Question

Entropy is sometimes thought of as mesure of the disorder or randomness present in a system. When we build a bridge or arrange chess pieces in their starting positions on a board, we seem to decrease the randomness of the universe. Why do these situations not violate the second law? What are the entropy changes that occur?

Answer 1

As we now the Second Law of Thermodynamics states that the state of entropy of the entire universe, as an isolated system, will always increase over time. The second law also states that the changes in the entropy in the universe can never be negative.

So, the second law states about the change of entropy of whole universe, but here for given cases like chess board or bridge, we are talking about a particular system not about universe. So for a local system change may be negative. But as a whole for universe the change in entropy will always be positive.