Energy The capacity to do work or transfer

Energy is usually defined as the capacity to do work or transfer heat All forms of energy are either kinetic or potential. Kinetic energy is the energy that results from motion. It is calculated with the equation... 

Although the concept of energy is quite familiar, energy is rather difficult to define precisely. We will define energy as the capacity to do work or to produce heat. In this chapter we will concentrate on the transfer of energy via heat flow that accompanies chemical processes. 

Energy can be transferred between the system and the surroundings as work or heat. Work is the energy expended to move an object against a force. Heat is the energy that is transferred from a hotter object to a colder one. Energy is the capacity to do work or to transfer heat. 

If two blocks of metal, one at a high temperature and the other at a low temp-eramre Tj [Fig. 6.10(a)] are separated by a perfect heat insulator, and the system as a whole is surrounded by a thermal blanket that permits no transfer of heat in or out, then no change in internal energy can occur with time. If the insulator between the blocks is removed, the hotter block will decrdease in temperature and the cooler one will increase in temperature until the uniform temperamre T2 is reached. This transformation is spontaneous. At/ is zero. But a loss of capacity to perform work has occurred. In the initial state, we could insert a thermocouple lead in the block at Ts and another in that at Tj and obtain electrical work. Insertion of thermocouple leads in the same positions in the double block at T2 cannot generate any work. At the conclusion of the spontaneous transformation without the thermocouple, the internal energy is stiU the same as that at the outset, but it is no longer in a condition where it has the capacity to do work. 

Energy The capacity for doing work as measured by the capability of doing work (potential energy) or the conversion of this capability to motion (kinetic energy). Most of the world s convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical or other means in order to accomplish tasks. 

It is standard practice in thermodynamics to divide things up into the system and the surroundings (Frame 1). Figure 7.1 shows two examples. In defining the system we define a definitive boundary. Once this designation is made, thermodynamics then considers the transfer of energy (defined as the capacity to do work, w or transfer heat, q) and matter to and from the system. For this we need to adopt a sign convention. 

It is a property by possessing which the system gets the capacity to do work. It is also defined as any property, which can be produced from or converted into work (e.g., heat). Energy is generally denoted by symbol g . g is positive by convention, if energy is transferred to, i.e., taken up by the system. 

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