الحرارة .. الفيزياء

Heat .. Physics

Heat

The confusion between the concepts of heat and temperature remained until the eighteenth century, and Joseph Black (1728 - 1799) was the first to distinguish between these two concepts until it became known today with great accuracy according to the atomic and molecular theory of matter.

This is because the temperature of a body is a measure of the average energy of its atoms and molecules, while heat itself is a measure of its total energy, and for this reason temperature is not subject to the amount of matter, unlike heat itself, which is closely related to matter. Everyone knows that a glowing spark from a millstone cannot burn human skin if it falls on it because it contains only a small amount of mass, in contrast, an iceberg can generate a large amount of heat due to its enormous mass.

When we heat a certain body, its atoms and molecules gain kinetic energy that raises its temperature. All types of matter behave in the same way, some of them rise. And its temperature is not more than others for the same amount of heat. Given to it, each substance is characterized by its heat capacity - that is, the amount of heat needed to raise its temperature by one degree Celsius. As for the specific heat capacity, it is the amount of heat needed to raise the temperature of one kilogram of the substance by one degree Celsius and is symbolized by the letter N. Accordingly, the amount of heat 5 needed to raise the temperature of the mass K is the amount of D degrees Celsius 5 = K N D. Heat is transferred from one place to another in three different ways: thermal conduction, thermal convection, and radiation. Thermal conduction occurs when two solid, liquid, or gaseous bodies come into contact with each other, so kinetic energy is transferred from the atoms and molecules of one to the atoms and molecules of the other. Thermal convection occurs in both liquids and gases, and it is the passage of heat currents that are formed as a result of the difference in the temperature of the body generated by the difference in the value of its density. As for radiation, it occurs between two masses separated only by empty space.