Dat destroyer chem question

[niv3k]

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Okay so I was reading the last paragraph or so on the page. It stated that entropy is greater in gasses > liquids > solids.

They also said that entropy is greater in C4H10 than in C3H8. I read somewhere that carbon straight chains between 1-4 carbons are gasses, 5-16 or so are liquids, and anything greater than 16 carbon atoms in a straight chain are waxes or solids.

If that is the case, why is entropy greater in the C4 molecule than in a C3??

 

[ilovefruits]

Oh I remember I was super confused about this too! And then I read somewhere on this forum I think (but super old thread) that told me, since there are more single bonds in that C4 molecule, and you can rotate all the single bonds, so you can create more chaos within the molecule! But like, a solution of C3 would def have more entropy than a solution of C4.

 

[haiKUHN]

We always think entropy in terms of "chaos and disorder" but really entropy has to do with the amount of energetically equivalent spatial arrangements possible for a specific molecule. The greater arrangements available, the higher the entropy. With the ability to move more freely, gas molecules will have more entropy because they are free to rearrange. Solid molecules don't have the freedom to move thus can't rearrange.

With more carbon atoms and thus more hydrogen molecules, there are more arrangements available.

 

[niv3k]

Ahh okay I get it thanks.