浙大必威体育精装版化工原理课件-post+2+thermochemistry介绍.ppt

* * * * * * * * * * * * * * * * * * Thermochemistry Chapter 6 Energy change of chemical reaction. Thermal energy the random motion. Chemical energy the bonds of substances Nuclear energy: neutrons and protons in the atom Electrical energy: the flow of electrons Potential energy: virtue of an object’s position It is the capacity to do work, What is the Energy? and exists in a variety of the forms. No one knows how much the exact energy is! The thermodynamics deals only with the energy changes that accompany chemical reactions. System and Surroundings System is the specific part of the universe that is of interest in the study. Open system mass energy exchanged closed system only energy exchanged Isolated system Nothing exchanged (1) Heat is the energy transfer between a system and its surroundings that are at different temperatures. What we can measure is only the energy change! Temperature is a measure of the thermal energy. Temperature = Thermal Energy 900C 400C greater thermal energy ? (2) Work, like heat, is the energy transfer between a system and its surroundings. Work (w) = Force (F) ? distance (h) = P ? A ? h h A A = P DV Pressure-volume work Thermodynamics State functions determined only by the system state, regardless of how it was achieved (i.e. history). The potential energy of hiker 1 is the same as that of hiker 2. Energy change: DE = Efinal - Einitial Other changes: DP = Pfinal - Pinitial DV = Vfinal - Vinitial DT = Tfinal - Tinitial Significance it makes the reasoning and calculation simple. DE = q + w q: the heat exchange with the surroundings. Attention: E is a state function, but q and w are not a state function, since the latter two are only related to a process. The First Law of Thermodynamics: The energy of the universe can be converted from one form to another, but it can not be created or destroyed. w: the work done on (or by) the system. “+” gain by the syste