Oh God, i keep forgetting to address your question. Yes, they were absolute pressures.

Chestermiller
Mentor
OK. Substitute into the equation, and see what you predict for the temperature change.

Chet

ok, I will do that tomorrow when I get back home... what if my sheet here at school is asking me to calculate the work... like a numerical value? Do i just calculate one side of the equation?

Chestermiller
Mentor
ok, I will do that tomorrow when I get back home... what if my sheet here at school is asking me to calculate the work... like a numerical value? Do i just calculate one side of the equation?

It depends on what work they are referring to. If it is the work that the gas remaining within the container has done in expelling the gas ahead of it past the cork, then, once you know the temperature change, you can calculate the work from ΔU=nCvΔT = -W, where n is the number of moles remaining in the cylinder at final steady state. Of course, you can use the observed temperature change to calculate this. And, of course, this assumes that there is no heat gain by the gas, like, for example, by heat absorbed from the cylinder wall. If the cylinder wall cooled down even a little, this could translate into a large inaccuracy in the calculated work.

chet

It depends on what work they are referring to. If it is the work that the gas remaining within the container has done in expelling the gas ahead of it past the cork, then, once you know the temperature change, you can calculate the work from ΔU=nCvΔT = -W, where n is the number of moles remaining in the cylinder at final steady state. Of course, you can use the observed temperature change to calculate this. And, of course, this assumes that there is no heat gain by the gas, like, for example, by heat absorbed from the cylinder wall. If the cylinder wall cooled down even a little, this could translate into a large inaccuracy in the calculated work.

chet

Thank you! That ws really helpful!