Differences in Heat Capacity

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Gabriel Ordonez 2K
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Joined: Sat Jul 20, 2019 12:15 am

Differences in Heat Capacity

Postby Gabriel Ordonez 2K » Thu Feb 13, 2020 3:05 pm

What are the different types of heat capacities we should take into account for this class?

Ally Huang- 1F
Posts: 103
Joined: Thu Jul 25, 2019 12:16 am

Re: Differences in Heat Capacity

Postby Ally Huang- 1F » Thu Feb 13, 2020 3:08 pm

Heat capacity is the heat required to raise the temperature of an object by 1 degrees celsius. Specific heat capacity is the heat required to raise temperature of 1 gram of a substance by 1 degrees celsius. Molar heat capacity is the heat required to raise the temperature of one mole of a substance by 1 degrees celsius. Gasses have a molar heat capacity specific for a gas at a constant volume and a constant pressure.

Mulin_Li_2J
Posts: 105
Joined: Sat Aug 17, 2019 12:16 am

Re: Differences in Heat Capacity

Postby Mulin_Li_2J » Fri Feb 14, 2020 11:19 am

Another two heat capacity you might want to understand is Cv,m, molar heat capacity of gas under constant volume, and Cp,m, molar heat capacity of gas under constant pressure. Using C = q/T and q(constant pressure) = ΔH and ΔH = ΔU + PV, we can derive the equation that Cp,m = Cv,m + R. Then based on equipartition theorem, we can deduce that Cv,m = (3/2)*R for monoatomic gas, thus Cp,m = (5/2)*R. There is a table somewhere in the textbook with Cv,m and Cp,m for momatomic, linear, and non-linear gas respectively.

Hope this can help!!! -_+

JasonLiu_2J
Posts: 109
Joined: Sat Aug 24, 2019 12:17 am

Re: Differences in Heat Capacity

Postby JasonLiu_2J » Fri Feb 14, 2020 12:26 pm

It might also be good to know that the heat capacity for a substance is an extensive property, as it depends on how much of the substance is present. Specific heat capacity (energy required to heat a gram by 1 degrees C) and molar heat capacity (energy required to heat a mol by 1 degrees C), are intensive properties which are constant values for specific substances. Monatomic ideal gases have a special molar heat capacity that you can calculate by using 3/2R under constant volume and 5/2R under constant pressure. This of course indicates that all monatomic ideal gases have the same molar heat capacity under constant volume or constant pressure. Hope this helps!

Aiden Metzner 2C
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Joined: Wed Sep 18, 2019 12:21 am

Re: Differences in Heat Capacity

Postby Aiden Metzner 2C » Wed Feb 19, 2020 1:17 pm

We need to know heat capacity for calorimeters, which is just the heat capacity required to raise a substance 1 degree celcius. But also specific and molar heat capacities are important to know. Specific being the amount of heat required to raise 1 gram of a substance 1 degree celcius, and molar being the amount of heat required to raise a mole of a substance 1 degree celcius


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