Isothermal and reversible

[Julia Kim 1D]

What exactly does this mean?

Also, in def it says isothermal is deltaT is 0. So wouldn't that make q=0? But in problems, it says that deltaU=0. Why?

[Maggie Zhang 1A]

Hi! Isothermal means that temperature is constant, therefore the change in temperature is zero. Change in internal energy is dependent on change in temperature, thus the change in internal energy is zero in isothermal conditions. Q is heat, rather than temperature, and even in isothermal conditions, work and heat are still being done, but are equal counterparts to each other as their sum equals zero (since q+w=delta U). Q is only equal to zero in adiabatic conditions, when a gas's temperature and pressure change with no gain or loss of heat. Hope this helped!

[Alex Chiodo Ortiz 3G]

So for an isothermal reaction you would still use U=q+w because q still exists? But doesn't q=nCdeltaT, and isn't deltaT 0 in isothermal, so wouldn't it be U=w?

[Cristian Yanes 1L]

So for an isothermal reaction you would still use U=q+w because q still exists? But doesn't q=nCdeltaT, and isn't deltaT 0 in isothermal, so wouldn't it be U=w?

Hi Alex,
For an isothermal reaction, q=-w, as deltaU=0.