Consider the systems shown in Figure. In one case the battery becomes completely discharged by running the current through a heater and in the other case by running a fan. Both processes occur at constant pressure. In both cases the change in state of the system is the same: The battery goes from being fully charged to being fully discharged. Yet in one case the heat evolved is large, and in the other it is small. Is the enthalpy change the same in the two cases? If not, how can enthalpy be considered a state function? If it is, what can you say about the relationship between enthalpy change and q in this case, as compared with others that we have considered?
If the battery is defined as the system, what is the sign on w in part (b)?
Figure Internal energy is a state function, but heat and work are not. (a) A battery shorted out by a wire loses energy to the surroundings only as heat; no work is performed. (b) A battery discharged through a motor loses energy as work (to make the fan turn) and also loses some energy as heat. The value of _E is the same for both processes even though the values of q and w in (a) are different from those in (b).
Ch. 3 Quantum Theory and Electronic Structures 1. Forms of energy a. Kinetic energy – energy from motion i. Ek = 1/2m(v^2) ii. Kinetic energy = one half of the mass times velocity squared iii. Thermal energy (form of kinetic energy)– associated with the random motion of atoms and molecules b. Potential...