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The melting of snow on a sunny day

Posted: Tue Mar 12, 2019 3:04 pm
by Hailey Boehm 2H
On test #2 there is a question about the change in Gibbs free energy that would result from the melting of snow on a sunny day. I was able to determine that this process is endothermic, so deltaH is +, and this is a phase change from solid to liquid, so the change in entropy would be +. How can I use this info to determine whether deltaG will be +, -, or 0? thanks!

Re: The melting of snow on a sunny day

Posted: Tue Mar 12, 2019 5:35 pm
by Clarissa Cabil 1I
The melting of snow on a sunny day is actually a spontaneous process (ΔG < 0, negative) because when snow melts, it transforms from a solid to a liquid, which means that the entropy is increasing (ΔS > 0). In real life, snow melts by itself, which is also why ΔG < 0.

Hope this helps!

Re: The melting of snow on a sunny day

Posted: Sat Mar 16, 2019 12:42 pm
by 605168557
Was the reasoning of snow/ice melting on a sunny day being spontaneous the same reason for part c of this problem where the cooling of a hot cup of coffee after it was just brewed was also supposed to be ΔG < 0 ? I was confused because I thought the phase change causing an increase in entropy wouldn't apply to this.

Re: The melting of snow on a sunny day

Posted: Sat Mar 16, 2019 2:34 pm
by Luc Lorain 1L
Just to clarify, how are we able to determine that the value of T(delta)S is greater than that of deltaH, resulting in a negative value? I understand that deltaH= Hfusion of water (=+6.01 kJ/mol) and that both T and delta S are positive... Does the fact that it is a sunny day imply that T is very large?