Ideal gas expansion


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Jane Burgan 1C
Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

Ideal gas expansion

Postby Jane Burgan 1C » Thu Feb 07, 2019 10:51 am

Why is the internal energy of an ideal gas equal to 0 when it expands isothermally and reversibly?

Courtney Quan 1C
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am
Been upvoted: 2 times

Re: Ideal gas expansion

Postby Courtney Quan 1C » Thu Feb 07, 2019 11:10 am

When an ideal gas isothermally expands or is compressed, it does so at the same (constant) temperature. Since there is no change in temperature, the gas molecules will continue to move at the same speed and there is no energy change, which is why the internal energy change delta U is equal to zero.

Celine Hoh 2L
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

Re: Ideal gas expansion

Postby Celine Hoh 2L » Thu Feb 07, 2019 11:36 am

I understand that q=0 as there is no net heat change. But why isn’t W a negative value as the system has done work to expand?

Carine Tamamian 2B
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

Re: Ideal gas expansion

Postby Carine Tamamian 2B » Thu Feb 07, 2019 12:04 pm

Maybe because the work energy itself is still an amount, disregarding the fact that it's lost or gained. But I'm not sure though, can someone explain?

Karan Thaker 2L
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

Re: Ideal gas expansion

Postby Karan Thaker 2L » Thu Feb 07, 2019 12:56 pm

I think you're right... the work energy is thought of a value, rather than being gained or loss in this context.


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