Two solid copper blocks, Block X and Block Y, are placed in thermal contact inside a perfectly insulated enclosure at time t=0. Block X is initially at 80∘C and Block Y at 20∘C. No phase change occurs and the blocks are otherwise identical.
Answer the following in the context of the time period from t=0 until thermal equilibrium is reached.
(a) Describe qualitatively how the temperatures of the two blocks change with time and how the direction of energy transfer evolves during the process.
(b) Sketch, on clearly labeled axes, an approximate curve of the total entropy Stotal of the two-block system as a function of time. Indicate and label the points corresponding to t=0 and to the moment equilibrium is essentially achieved.
(c) Explain why the slope of your Stotal versus t curve approaches zero as the system nears equilibrium.