## Internal Energy

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Kyra Dingle 1B
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Joined: Fri Sep 29, 2017 7:04 am

### Internal Energy

What is the difference between internal energy and enthalpy?

Sabrina Dunbar 1I
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### Re: Internal Energy

Enthalpy is the amount of heat released or absorbed at constant pressure and it is written as H. When this H is changed between the products and the reactants in a chemical equation it becomes ∆H, meaning it is the change in enthalpy. This differs from the internal energy of the system greatly. The internal energy of a system is the sum of the work done on the system as well as the heat present in the system. The amount of heat gained or released by a substance at constant pressure (qp) is the same as ∆H, again meaning the change in enthalpy. This is how these two values, enthalpy and internal energy relate. ∆U=qp+w

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### Re: Internal Energy

Internal energy is the energy of the whole system work + enthalpy. While enthaply is just heat released or absorbed, a part of internal energy.

Katie Lam 1B
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Joined: Fri Sep 29, 2017 7:06 am

### Re: Internal Energy

However, when no expansion work is done, the change in internal energy is equal to the change in enthalpy.

Yutian Zhao -1J
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Joined: Fri Sep 29, 2017 7:05 am

### Re: Internal Energy

According to U=q+w, under constant pressure (deltaH=q),U=delta H+w. With that being said, the internal energy equals sum of enthalpy change and the work done by/on the system.