With a rubber band fix a wad of cotton wool over the mercury bulb of a room thermometer. Note the temperature, damp the cotton wool with eau de cologne, and whirl the thermometer round on a string for a time. The temperature drops considerably. The alcohol in the eau de cologne evaporates quickly and so uses up heat. The draught caused by whirling the thermometer round accelerates the process and the heat consumption rises. In a refrigerator a chemical liquid evaporates in a container. The large amount of heat needed for this is taken from the food compartment.