WHAT IS ACTUALLY "HEAT"?

Automobile engines, ovens, chemical reactions work due to heat. How to see , feel and understand the heat?

We know all the substances are made up of molecules. When the molecules are in motion(moving, vibrating, rotating etc.,) the substance is said to carry heat energy.

Take a hot tea in a cup and put a cold spoon in it. We know the spoon will be heated up. What happens? The molecules are in fast random motion in the hot tea. These molecules collide with the molecules of the spoon and set them in vibration. Now we say heat is transfered from tea to spoon.

As a speed of the molecules increases(kinetic energy), the heat content of the substance increases and we say the temperature increases.

Even at freezing point (at 0 degree c), the molecules really do not freeze but move at low speeds. When all the molecules come to stand still, we say the temperature is absolute zero or 0 degree kelvin. At 0 degree k: no movement , no heat, no temperature.

We know radiation or waves also cause heat. The radiation behaves like particles called photons. The movement of photon causes heat. In a microwave oven, the photons collide with water molecules in the food and the food is warmed up.

Imagine two balls. one is fast moving and other is slow moving. When the fast one hit the slow ball, the energy is transfered from first to the latter. The slow ball gains energy due to impact and moves fast. The fast ball slows down due to loss of energy. There is a high probability of transferring energy from fast ball to slow ball and not vice versa.

It is the same case in heat energy also. That is why the thermodynamic laws says it is impossible to transfer heat from a body of low temperature to a body of high temperature.

Heat passage also indicates time passage. As a time flows, heat also flows. So temperature is also a measure of time.

Next time, when you feel the hot water, remember that the fast moving water molecules dash against your skin with vengeance.

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