# Entropy (disorder)

1. Aug 27, 2006

### quantumlight

i got this question in my chem review worksheet

State if the following increases or decreases the disorder of a system?

1) sublimation of dry ice
2) freezing of water
3) increasing pressure over Nitrogen gas that is above water

i put

1) increase
2) decrease
3) increase

2. Aug 27, 2006

### Andrew Mason

I am not sure what is meant by "disorder". Are you taking this to be synonymous with "entropy"?

It is a little unclear what the system is in these three examples. If the system includes the environment in which these things occur, then the answer is that Entropy increases in all three. For example, the freezing of water can occur in a freezer in which heat is pumped out of the water and into a hot reservoir. If the system includes the hot reservoir, entropy increases.

AM

3. Aug 27, 2006

### Gelsamel Epsilon

According to what I understand is the definition entropy all 3 of your answers are right, but I never actually studied entropy in chemistry (no thermodynamics for me :( ). So don't be supprised If I'm wrong and hence you're wrong.

Edit:

The entropy of the whole system there would increase, but the entropy of the ice itself (which I think is what is being asked) would decrease.

(Again this is just from what I understand the definition of entropy is, so if I'm wrong could you please explain if I'm wrong).

Last edited: Aug 27, 2006
4. Aug 28, 2006

### quantumlight

right now the chapter im doing is "solutions, colloids and solubility of different substances" its talking about how some solutions that doesnt hav much of an energy difference still spontaneously dissociate and that is cuz of the disorder that accompanies such an action

5. Aug 30, 2006

### NotMrX

If we assume that the system is just what is mentioned...ie sublimation of dry ice or freezing of water, then it is probably easiest to look at entropy the macroscopic way. The statatiscal microscopic way is the way where the disorder phrase makes more sense ussually.

All you have to do look at whether heat is being released or taken in.
1)Sublimation of dry ice takes in heat so its entropy increases.
2) Water when it freezes gives off heat, so entropy decreases.
3) When the pressure is increased we assume it adiabatic so no heat is added. Also $$N_2$$ is hardly soluble. However, the change in entropy is a statefunction. You can look at the process as two steps, isothermal compression, then adding heat. The key word is adding so yes it increases.

6. Aug 31, 2006

### quantumlight

thnx why is there an at least 10 letter limit?

7. Aug 31, 2006

### Gelsamel Epsilon

So people can't spam or something, I guess.