The first aspect of entropy is concerned with the second law of thermodynamics . This law has been stated in various forms, but it can be summarized by saying that nothing ever works with perfect efficiency. Any engine, motor or other system which converts energy from one form to another will not convert 100 per cent of the energy. Some will be lost by friction, or heat loss, or other forms of wastage. The entropy change of such a system is defined as being equal to the energy change divided by the temperature of the system.
All systems attempt to maximize their entropy.
On a microscopic scale, entropy is a measure of the number of ways that a system can arrange itself. To see why entropy tends towards a maximum, consider several particles in a box. We can arrange them so that they are all in a corner, or more evenly distributed around the box. There are far more ways to arrange them so that they are evenly distributed. The entropy of the disordered, evenly distributed arrangement is much higher than an orderly bunching of particles in a corner, thus the system finds the state of highest entropy.