Question: what makes hot water, hot?

Kevin Motherway answered on 18 Nov 2014:

When we say something is hot its a measure of the level of energy the molecules are are at. Water at low energy is a solid (ice) at higher energy it is liquid and at very high energy state is a gas (steam). Even when water is not a boiling point some of the molecules get heated up or given energy from the friction of molecules of air and get up to a high enough energy level to turn to gas (evaporation). So when you feel the sensation of heat from water you’re actually feeling the sensation of heat energy in the water transferring to your body and exciting the molecules in your hand. When water feels cold its at a lower temp than your hand and you’re feeling the sensation of loosing heat energy to the water as your hand heats the water up and excites the molecules in the water. Heat is all about energy and feeling something is hot or cold is all about energy transfer!