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entropy of vaporization of water

Posted: Mon Feb 12, 2018 10:13 am
by Belle Calforda3f
I understand how to do a problem that asks for the entropy of vaporization of water at room temp, yet I do not really get how water has an entropy of vaporization for room temp. Is water vaporizing at room temp. even if it is not physically boiling?

Re: entropy of vaporization of water  [ENDORSED]

Posted: Mon Feb 12, 2018 10:18 am
by Sara Varadharajulu
at room temperature, water does have a entropy of vaporization---its like how a puddle evaporates---no one is boiling the puddle but eventually it becomes vapor.
to solve these problems you usually 1) calculate entropy change for raising the temp to boiling point 2) calculate entropy of vaporization (usually from enthalpy of vaporization 3) calculate the entropy change when you bring the water back down to room temp. since entropy is a state function, you can break up the steps.

Re: entropy of vaporization of water

Posted: Mon Feb 12, 2018 11:09 pm
by Dang Lam
to elaborate on that, given that enthalpy is a state function, we don't care about the path taken. Regardless, we will get the same answer if we take the final state - initial state. Therefore, this idea allows us to calculate enthalpy of h2o vaporization through multiple steps.

Re: entropy of vaporization of water

Posted: Sun Feb 10, 2019 9:28 pm
by annabel 2A
Does that mean that water/substances can undergo phase change without input of heat?