergoing physical stresses and catastrophic deformation due to the expansion that occurs when water turns to ice. Most antifreezes are chemical compounds made to be added to water to reduce the freezing point of the mixture below the lowest temperature that the system is likely to be exposed to.