In the previous box example it is important you understand how we place our system boundaries to calculate the entropy change. If we put a boundary around the surface of the hot body as the heat is lost to the surroundings the temperature will be seen to drop from 200 C to 100 C.. The average being 150 C. The change in entropy (hot body) is then very roughly given by..
ds = Integral{dQ/T} (Integral = Sum of [dQ1/T1 + dQ2/T2 + dQ3/T3 ... ]
~= Q/Taverage)
ds(hot) ~= -Q/150 (-ve for heat out) and for the cold body Taverage = 50 C
ds(cold) ~= Q/50 (+ve heat in)
So ds(total) = Q/50 - Q/150 = Q(3-1)/150 = Q/75 +ve increase.
Note inside the box (closed system) we have two sub-systems each with an OPEN boundary to their surroundings.. The effect of heat flow out of the hot body decreases entropy of the system and the reverse is true for the cold body but they are not equal and the sum is always greater than zero. Establishing for every entropy decrease there must be a greater increase in the surroundings caused by that decrease which gives us the Second Law.
If we now cyclically open the ends of the box first allowing the suns radiant heat to fall on the hot end then cold of space on right end indefinitely you have both entropy drop and increase in open systems powered by the sun working in accordance with the second law. Just like the Earth.
According to evolutionists that's all there is to it.. but is it.
Lets now replace the hot and cold bodies with Nitrogen and Oxygen gasses separated by the same partition but with both at the same temperature and pressure. When we open the partition the gasses will mix by diffusion but no heat is transferred and so..
ds = Integral{dQ/T} = 0 (No change in entropy for whole box)
But the initial separation of gasses is a state of order which the diffusion process, on removing the partition, will destroy. The uniformly mixed gasses will not separate by themselves because it is an irreversible increase in entropy.. All in accordance with the second law..!
No comments:
Post a Comment