Antifreeze (commonly ethylene glycol or propylene glycol) is usually mixed with water in the radiator of a car. What is its function and how does it work?

Answer 1

The ethylene glycol does two things. It depresses the freezing point of water to levels well below zero C and it raises the boiling point (along with the pressure allowed to build in the hot engine). These two serve as an antifreeze agent and operating at a higher temperature of the engine is higher efficiency.