Have you ever wondered how antifreeze lowers the freezing point of water in the cooling systems of automobiles? French chemist,
Francois Raoult, discovered that the vapor pressure of a solvent was lowered by the addition of a solute and that the freezing points of solutions also were lowered. In addition, scientists now know that the boiling point is altered as well. The changes in the physical properties of a solvent due to the addition of one or more solutes are known as colligative properties. Today, automobile manufacturers make use of the principle of freezing point depression to protect engines from freezing in cold weather. Antifreeze, a non-electrolyte, is added to the water-filled radiator that cools the engine. Under most conditions, the presence of the antifreeze molecules in the water is sufficient to keep the system from freezing. Ethylene glycol is the major ingredient in automobile antifreeze, where its freezing point depression on water protects the cooling system against freezing and perhaps breaking the engine block. Freezing and Boiling Point of ethylene glycol in wate Ethylene glycol Concentration in water vs. freezing/boiling point % Weight EG Freezing Point°C Boiling Point°C 0 0 100 10 -4 102 20 -7 102 30 -15 104 40 -23 104 50 -34 107 60 -48 110 70 -51 116 80 -45 124 90 -29 140 100 -12 197 What does adding a solute, like ethylene glycol, do to a solvent, like water? A) lowers freezing point B) increases boiling point C) lowers boiling point and freezing point D) lowers freezing point; raises boiling point
