Overview of the Laws of Thermodynamics
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Thermodynamics is the branch of physics that is concerned with the flow of heat and work and
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Overview of the Laws of Thermodynamics

Hello, I'm John for About.com, today I am going to be highlighting some of the key concepts of the Laws of Thermodynamics. Thermodynamics is the branch of physics that is concerned with the flow of heat and workand their effects on energy. The term “thermodynamics” comes from the greek words therme,meaning heat, and dynamis, meaning power, and was coined in during the development of the steam engine. Thermodynamics states that if two bodies, A and B, are in thermalequilibrium with a third body, C, then bodies A and B must also be in thermal equilibrium with each other. For example two bottles of soda kept in a cooler of ice water will reach the same temperature as the ice water and have the same temperature as each other. At this point no heat will flow between the water and the soda or between the sodas. First Law of Thermodynamics is an example of the physical principle of the Law of Conservation of Energy, which states that energy can neither be created nor destroyed, only converted into other forms. The energy of a system will change only when heat or work is added or removed. Your body is an example of such a system. In order to move (do work) and maintain your body temperature (produce heat) you must add chemical energy in the form of food. No energy in ultimately means no heat or work out. The Second Law of Thermodynamics states that heat energy can move from areas of higher temperature to areas of lower temperature spontaneously, but that the movement of heat energy from areas of low temperature to areas of high temperature requires an addition of energy. Your house on a hot day is an example. The heat from outside will move into a coolhouse by itself. To move the heat outside, where it is hotter you have to use an air conditioner which uses energy to push the heat out. The Third Law of Thermodynamics uses the concept of entropy- the amount of random particle motion in a system to define the Absolute, or Kelvin temperature scale. When there is no molecular motion at all, (a condition that only occurs in theory) the entropy is zero and the temperature is defined as absolute zero. As the temperature increases, particle motion and entropy and temperature all increase. As a result, Kelvin temperatures and entropy values are always positive. Thank you for watching. For more information, please visit About.com.

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