Is there an Entropy difference between a cold and hot body

[Chestermiller]

Really? You can get all that from just the two initial temperatures? It makes no difference what the substances are, what their mass is, or what the final temperature is?

Of course you have to specify the masses and heat capacities of the two bodies. I think you must already have known that.

 

[Herman Trivilino]

Of course you have to specify the masses and heat capacities of the two bodies. I think you must already have known that.

Of course I did, which is why I said that without that information you wouldn't have enough information. But you claimed I was wrong when I did that!

 

[Chestermiller]

Ah so you mean an isochor and isotherm and do this continuously until the cold body reaches the final temperature?

I can't understand why you feel compelled to place labels on the processes we are dealing with here, such as adiabatic, isochoric, constant temperature, isothermal, etc. Please stop doing this. The reversible process to take either of these bodies from its initial thermodynamic equilibrium state to its final thermodynamic equilibrium state is not isothermal (since the system temperature is changing), and, for an incompressible solid, the term isochoric is redundant.

If you mean that, to get the body from the initial to the final state reversibly, we can put the body into sequential contact with a series of constant temperature reservoirs at slightly different temperatures, running monotonically from the initial temperature to the final temperature, then this is correct. Is that what you meant?

 

[Chestermiller]

Of course I did, which is why I said that without that information you wouldn't have enough information. But you claimed I was wrong when I did that!

I was unable to read your mind. You certainly didn't mention what information, if any, was missing.

 

[Herman Trivilino]

I was unable to read your mind. You certainly didn't mention what information, if any, was missing.

Huhh? Everything, except what is given, is missing.

Here is the OP's question:

If two bodies, who say start with $T_{cold}=T_c$ and $T_{hot}=T_h$ and then they are brought in contact with one another and then after some time they both have the same temperature. What would be the entropy of the entire system?

My response was to state that there is not enough information given to answer that question.

Your response to me was to contradict that, so I followed up with a clarification and now you are agreeing with me.

 

[alantheastronomer]

Where does this equation exactly come from? Why would the internal energy be zero when there is internal energy in the system? The difference in the internal energy is zero but nonetheless there is internal energy.

The internal energy isn't zero; the CHANGE in internal energy is zero!