IB Chemistry - Energetics

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Entropy is one of the most important concepts of thermodynamics. It considers the importance of random behaviour as a driving force behind all physical and chemical change.

This chapter examines disorder in particular systems and how increased disorder leads to greater stability.

Syllabus reference

Reactivity 1.4.1 - Entropy, S, is a measure of the dispersal or distribution of matter and/or energy in a system. (HL)

  • The more ways the energy can be distributed, the higher the entropy. Under the same conditions, the entropy of a gas is greater than that of a liquid, which in turn is greater than that of a solid.
  • Predict whether a physical or chemical change will result in an increase or decrease in entropy of a system
  • Calculate standard entropy changes, ΔS⦵, from standard entropy values, S⦵.


  • Standard entropy values are given in the data booklet.

Tools and links

  • Structure 1.1 - Why is the entropy of a perfect crystal at 0 K predicted to be zero?

In Chapter 4.6