Antifreeze and the Freezing Point of Water

Chlorine-based compounds play an important role in all of our lives. Ethylene glycol, or antifreeze, is one product of chlorine chemistry. While ethylene glycol (C2H6O2 ) itself does not contain chlorine, it can be produced from ethylene chlorhydrin, which is a compound that includes chlorine in addition to three other building block elements: carbon, hydrogen, oxygen (C2H5OCl).

Antifreeze lowers the freezing point of any liquid to which it is added by preventing ice crystals from forming properly. This experiment will illustrate how ethylene glycol keeps our car engines running during the winter months. Specifically, students will explore the effects antifreeze has on the freezing point of water.

Begin by introducing antifreeze to your class, preferably in store packaging. Ask the students if they know what it is used for and discuss the objective of the experiment: the exploration of the effect of antifreeze on the freezing point of water. Explain that ethylene glycol also is used to produce polyester which is an important component of fabrics, seatbelts, automotive parts, etc.


  • Antifreeze
  • Foam polystyrene cups
  • Glass vials
  • Crushed ice
  • Water
  • Salt
  • Themometer


  • Wear rubber gloves and safety goggles/eyeglasses when handling antifreeze.
  • Keep hands away from face during experiment.
  • Thoroughly clean all equipment, gloves and hands when finished. Dispose of antifreeze, ice and salt solution in sink followed by five-minute flush with cold water; dispose of other materials in trash.


  1. Students work in groups with foam polystyrene cups that contain a slurry of ice chips, water and salt. The two vials are inserted into the ice mixture. One vial is filled with water and the other with water and antifreeze. (Ask students to try varying ratios of water to antifreeze—1:1, 1:32, etc.).


  2. The students then periodically record the temperatures of each of the mixtures. The water-only vial will freeze or form ice crystals within 10-15 minutes. The students will observe that the termperature of the antifreeze/water mixture will drop well below freezing and remain a liquid.