Question

The thermodynamic state of a soap film can be described by state variables (T, S) and (σ, A), where σ and A are the surface tension and surface area of the soap film, respectively. When stretching the film, the work done on the system is equal to σdA. The surface tension of the film is found to be a function of temperature only. Around room temperature, it can be expressed as σ(T)=σ0−λT, where σ0 and λ are positive constants.

1) Define three thermodynamic potentials based on the internal energy U, whose natural variables are Tand A, Sand σ, and Tand σ, respectively. Also write down the fundamental equations associated with them.

2) Calculate the internal energy change of the film when it is slowly stretched from area A0 to 2A0 at room temperature.

Please do not copy answer from the other questions on Chegg. Thank you.

Answer 1