Second+Law


 * Second Law of Thermodyanmics**

Any time energy undergoes a //spontaneous// transformation or energy transfer, the //disorder// of the universe (the system and its surroundings) must increase.

This law introduces two concepts: disorder (referred to as entropy, S) and spontaneity (referred to as Gibbs Free Energy, G).


 * Entropy** is a measure of disorder. The more chaotic a system becomes, the greater its entropy value will be. Think of the card game solitaire. As you play, you are arranging the deck of cards into order. This is a negative change in entropy (-dS). If, when you finish the game, you shuffle the deck, you introduce disorder, which is a positive change in entropy (+dS).


 * Gibbs Free Energy** is a measure of spontaneity. If a process or energy transfer occurs without any outside influence, it is spontaneous, which is a negative change in Gibbs Free Energy (-dG). If the process or energy transfer requires help, it is nonspontaneous, and carries a positive change in Gibbs Free Energy (+dG).

Therefore, the two concepts - entropy and spontaneity - are linked in the Second Law. Think about the card game - it takes work from you to organize the deck during solitaire, and is thus a -dS and a +dG process. Shuffling the deck is an interesting concept in thermodynamics: it is a +dS and a +dG (increasing disorder but not spontaneous).