The experiment shows that melting of ice requires relatively large amount of heat. Procedure is technically simple and straightforward, and yet allows to make sophisticated observations. Students take bags of ice brought to 0⁰ C by incubation in ice/water mixture and place them in hot water of a known mass. Temperature of water is measured before placement of ice, at the moment the melting is completed, and after the meltwater is mixed with the incubation water. The worksheet guides students to