If you are told the initial and final states of a system and the associated change in internal energy, can you determine whether the internal energy change was due to work or to heat transfer? Explain.
Solution 4DQ From the first law of thermodynamics, Q = W + U , where Qis the heat supplied to a system, W is the work done by the system and U is the change in internal energy of the system. Now, U = Q W , this means that the change in internal energy is influenced by heat supplied to the system and the work done by the system. If the system’s volume does not change during the process, then the work done by the system is zero (since W = PV ). Therefore, change in internal energy is completely due to the heat supplied to the system. If it is found that the volume of the system changes, then there will be a certain value of work done by the system. In this case, the change in internal energy may be both due to the heat supplied and the work done by the system.
