delta U for an ideal gas expansion


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Elizabeth Bowen 1J
Posts: 53
Joined: Wed Nov 14, 2018 12:20 am

delta U for an ideal gas expansion

Postby Elizabeth Bowen 1J » Tue Feb 11, 2020 4:39 pm

can anyone explain why delta U=0 for an isothermal ideal gas expansion/compression?
thanks

AArmellini_1I
Posts: 107
Joined: Fri Aug 09, 2019 12:15 am

Re: delta U for an ideal gas expansion

Postby AArmellini_1I » Tue Feb 11, 2020 4:51 pm

Because isothermal means energy/heat and matter cannot leave or enter the system, therefore the internal energy of the system (delta U) is constant

Elizabeth Bowen 1J
Posts: 53
Joined: Wed Nov 14, 2018 12:20 am

Re: delta U for an ideal gas expansion

Postby Elizabeth Bowen 1J » Tue Feb 11, 2020 5:02 pm

Thanks, if we were told that a gas expansion is isothermal, do you think that we should assume it's an ideal gas if not specified (so that we can use the fact that delta U=0)?

AArmellini_1I
Posts: 107
Joined: Fri Aug 09, 2019 12:15 am

Re: delta U for an ideal gas expansion

Postby AArmellini_1I » Tue Feb 11, 2020 5:09 pm

Elizabeth Bowen 1J wrote:Thanks, if we were told that a gas expansion is isothermal, do you think that we should assume it's an ideal gas if not specified (so that we can use the fact that delta U=0)?

Yeah I believe so! But I don't think whether or not it is an ideal gas influences delta U = 0. I'm pretty sure that statement is true for all isothermal systems.


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