Entropy Flashcards
Define entropy
Entropy, S, is a measure of the number of ways that particles can be arranged and the number of ways that the energy can be shared out between the particles
What gives a high value of entropy?
The more disordered the particles are, the higher the entropy is. A large, positive value of entropy shows a high level of disorder
What two things affect entropy?
- Physical state
2. Amount of particles
How does physical state affect entropy?
Solid particles vibrate around a fixed point - there’s hardly any disorder, so they have the lowest entropy. Gas particles have the most disordered arrangement of particles, so they have the highest entropy
How does amount of particles affect entropy?
More particles means more entropy. The more particles you have, the more ways they and their energy can be arranged - entropy increases when the number of moles increases
Why do substances tend towards disorder
Substances are more energetically stable when there’s more disorder, so particles will move to increase their entropy. This is why some reactions are feasible even when the enthalpy change is endothermic
What is the equation to calculate entropy change
Entropy change = Sproducts - Sreactants
This is just the difference between the entropies of the products and reactants
How do you find Sproducts and Sreactants?
You can find these by adding up all the standard entropy of the products, and by adding up all the standard entropy of all the reactants
Define standard entropy of a substance
Standard entropy of a substance is the entropy of 1 mole of that substance under standard conditions (pressure of 100kPa and temperature of 298K)
Does an increase in entropy mean that it is feasible for a reaction to occur?
A total increase in entropy means that it is feasible for a reaction to occur, but it is not a guarantee that it will - enthalpy, temperature and kinetics all play a part in whether or not a reaction occurs
