heat capacity

[chiddler]

I'm trying to understand the relationship between heat capacity and enthalpy of vaporization/fusion.

Can heat capacity tell us anything about ΔHfusion? For example, if we have one substance with C(solid)=0.1, and another with C(solid)=10, can I say that it takes more heat to convert the second to liquid?

Why?

I'm thinking that C is just the amount it takes to raise the temperature. ΔH is just the amount to convert phases. But this feels incorrect.

thank you.

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[milski]

I'm trying to understand the relationship between heat capacity and enthalpy of vaporization/fusion.

Can heat capacity tell us anything about ΔHfusion? For example, if we have one substance with C(solid)=0.1, and another with C(solid)=10, can I say that it takes more heat to convert the second to liquid?

Why?

I'm thinking that C is just the amount it takes to raise the temperature. ΔH is just the amount to convert phases. But this feels incorrect.

thank you.

In general, you cannot infer one from the other. Without going in details, heat capacity depends a lot more on the structure of the molecules of the substance while the heat of fusion will depend mostly on how much molecules of that substance attract each other.

You can think about heat capacity as a way to describe how much energy you can store in a molecule and heat of fusion how hard is to pull molecules from each other. You can have a nice, 'springy' molecule which stores a lot of energy but still interacts very little with its neighbors and is easy to melt.

 

[chiddler]

very good. i'm satisfied with your answer.

thanks.