Isothermal Process


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Shannon Wasley 2J
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Isothermal Process

Postby Shannon Wasley 2J » Tue Feb 13, 2018 2:40 pm

If in an isothermal process there is no change in temperature, why wouldn't the value of q be 0, since the equation is q = mCdeltaT. Why isn't this delta T equal to 0 due to the fact that the process is isothermal?

Tim Foster 2A
Posts: 73
Joined: Fri Sep 29, 2017 7:07 am

Re: Isothermal Process

Postby Tim Foster 2A » Tue Feb 13, 2018 2:55 pm

The equation q=mCdeltaT is somewhat useless for isothermal processes because it has to do specifically with heat capacities. It's not that a substance that doesn't change in temperature has no heat capacity at all, its just that its impossible to tell what that heat capacity is when the temperature doesn't change. Even if you know the heat capacity of this substance through the dreaded Appendix 2A or some other kind of chemistry textbook tom-foolery, q=mCdeltaT isn't going to help you very much rn Shaknown. Instead, think back to the properties of isothermal processes for ideal gases. When an ideal gas expands isothermally, the change in Internal energy is equal to 0. This in turn means that 0=q+w and q=-w. As Lavelle would say- Aha! To find the work done by a gas at a constant pressure, we can use the simple equation w=-P(ex) \Delta V
Hereby, q is simply equal to the opposite of the value we compute for work.
It also helps remember that heat and temperature are not the same thing. You can heat a gas without its temperature increasing so long as the volume(or other quality of ideal gases) increases(or decreases) to counteract this increase in heat energy and keep temperature constant. Hope this helped! Have a great day!

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