1. Oct 11, 2012

entropy = jouls/kelvin
supose 1 liter of ideal gas is allowed to freely expand into a 2 liter volume in an isolated system
the energy in the system would remain the same,
the temperature in the system would remain the same
therefore if entropy =jouls/kelvin the entropy would remain the same
howerer if 1 liter of ideal gas is allowed to freely expand into a 2 liter volume in an isolated system the entropy does increase.
how dose entropy=jouls/kelvin ?

2. Oct 12, 2012

Andrew Mason

ΔS = ∫dS = ∫dQ/T over a reversible path between the initial and final states.

The initial state is (P,V,T) and the final state is (P/2,2V,T). So to calculate the entropy change you have to find a reversible path between those two states. (hint: the reversible path involves work being done and heat flow into the gas).

AM