[DmytriE]

I know that the energy of the system and the surroundings is conserved but I'm confused about the equation below:

ΔE = q + w

ΔE is the change in energy, q is heat, and w is work. But in the book it describes w is equivalent to PΔV. How exactly does this work? Example? Explaination or a great website with a nice explanation is appreciated!

Thanks!

[Astrokel]

http://apcentral.collegeboard.com/apc/members/courses/teachers_corner/44428.html

It is only true for constant pressure process.

[DmytriE]

Thanks!  That was very helpful.