## Quiz One - #5 Calculating Heat

$\Delta U=q+w$

104781135
Posts: 13
Joined: Wed Sep 21, 2016 2:56 pm

### Quiz One - #5 Calculating Heat

Hello! Can anybody explain how to do #5 on our first quiz? I knew the equations to use, I think I just didn't use the right heat capacities. How do I know which ones to use?

Hannah_El-Sabrout_2K
Posts: 20
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Quiz One - #5 Calculating Heat

The quizzes vary from day to day, so I would ask your TA or someone in your discussion.

Alyssa Chan 3B
Posts: 16
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Quiz One - #5 Calculating Heat

I think we have the same quiz--melting a -55˚C block of ice into 25˚C water?

When you first melt ice from -55˚to 0˚, you use the specific heat capacity of ice in the equation q = mc∆T. During the phase change from ice to water (at 0˚), you use the heat of fusion in the equation q = n∆Hfus (note that ∆Hfus is in kJ/mol). From 0˚ water to 25˚ water, you use the specific heat capacity of water in the equation q = mc∆T.

Hope this helps!