O - Entropy Flashcards Preview

A-level Chemistry > O - Entropy > Flashcards

Flashcards in O - Entropy Deck (24)
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1
Q

What does entropy tell you?

A

How much disorder there is.

2
Q

What is the symbol for entropy?

A

S

3
Q

What is entropy a measure of?

A

The number of ways that particles can be arranged and the number of ways that the energy can be shared out between the particles.

4
Q

When are substances more energetically stable?

A

When there’s more disorder.

5
Q

What are substances ‘more’ when there’s more disorder?

A

More energetically stable.

6
Q

What do particles do to become more energetically stable?

A

The particles move to try to increase the entropy.

7
Q

What factors affect entropy?

A

Physical state, the amount of energy a substance has, and the number of particles.

8
Q

How does physical state affect entropy?

A

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.

9
Q

Which physical state has the highest entropy?

A

Gas.

10
Q

Which physical state has the lowest entropy?

A

Solid.

11
Q

How does the amount of energy a substance has affect entropy?

A

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.

12
Q

What can energy be measured in?

A

Quanta.

13
Q

What are quanta?

A

Fixed ‘packages’ of energy.

14
Q

How does the number of particles affect entropy?

A

More particles means more entropy.

The more particles you have, the more ways they and their energy can be arranged.

15
Q

Increasing disorder…

A

…increases entropy.

16
Q

Decreasing disorder…

A

…decreases entropy.

17
Q

What is the entropy change of the system?

A

The entropy change between the reactants and products.

18
Q

What is the total entropy change?

A

The sum of the entropy changes of the system and the surroundings.

19
Q

What is the entropy change of the surroundings?

A

The entropy change between the system and the surroundings.

Because energy is transferred to or from the system.

20
Q

Reactions with what value of total entropy change are more likely to happen spontaneously?

A

Reactions with a positive value of total entropy change.

21
Q

What does the total entropy change have to be for a reaction to happen spontaneously?

A

Positive (or zero).

22
Q

What is a feasible reaction?

A

One that, once started, will carry on to completion, without any energy being supplied to it.

23
Q

For a reaction to be feasible what must the total entropy change be?

A

Positive or zero.

24
Q

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?

A

Positive and at least as large as the entropy change of the system.