Difference Between Hot Body And Cold Body
Though all know that heat is energy, the conception as to the nature of heat is general. Just what happens to a body when it becomes hotter or colder ? Most people are content in saying that the body gains heat or loses it.
Bodies are made up of very small particles called molecules. For all temperatures we are able to produce these molecules which are found to be in a state of very rapid motion. If a piece of iron is heated, we see that it expands but no weight is added to it. How, then, can it possibly get larger? The conception is that the molecules are made to go faster than before, consequently striking one another with greater force and shoving outermost molecules away; so, finally, all of them are at greater distances apart and the body is measurably larger. This can be proved for, although we cannot see the spaces between the molecules, we can force certain gases through a hot body that will not go through the cold body. If, when a body becomes hot, the molecules go faster, and that is the only change we can see, we are justified in concluding that heat is nothing but the energy of a moving molecule ; in other words, simple mechanical energy of the molecule. Just as can turn a wheel by means of mechanical energy, we can make a body hot by means of molecular mechanical energy.
When a body absolutely cold then the molecules are not moving at all. This state of affaire takes place at what is known as absolute zero of temperature, which is 273 deg. below zero Centigrade, or 459 deg. below zero Fahrenheit. Nothing can get colder than this temperature, for coldness is simply an absence of heat. Heat is merely the energy of a moving molecule.