Internal Energy (1st Law of Thermodynamics) & Sign Rules

http://www.wikipremed.com/01physicscards.php?card=565

q (+) = heat absorbed (energy is added to the system)

q (—) = heat evolved (energy is subtracted from the system)

W (+) = work done on the system (energy is added to the system)

W (—) = work done by the system (energy is subtracted from the system)

liter atmosphere (L·atm)

a unit of work or energy used in the study of confined gases. The behavior of gases is described, to a first approximation, by the ideal gas law PV = nRT. The ideal gas law is really an energy equation in which the left hand side, pressure P (in atmospheres) times volume V (in liters), measures the potential energy in the confined gas. 1 liter atmosphere is equal to approx. 100 joules...

******uggggghhhh case: W = P x dV = P (atm) x V (L) x (100J/l*atm)