## Phase changes with entropy?

Fenared Ortiz 3K
Posts: 37
Joined: Wed Nov 16, 2016 3:03 am

### Phase changes with entropy?

Do we still have to account for phase changes when trying to find the entropy of the system? If so how would we approach doing so.

Posts: 60
Joined: Thu Jul 13, 2017 3:00 am
Been upvoted: 1 time

### Re: Phase changes with entropy?

yes, you do. the entropy increases when going from solid to liquid to gas and decreases in the opposite direction. you can use delta s= q(rev)/T. the q for a reversible reaction is equal to the enthalpy of fusion, vaporization etc. this will help you account for the entropy change during phase changes.

Sally Nason - 1K
Posts: 40
Joined: Fri Sep 29, 2017 7:05 am

### Re: Phase changes with entropy?

During a phase change, the temperature does not change but heat must still go into/leave the system in order to cause the phase change. Since heat is entering or leaving the system, the entropy will change and therefore needs to be accounted for.

JennyCKim1J
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

### Re: Phase changes with entropy?

So both enthalpy and entropy change during phase changes?

Lily Sperling 1E
Posts: 49
Joined: Tue Oct 10, 2017 7:14 am

### Re: Phase changes with entropy?

Yes, both enthalpy and entropy change during a phase change, but keep in mind when simply asked is the reaction spontaneous at a given temp, you do not account for entropy or enthalpy change to get to that temp, but are only looking at the spontaneity of the phase change itself.

CalebBurns3L
Posts: 47
Joined: Fri Sep 29, 2017 7:07 am

### Re: Phase changes with entropy?

Both the entropy and enthalpy change during a phase change, so yes.

Posts: 58
Joined: Fri Sep 29, 2017 7:04 am

### Re: Phase changes with entropy?

You can also use the equation deltaS= n x delta H / T when there is vaporization/ fusion and deltaS= nCpln(T2/T1) for phase changes.

### Who is online

Users browsing this forum: No registered users and 2 guests