Entropy of Fusion

[MedPR]

So the entropy of fusion is always positive because liquid has greater entropy than solid. You could go one step further and say that in most cases positive entropy is associated with phase changes to phases of lower density, since liquids are typically more volumous than solids and therefore have a lower density.

However, in the case of water, positive entropy is actually associated with a phase change to a phase of greater density since liquid water is more dense than solid water.

👍?

Going to edit this since it has created some confusion about the direction I wanted this to go 🙂

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[milski]

Kind of, sort of. Entropy of fusion is the entropy for transition from solid to liquid phase. It is positive, because a liquid has higher entropy than the solid (in general). Same thing applies for entropy of vaporization - more entropy in gaseous form, so it is also positive.

Entropy is associated with how "ordered" the molecules of a substance are. Typically having them better ordered allows to push them closer together and that gives higher density of the substance when in a state with a lower entropy.

Water is a bit of an exception since ice does have more ordered placement of its molecules but that results in a bit of extra spacing between them which makes it slightly less dense than liquid water.

 

[gettheleadout]

So the entropy of fusion is always positive because liquid has greater entropy than gas. You could go one step further and say that in most cases positive entropy is associated with phase changes to phases of lower density, since liquids are typically more volumous than solids.

However, in the case of water, positive entropy is actually associated with a phase change to a phase of greater density since liquid water is more dense than solid water.

👍?

Milksi answered nicely but this is backwards, MedPR.

 

[pfaction]

Wait, what is going on? Fusion is melting, from solid to liquid...it has higher entropy because solids are the most organized and liquids are less organized. Gases are the most entropy phase, so going from G->L is a negative entropy.

So are we saying here that solid entropy here is more or less in water than liquid? I thought it was solid < liquid entropy.

 

[MedPR]

Kind of, sort of. Entropy of fusion is the entropy for transition from solid to liquid phase. It is positive, because a liquid has higher entropy than the solid (in general). Same thing applies for entropy of vaporization - more entropy in gaseous form, so it is also positive.

Entropy is associated with how "ordered" the molecules of a substance are. Typically having them better ordered allows to push them closer together and that gives higher density of the substance when in a state with a lower entropy.

Water is a bit of an exception since ice does have more ordered placement of its molecules but that results in a bit of extra spacing between them which makes it slightly less dense than liquid water.

Milksi answered nicely but this is backwards, MedPR.

Yea, just noticed that I typed "gas" instead of "solid"... Not sure what I was thinking. Does what I wrote make more sense if you substitute solid for gas in that first sentence?

 

[aspiringdoc09]

Yea, just noticed that I typed "gas" instead of "solid"... Not sure what I was thinking. Does what I wrote make more sense if you substitute solid for gas in that first sentence?

Order of decreasing entropy: gases > liquids > solids

 

[deleted357625]

Order of decreasing entropy: gases > liquids > solids

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Entropy: Phase changes, change in moles, complexity