O - Entropy Flashcards
What does entropy tell you?
How much disorder there is.
What is the symbol for entropy?
S
What is entropy 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.
When are substances more energetically stable?
When there’s more disorder.
What are substances ‘more’ when there’s more disorder?
More energetically stable.
What do particles do to become more energetically stable?
The particles move to try to increase the entropy.
What factors affect entropy?
Physical state, the amount of energy a substance has, and the number of particles.
How does physical state affect entropy?
Solid particles just wobble about in a fixed point - there’s hardly any disorder, so they have the lowest entropy.
Gas particles whizz around wherever they like. They’ve got the most disordered arrangements of particles, so they have the highest entropy.
Which physical state has the highest entropy?
Gas.
Which physical state has the lowest entropy?
Solid.
How does the amount of energy a substance has affect entropy?
Energy can be measured in quanta - these are fixed ‘packages’ of energy. The more energy quanta a substance has, the more ways they can be arranged and the greater the entropy.
What can energy be measured in?
Quanta.
What are quanta?
Fixed ‘packages’ of energy.
How does the number of particles affect entropy?
More particles means more entropy.
The more particles you have, the more ways they and their energy can be arranged.
Increasing disorder…
…increases entropy.
Decreasing disorder…
…decreases entropy.
What is the entropy change of the system?
The entropy change between the reactants and products.
What is the total entropy change?
The sum of the entropy changes of the system and the surroundings.
What is the entropy change of the surroundings?
The entropy change between the system and the surroundings.
Because energy is transferred to or from the system.
Reactions with what value of total entropy change are more likely to happen spontaneously?
Reactions with a positive value of total entropy change.
What does the total entropy change have to be for a reaction to happen spontaneously?
Positive (or zero).
What is a feasible reaction?
One that, once started, will carry on to completion, without any energy being supplied to it.
For a reaction to be feasible what must the total entropy change be?
Positive or zero.
If the entropy change in the system is negative, what must the entropy change in the surroundings be for the reaction to still be feasible?
Positive and at least as large as the entropy change of the system.
