Based on the questions given, carry out the following experiments - whether imaginative or real. Decide whether everyday experience confirms the law of conservation of energy.
Residual energy in heat transfer
If the bodies involved in heat transfer are not interacting with other bodies, the amounts of heat given by a hot body and received by a cold body are equal in magnitude.
At this point, the students do not yet know how to calculate the amount of energy needed (or released) to change (or when changing) temperature. None of us is likely to believe that a cup of hot water can heat a lake. However, if you add to a cup of hot water the knowledge that pouring that cup of water into a lake also puts the heat energy in the lake, and that the extra energy always means a temperature rise .... these are the ideas that could be developed here.