Thermodynamics : Isothermal process

[Rohan95]

In principle, what happens when an ideal gas undergoes an isothermal process? How is the gas at a constant temperature; is it maintained at that temperature? If we supply heat to the standard ideal piston assembly, why, or rather how is the heat supplied completely converted to work done by the system? Trying to get bit of a molecular picture here.

Also, what happens if known amount of heat is supplied to ideal gas at known thermodynamic state?

 

[Simon Bridge]

The idealized thermodynamic processes are not easy to realize in real life - in practice, an isothermal process is only approximated.
You are correct, you'd usually have to supply a heat bath, and make changes slowly.

What happens when a known amount of heat is supplied depends on the other constraints - you do this every time you boil water: you know how much heat you supply and you know the thermodynamic state at the start. You may want to look at a simplified situation - say you have a gas in a cylinder/pluger affair you've seen in your textbooks, and you input some heat Q. What happens?

 

[Rohan95]

1) If we supply a heat bath, then we can't control how it will interact with the system, can we? What if some of the heat that is supplied to the system goes to the heat bath?

2) I get that it will depend on other constraints (eg. type of process (constant pressure, constant volume, etc)), but I was wondering what might happen if I supply heat reversibly, without placing any constrains.

 

[Simon Bridge]

1. Some heat supplied to the system will always escape. The experiment design needs to account for this.
i.e. The system may be insulated, and the other state variables allowed to change.

2. There are always constraints... if you do not know, in advance, what the constraints are, then the system will behave unpredictably.