delta U when volume is constant

[OishiBhattacharya2K]

I am a little confused as to why delta U = qv if the volume in constant, if somebody could clarify that would be great!

[Sujin Lim 1H]

deltaU = qv when the volume is constant because it means that the volume can not change. If the volume can not change, then there can be no work of expansion, so w=0. Then the equation deltaU = q+w just turns into deltaU = qv, where qv is the heat transfer of a system under constant volume. Hope this helps!

[Rose Arcallana 2B]

So we have the normal equation: delta U = Q + Won, when the system is at constant volume, Won = 0 because there is no energy being used to change the volume of the system (W = -Pex * delta V). Hope it helps!

[Akane Shimoyoshi 3F]

When volume is constant, delta V = 0. Since delta U can be found using the equation: delta U = q + w, and work is -p(deltaV), you find that work = 0 when volume is constant. Plugging that back into the delta U equation gives you delta U = q.

[A 3F]

ΔU = q + w, where w = -PΔV, so ΔU = q - PΔV. When the volume is constant, there is no change in the volume so ΔV = 0. When you plug this back into the equation, the work term (-PΔV) becomes 0 so ΔU = q.

[Alyssa Ly 2G]

Hello!

The reason why delta U = q when the volume is constant is because when the volume is constant, no work is being done, thus, w = 0. Since delta U = q + w, delta U = q + 0 = q.

Looking at the equation for work, w = -P(delta V), delta V would equal to 0 when the volume is constant since the volume is NOT changing. Thus, w = -P(0) = 0 --> w = 0.

Hope this helps! :))

[Joellen 1B]

When volume is constant, no work is being done, therefore delta U = q+0 or delta U = q

[Phoebe Ko 3E]

The entirety of the equation should be ∆U = q + w. When the volume is constant in a reaction though, there is no work done, or no energy transferred by compression. Therefore, we can disregard the "w" in the equation and derive ∆U = qv, where qv is the energy transferred by heating under constant volume. I hope this was helpful!