Ch. 15: 1st Law of Thermodynamics

“the state of a gas” means that

the gas has a specific P, V, n, T (=ideal gas law)

-We assumed that ideal gas particles do not……, thus the system has no…

• In an ideal gas, the total internal energy of the gas particles = ___

• The thermal energy depends only on…

-interact at a distance…. potential energy due to particle interactions

• its thermal energy

• its absolute temperature and on the number of moles of gas

*N=#molecules; n=#moles

Work (W)

-the negative of the area under the pV curve between Vi and Vf

-is an isobaric process, when pressure is a constant and the volume changes, the work done during the process is: W=-pchangeV

-if a gas expands…

-if a gas is compressed…

-changeV>0; W<0

*W<0= energy out of the gas

-changeV<0; W>0

*W>0= energy into gas

-isobaric=

-isochoric=

-same pressure

-same volume

for an isochoric process, W=?

-for an isochoric process, the area under the pV curve is zero, and no work is done (W=0)

*vertical line

Cyclic process

=begins and ends at the same P and V

-the total work done is the area enclosed

-arrows tell you direction; CCW=+

-area of a triangle

-area of a cricle

-A=1/2*base*height

-A=pie*radius²