Entropy (S) is a measure of the disorder or randomness in a system. It tells us how spread out or dispersed the energy and particles are in a system.
Key points:
- Higher entropy means more disorder or more ways for the particles to arrange themselves.
- Example: Gas molecules moving freely in a room have higher entropy than the same molecules in a solid.
- Lower entropy means more order or fewer ways to arrange particles.
- Example: A crystal lattice has very low entropy because its particles are fixed in an orderly structure.
- Change in entropy (ΔS):
- If ΔS > 0, disorder increases.
- If ΔS < 0, disorder decreases.
- Significance in reactions:
- Reactions that increase entropy are often more likely to be spontaneous.
- Entropy is a key factor in determining the Gibbs free energy and spontaneity of a reaction.
Simple analogy:
- Think of a messy room versus a tidy room. A messy room has high entropy (disorder), while a tidy room has low entropy (order).