Question

Which of the following processes are exothermic, and which are endothermic and why?

1) Ice cubes solidify in the freezer

2) Dew forms on a lawn overnight

3) Ice cubes in a frost free-freezer slowly lose mass

Answer 1

1.Ice cubes solidifying to solid state from water is Exothermic in nature as water releases heat to surrounding to become ice cubes.

2. It's exothermic. The wet and warm air makes contact with cold grass or ground and turns to liquid from vapour giving out heat energy.

3.In a frost free freezer sublimation ( evaporation of solid ) takes place leading to shrinkage. The air is less than saturated with moisture which prevent icing. So frozen water moves into by directly turning to vapour without going through liquid phase. Hence it is an Endothermic reaction.