Agas is compressed from 600 cm3 to 200cm3 at a constant pressure of 400 kpa. at the same time, 100 j of heat energy is transferred out of the gas. part a what is the change in thermal energy of the gas during this process?

The initial volume of the gas is

while its final volume is

so its variation of volume is


The pressure is constant, and it is


Therefore the work done by the gas is

where the negative sign means the work is done by the surrounding on the gas.

The heat energy given to the gas is


And the change in internal energy of the gas can be found by using the first law of thermodynamics:

where the positive sign means the internal energy of the gas has increased.