The new way of teaching energy is keen to point out that in every energy transfer some energy follows the pathway of heating by particles or heating by radiation to increase the thermal energy store in the surroundings. It concerns me that classes will touch the walls and point out that they don't feel any warmer. So here's the experiment I use to open this can of worms. Two beakers with 150 ml of boiling water in each. One stands in a washing up bowl half full of cold water; the other stands in a smaller plastic tub half full of cold water. Temperatures of hot and cold water in each pair are recorded every minute and graphs are plotted. There is an energy transfer from the hot water to the cold water in each case. The cold water in the small tub gets warmer by a few degrees if correctly stirred and the cold water in the big tub stays almost exactly the same despite having clearly been in receipt of energy that should fill its thermal store. So why doesn't the temperature go up? It's because thermal energy makes atoms vibrate. Temperature is effectively a measure of atom vibration. It's called internal energy and is a little more complicated than this but you get the idea) In the big tub, far more atoms are in receipt of what should be the same amount of energy so each gets a much smaller share. The atoms wobble a tiny bit more but not enough to register on our thermometers. And that is what is going on when energy transfers use a heating pathway to transfer energy to the surroundings. We say that the energy has been wasted - a human value judgement - because we can't make any use of it. We call this loss of usefulness "
dissipation".
