Phase changes with entropy?

[Fenared Ortiz 3K]

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.

[Sara Varadharajulu]

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]

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]

So both enthalpy and entropy change during phase changes?

[Lily Sperling 1E]

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]

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

[Guadalupe T 1E]

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.