It's not literally "hot" in and of itself!  In since 1843, when Joule discovered the relation between calories and energy. He (basically) worked out that 1 calorie is the same as 4.2 joules (kek). So "heat-energy" is just energy. Philip Goglia has been living under a rock for a couple of centuries. BTW, 1 calorie is the energy required to heat up 1 gram of water by 1 deg C. Or did you mean food calories (kcal, in which case you are right)?