Consider insulated canister with 20 molecules inside. At one instant (let's call it SA) you observe that 11 molecules are in the upper half of the canister and 9 are in lower half of the canister. At another instant (let's call it SB) you see that 3 molecules are in lower half of the canister and 17 are in upper half.

a) Which state is more likely to happen? Why

b) Compare entropies of the two states

 

c) Which situation you think is more likely to happen first, after you put 20 molecules into the box? Why? 

d) In most general terms what will need to happen to transition from SB to SA