b REACTIONS THAT TAKE IN HEAT ENERGY Put 10 mL of water in a testtube Read the temperature of the water Dissolve about 2 g of potassium nitrate in the water The temperature should fall through 90oC This means that in the process of dissolving in the water the particles have absorbed energy This energy has been taken from the surrounding water in the form of heat A similar result can be obtained by using potassium chloride instead