Chemical Thermodynamics 3.2 - Pressure-Volume Work

Short physical chemistry lecture on mechanical pressure-volume work.
When a gas expands against an external pressure, work is done on the surroundings, decreasing the internal energy. When a gas is compressed, work is done on the system, increasing the internal energy.
Notes Slide: i.imgur.com/Cqj...
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[@humor5211]

After a 'idk what i'm studying' semester now I finally understand the pv work.

[@tashitinseltown2557]

Hey:) the mass exerts a force ON the gas due to the gravitational pull so why do we take the force exerted as -mg and not +mg?

[@TMPChem]

I believe this is because we are viewing force from the perspective of the system, and how much force is being exerted on it by the surroundings. In this case, the is a force of mg attempting to compress the system and decrease its volume, hence the negative sign. If the force of gravity were acting to expand the system (as if suspended by a spring), the sign would be reversed.

[@SoumilSahu]

At 1:50 why do you not consider the pressure exerted by the the gas above the piston(i e; from air in the environment )? Or is it considered to be a vacuum?

[@TMPChem]

Whether the pressure is generated by a mass sitting on top of the cylinder in a vacuum, or a gas of constant pressure, the effect will be the same as long as the pressure exerted is the same. Instead of a mass on top of the cylinder, you could imagine a gas of constant pressure mg/A. Both provide a force per unit area which provides resistance as the gas tries to expand, and/or gives the gas energy as it compresses.

[@anilsharma-ev2my]

So what is work done by atmospheric pressure volume in one year ?
Means pressure of the atmospher remains same and volume changing or vice versa

[@KitKatStar17]

does the formula for work change if it is a van der waals gas or an ideal gas for a system with a constant external pressure?

[@mochigojo9753]

May I ask why is the integration form is pVdV instead of just pdV? I assumed the dV came from the delta V or idk.............

[@Joel-sx7if]

P(V) is pressure which is a function of volume. It is not P*V. Like how v(t) is velocity as a function of time

[@jikaikas]

Tnx man

[@muhammadsaleem4086]

nice

[@TMPChem]

Great to hear so.