The Laws of Thermodynamics
The law of the conservation of energy is supplemented by a second equally comprehensive law, and one which is more fundamental in its meaning than the first. It is generally known as the second law of thermodynamics, but is sometimes called the law of entropy. The first law tells us about the amount of the exchange which occurs when one form of energy is converted into another, but as to whether the exchange can occur or under what circumstances it does occur the first law says nothing. It merely states that the energy which has disappeared in any process is equal in amount to the new form of energy which is produced by it. The second law now teaches something more, for it indicates the ease or difficulty which attends the conversion of one form of energy into another. The second law of thermodynamics states that positive process can occur spontaneously.