THERMODYNAMICS AND THERMOCHEMISTRY
Thermodynamics and Energy.
The energy of a body may be defined broadly as its capacity for doing work. This energy may take various forms, such as kinetic energy of a body in motion, potential energy due to position, heat energy as measured by the temperature, electrical energy, chemical energy, etc. Chemical and physical processes are almost invariably accompanied by energy changes, and results of considerable importance have been obtained studying the laws underlying these changes. It is this study of energy transformation which constitutes the subject matter of thermodynamics. Although thermodynamics may appear to be somewhat theoretical in nature, the two laws have led to results of fundamental importance to chemistry, as well as to physics.
Conservation of Energy: The First Law of Thermodynamics.
Many attempts have been made from time to time to realize "perpetual motion", that is, the continuous production of mechanical work without supplying an equivalent amount of energy from another source. The failure of all such efforts has led to the universal acceptance of the principle of conservation of energy. This principle has been stated in many forms, but essentially they amount to the fact that although energy can be converted from one form to another, it cannot be created or destroyed or, alternatively, whenever a quantity of one kind of energy is produced, an exactly equivalent amount of other kinds must disappear. It is evident that perpetual motion, in the generally accepted sense of the term, would be contrary to this principle, for it would involve the creation of energy. Further, the exact equivalence of mechanical or electrical work and heat, as found by Joule and others, is a necessary consequence of the same principle.
The law of conservation of energy is purely the result of experience, no exception to it having as yet been found. The assumption that it is of universal applicability is the basis of the first law of thermodynamics. This law can be stated in any of the ways given above for the principle of the conservation of energy, or else it may be put in the following form. The total energy of a system and its surroundings must remain constant, although it may be changed from one form, to another.