Question

How does the entropy of an isolated system increase?

Answer 1

If the isolated system can not exchange energy or matter with its surroundings and suppose that all the subsystems in a system are at thermal equilibrium, then how does entropy (disorder) come to rise?

Answer 2

Ask @TheSmartOne to help you. (:

Answer 3

Haha, I'm not that great at chemistry.

@aaronq would be the best go-to for chemistry :)

Answer 4

Well I found this: http://physics.stackexchange.com/questions/81095/how-does-the-entropy-of-an-isolated-system-increase

Answer 5

On mobile right now so I might spell some words wrong.

In my chemistry class we defined entropy as the amount of disorder in a system. The most common cause of increases in entropy are usually an increase in temperature. Entropy can also be caused by changing states of matter. If a solid changes to a liquid then entropy increases. Another way to increase entropy is by adding more energy or expanding the system. An increase in kinetic energy also causes an increase in entropy, which of course is in relation to the state of matter which is related to the temperature of the system.

Answer 6

Yes it makes sense that when temperature increases, the number of ways you can arrange particles increases thus disorder, but I am asking about the entropy of an isolated system where neither the exchange of heat nor mass are allowed.

Answer 7

So based on what I have understood from the answers on physics stack exchange is that entropy increases of an isolated system because the particles are in continuous exchange of heat energy because different particles have different amounts of energy.

Answer 8

if you have an isolated system of solid water at 0C, as it melts, its entropy will increase without a change in temperature

Answer 9

What if another substance instead of solid water was placed in an isolated system and assume that the temperature of the system is not close to that required for a phase change to occur.

Answer 10

JFraser, Wouldn't ice melt only if particles absorbed latent heat from the surrounding.If ice was in an isolated system the only way it could melt is by heat exchange between particles but again the kinetic energy of the particles in solid phase is not great enough to overcome the potential energy therefore transforming into liquid phase.

Answer 11

it's an approximation, but it might be possible. You also may have two pure substances that are allowed to mix that would increase entropy, also without the change of thermal energy

Answer 12

In an isolated system work, energy and matter aren't exchanged with the SURROUNDING.
When the system reaches the thermal equilibrium some molecules with high temperature cool down and some molecules with low temperature increase their temperatures. What happens when the temperature increases in the low energy molecules? the internal energy of them are increased , increasing their kinetic energy.

Entropy is the randomness or disorder right? So when the kinetic energy of those molecules increase they move randomly causing disorder or entropy.

This is my view. I might be wrong.
What do u think @Photon336 ?

Answer 13

@Rushwr Can we know the velocity of each particle and therefore classify the molecules as either high energy or low energy molecules. As energy is transferred from the high energy molecules to lower energy molecules, their kinetic energy increases so does entropy. As a consequence of that the high energy molecules lose energy so their entropy must also as well decrease. Why does the overall entropy increase then?

Answer 14

Good question there... @AAbomosalam1998 As i said earlier I am not so sure about these cause I'm still learning all these.
But since we got velocity and their kinetic energy participating here I have one more point to add. Kinetic energy = 1/2 mV^2
There's mass of the molecules taking part in this. IF the masses of low energy molecules which turn in to high energy ones are high then the kinetic energy increases, increasing the entropy. If the initial high energy molecules were light weigh ones, then their kinetic energy would have been less than these right? Hence there will be slight increment in the entropy later when the thermal stability is obtained.

Answer 15

But won't the mass of the particles be equal to one another if the system was made up of a single component.