If there is constant volume...

[kirsten clemente 1E]

Hi guys,

I am confused about why no work would be done if the volume is constant. I am on question 19 right now, and I got this from the hint, but to me, it still kind of doesn't make any sense. I know that volume= area x distance, deltaU= q + w, and w= -Pressure x deltaVolume but I don't understand how all of this goes hand and hand.

[Chem_Mod]

If you have constant volume, then the piston ceiling can't move. So if I heat my gas up in its container, those gas particles are going to start moving a lot quicker and be more excited!! This is going to increase the pressure inside the container, and try to push the ceiling up. But the ceiling is locked in place, so we can't change the volume by pushing against it. If we can't change the ceiling height by pushing against it, we aren't able to do any work.

-Vivek

[Miles Dailey 1K]

Work can be simply described as a change in volume against a pressure. When volume is constant, the molecules may gain more energy and move faster, but since they do not expand the volume, no work is done.

[Ryan Sebti 3I]

One way you could look at it is purely through the equation, where since W = -P * deltaV, if deltaV (change in volume) is 0, then regardless of pressure work will come out to be zero.

[sherwin arian 1K]

Work is defined as a change in volume against pressure in chemistry. Since the volume isn't changing that means that the molecules can be moving with as much energy as they want but they are not doing any "work" if they do not change the volume of the system; thus the work will be zero.

[Howard Chu 1H]

If you look at the equation w=-Pext(deltaV), if there is no expansion, the value of V would be 0, and anything times 0 would be 0, so no work is being done. Hope this helps!

[405779380]

Think about work as energy being used to change the volume as pressure increases, if the volume is deemed constant, no energy can be used to change the volume and thus no work is being done.