Water containing propylene glycol is used as coolant in engines.

(a) Which property of water makes it a coolant?

(b) What is the advantage of adding propylene glycol to the water used as coolant?

(a) Water has a high specific heat capacity which is defined as amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius. This property is caused due the presence of hydrogen bonding among water molecules. The above property makes water as a e× cellent coolant as it takes long time to heat and cool water. This is the reason why land cools & heats faster than water.

Moreover, it is non-to× ic and non-poisonous and easily & cheaply available which gives it a superior advantage over other products.

(b) Adding propylene glycol (anti-freeze) to the water lowers the freezing temperature of the water due to Freezing point depression (is the decrease of the freezing point of a solvent on addition of a non-volatile solute). For e× ample, Sea Water (water + Salt) has a freezing temperature below 0°C and boiling point above 100°C. Because of it water can withstand cold temperature without freezing. Moreover, it also increases the boiling temperature of water.