![]() ![]() Fatigue, therefore, is not a state function. These conditions would influence changes in the hiker’s fatigue level, which depends on the path taken and the conditions experienced. On the other hand, a person may or may not carry a heavy pack and may climb in hot weather or cold. If both hikers start from the same point at the base of the mountain and end up at the same point at the top, their net change in altitude will be the same regardless of the path chosen. ![]() If the person is well trained and fit, he or she may be able to climb almost vertically to the top (path A), whereas another less athletic person may choose a path that winds gradually to the top (path B). To help understand the concept of a state function, imagine a person hiking up a mountain ( Figure 18.1 "Altitude Is a State Function"). Thus a change in a state function depends on only the difference between the initial and final states, not the pathway used to go from one to the other. In Chapter 5 "Energy Changes in Chemical Reactions", we also introduced the concept of a state function A property of a system whose magnitude depends on only the present state of the system, not its previous history., a property of a system that depends on only the present state of the system, not its history. (For more information on reaction rates and kinetics, see Chapter 14 "Chemical Kinetics".)Įquation 18.1 system + surroundings = universeĪ closed system, such as the contents of a sealed jar, cannot exchange matter with its surroundings, whereas an open system can in this case, we can convert a closed system (the jar) to an open system by removing the jar’s lid. The rate of a reaction and its pathway are described by chemical kinetics. It does not, however, say anything about whether an energetically feasible reaction will actually occur as written, and it tells us nothing about the reaction rate or the pathway by which it will occur. Thermodynamics tells chemists whether a particular reaction is energetically possible in the direction in which it is written, and it gives the composition of the reaction system at equilibrium. ![]() (from the Greek thermo and dynamic, meaning “heat” and “power,” respectively), the study of the interrelationships among heat, work, and the energy content of a system at equilibrium. Our goal in this chapter is to extend the concepts of thermochemistry to an exploration of thermodynamics The study of the interrelationships among heat, work, and the energy content of a system at equilibrium. In Chapter 5 "Energy Changes in Chemical Reactions", you also learned about thermochemistry, the study of energy changes that occur during chemical reactions. ![]() For example, the energy stored in chemical bonds can be released as heat during a chemical reaction. (For more information on energy, see Chapter 5 "Energy Changes in Chemical Reactions".) Instead, energy takes various forms that can be converted from one form to another. The second, the law of conservation of energy, states that energy can be neither created nor destroyed. (For more information on matter, see Chapter 1 "Introduction to Chemistry".) The law of conservation of mass is the basis for all the stoichiometry and equilibrium calculations you have learned thus far in chemistry. The first of these, the law of conservation of mass, states that matter can be neither created nor destroyed. Chemical reactions obey two fundamental laws. ![]()
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