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Heat
HeatHeat is the energy that flows between two objects because of a difference in temperature. Heat always flows from a body at a higher temperature to one at a lower temperature. Scientists use the term heat differently than do nonscientists. The average person may think of heat as the amount of energy contained in a body. The correct term for that property, however, is thermal energy. Thermal energy and temperatureAccording to the kinetic theory of matter, all matter is composed of particles that are constantly in motion. Temperature is a measure of the motion of those particles. The more rapidly particles are in motion, the higher the temperature; the less rapidly they are moving, the lower the temperature. In theory, it would be possible to reduce the motion of the particles in an object to zero. In that case, the object would contain no thermal energy. The temperature at which all particle motion ends is called absolute zero. Scientists have come within a few millionths of a degree of absolute zero but have never actually reached that point. Heat TransferAnother way to think of heat is as a transfer of thermal energy from one place to another. This process occurs in one of three ways: conduction, convection, and radiation. Conduction. Conduction is the process of heat transfer. Rapidly moving molecules in a hot material collide with slower moving molecules in a cool material. The fast-moving molecules slow down and the slow moving molecules increase their speed. Conduction occurs, then, when two bodies of different temperatures are in contact with each other. Convection. Convection is the process by which large masses of a fluid (a liquid or gas) move, carrying thermal energy. When water in a container is heated, for example, it expands. Cooler water around it pushes the lighter water upward. As the warm water rises, it begins to cool and starts to move downward in the liquid again. Eventually, a circular motion is produced within the liquid, forcing heat to be transferred throughout the liquid. Radiation. Finally, thermal energy can be transferred by radiation. Hot bodies emit electromagnetic radiation that corresponds to their temperature. This radiation passes through space until it comes into contact with a body with less thermal energy. The cooler body then absorbs this radiation and becomes warmer. Transfer of thermal energy. The transfer of thermal energy from one place to another occurs in one of three ways: conduction, convection, and radiation. In conduction, rapidly moving molecules in a hot material collide with slower moving molecules in a cool material. The fast-moving molecules slow down and the slow-moving molecules increase their speed. Conduction occurs, then, when two bodies of different temperatures are in contact with each other. Convection is the process by which large masses of a fluid (a liquid or gas) move, carrying thermal energy. When water in a container is heated, for example, it expands. Cooler water around it pushes the lighter water upward. As the warm water rises, it begins to cool and starts to move downward in the liquid again. Eventually, a circular motion is produced within the liquid, forcing heat to be transferred throughout the liquid. Finally, thermal energy can be transferred by radiation. Hot bodies emit electromagnetic radiation that corresponds to their temperature. This radiation passes through space until it comes into contact with a body with less thermal energy. The cooler body then absorbs this radiation and becomes warmer. Heat unitsSince heat is a form of energy, the units used to measure heat are the same as those used to measure energy. In the metric system, one of the earliest units used to measure heat was the calorie. The calorie is defined as the amount of heat energy needed to raise the temperature of one gram of water one degree Celsius. To be precise, the temperature change is specified as an increase from 14.5°C to 15.5°C. In the International System of Units (the SI system), the unit of energy is the joule. A calorie is defined as 4.184 joules. Specific heatMaterials differ from each other with regard to how easily they can be warmed. One could add a joule of heat to a gram of water, a gram of iron, a gram of mercury, and a gram of ethyl alcohol and notice very different results. The temperature of the mercury would rise the most, and the temperature of the water would rise the least. The specific heat capacity (or just specific heat) of a material is defined as the amount of heat required to raise the temperature of one gram of the material one degree Celsius. It takes 4.18 joules to raise the temperature of 1 gram of water 1 degree Celsius (at a temperature of 25°C). In comparison, it takes only 0.14 joule to raise the temperature of the same amount of mercury by one degree Celsius and 0.45 joule to raise the temperature of the same amount of iron by one degree Celsius. It takes 2.46 joules to raise the temperature of the same amount of ethyl alcohol by one degree Celsius. [See also Energy; Temperature; Thermodynamics ] |
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"Heat." UXL Encyclopedia of Science. 2002. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "Heat." UXL Encyclopedia of Science. 2002. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1G2-3438100351.html "Heat." UXL Encyclopedia of Science. 2002. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3438100351.html |
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heat
heat nonmechanical energy in transit, associated with differences in temperature between a system and its surroundings or between parts of the same system.
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"heat." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "heat." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1E1-heat.html "heat." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-heat.html |
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Heat
200. Heat
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"Heat." -Ologies and -Isms. 1986. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "Heat." -Ologies and -Isms. 1986. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1G2-2505200211.html "Heat." -Ologies and -Isms. 1986. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-2505200211.html |
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Heat
HeatHeat is the transfer of energy that results from the difference in temperature between a system and its surroundings. At a molecular level, heat is the transfer of energy that makes use of or stimulates disorderly molecular motion in the surroundings. For instance, when a hydrocarbon fuel burns, the energy released in the reaction stimulates the surrounding atoms and molecules into more vigorous random motion, and we refer to this escape of energy as heat. Heat is not stored: Heat is energy in transit. The measurement of quantities of energy transferred as heat is called calorimetry. Such a measurement is commonly made by observing the rise in temperature caused by the process being studied and interpreting that rise in terms of the heat produced. Calorimetry is used to measure the changes in internal energy and enthalpy that accompany chemical reactions. The field of study is called thermochemistry, and it is used to assess the efficacy of fuels, the energy flow in chemical plants, and the strengths of chemical bonds. Measurements of the heat produced or absorbed by chemical reactions are central to thermodynamics, and to assessments of whether or not a particular reaction will tend to occur. In thermodynamics, the quantity of energy transferred as heat as a result of a chemical reaction is identified with the change in the internal energy of the system if the transfer takes place without change in the system's volume, and with the change in enthalpy of the system if the transfer takes place at constant pressure. The energy or enthalpy change accompanying a chemical reaction that is inaccessible to measurement may be determined by using Hess's law, which states that the enthalpy change accompanying a chemical reaction can be regarded as the sum of the enthalpy changes of the reactions into which the overall reaction may be divided. Hess's law is no more than a special application of the first law of thermodynamics. The source of heat as a fuel burns is the energy released when the bonds characteristic of the reactants are replaced by the bonds characteristic of the products. Energy is released when hydrocarbons burn because of the great strengths of the oxygen–hydrogen and oxygen–carbon bonds that are formed in the products (water and carbon dioxide), replacing the relatively weak carbon–hydrogen and carbon–carbon bonds of the fuel. Ultimately, the energy of burning fuel is the energy released as the electrons and atomic nuclei settle into more favorable arrangements (just as nucleons do in the much more exothermic processes accompanying nuclear rearrangements). Although the term "heat energy" is commonly encountered in casual conversation, strictly speaking there is no such entity. The term is commonly used in place of the more precise term "energy of thermal motion," where thermal motion is random molecular motion, as in the motion of molecules in a gas. Nor is heat stored: Only energy is stored, and heat is one of the modes by which it may be increased or extracted. see also Chemistry and Energy; Energy; Explosions; Temperature; Thermochemistry; Thermodynamics. Peter Atkins BibliographyAtkins, Peter, and de Paula, Julio (2002). Atkins' Physical Chemistry, 7th edition. New York: Oxford University Press. Smith, Crosbie (1998). The Science of Energy: A Cultural History of Energy Physics in Victorian Britain. Chicago: University of Chicago Press. |
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Atkins, Peter. "Heat." Chemistry: Foundations and Applications. 2004. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. Atkins, Peter. "Heat." Chemistry: Foundations and Applications. 2004. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1G2-3400900232.html Atkins, Peter. "Heat." Chemistry: Foundations and Applications. 2004. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3400900232.html |
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heat
heat / hēt/ • n. 1. the quality of being hot; high temperature: it is sensitive to both heat and cold. ∎ hot weather conditions: the oppressive heat was making both men sweat. ∎ a source or level of heat for cooking: remove from the heat and beat in the butter. ∎ a spicy quality in food that produces a burning sensation in the mouth: chili peppers add taste and heat to food. ∎ Physics heat seen as a form of energy arising from the random motion of the molecules of bodies, which may be transferred by conduction, convection, or radiation. ∎ technical the amount of heat that is needed to cause a specific process or is evolved in such a process: the heat of formation. ∎ technical a single operation of heating something, esp. metal in a furnace. 2. intensity of feeling, esp. of anger or excitement: words few men would dare use to another, even in the heat of anger. ∎ (the heat) inf. intensive and unwelcome pressure or criticism, esp. from the authorities: a flurry of legal proceedings turned up the heat in the dispute. 3. a preliminary round in a race or contest: the 200-meter heats. • v. make or become hot or warm: [tr.] the room faces north and is difficult to heat | [intr.] the pipes expand as they heat up. ∎ [intr.] (heat up) (of a person) become excited or impassioned. ∎ [intr.] (heat up) become more intense and exciting: the action really begins to heat up. ∎ [tr.] archaic inflame; excite: this discourse had heated them. PHRASES: in the heat of the moment while temporarily angry, excited, or engrossed, and without stopping for thought. in heat (of a female mammal) in the receptive period of the sexual cycle; in estrus. |
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"heat." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "heat." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O999-heat.html "heat." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-heat.html |
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heat
heat (symbol Q) Form of energy that transfers as a consequence of a difference in temperature. The amount of heat gained or lost by a body equals the product of its heat capacity and the temperature through which it rises or falls. Heat transfers in three forms: convection (within fluids), conduction (within objects), and radiation. The total kinetic and potential energy of a body is its internal energy (U). If this body changes temperature, there is a corresponding change (ΔU) in its internal energy. According to the first law of thermodynamics, Δ = Q−W, where Q is the heat and W is the work. The SI unit of heat and energy is the joule(J).
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"heat." World Encyclopedia. 2005. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "heat." World Encyclopedia. 2005. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O142-heat.html "heat." World Encyclopedia. 2005. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-heat.html |
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heat
heat if you don't like the heat get out of the kitchen proverbial saying, mid 20th century, meaning that if you choose to work in a particular sphere you must also deal with its pressures; particularly associated with President Truman (1884–1972).
in the heat of the moment while temporarily angry, excited, or engrossed, and without stopping for thought. See also white heat. |
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ELIZABETH KNOWLES. "heat." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. ELIZABETH KNOWLES. "heat." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O214-heat.html ELIZABETH KNOWLES. "heat." The Oxford Dictionary of Phrase and Fable. 2006. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O214-heat.html |
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heat
heat sb. OE. hǣtu = MDu. hēte, OHG. heizi :- WGmc. *χaitīn. f. Gmc. *χaitaz HOT; also OE. hǣte (:- *χaitja).
So heat vb. OE hǣtan. |
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T. F. HOAD. "heat." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "heat." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O27-heat.html T. F. HOAD. "heat." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-heat.html |
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HEAT
HEAT abbr.high explosive antitank (denoting a class of warheads).
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"HEAT." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "HEAT." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O63-HEAT.html "HEAT." The Oxford Essential Dictionary of the U.S. Military. 2001. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O63-HEAT.html |
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heat
heat
•accrete, beat, beet, bittersweet, bleat, cheat, cleat, clubfeet, compete, compleat, complete, conceit, Crete, deceit, delete, deplete, discreet, discrete, eat, effete, élite, entreat, escheat, estreat, excrete, feat, feet, fleet, gîte, greet, heat, leat, leet, Magritte, maltreat, marguerite, meat, meet, mesquite, mete, mistreat, neat, outcompete, peat, Pete, petite, pleat, receipt, replete, seat, secrete, sheet, skeet, sleet, splay-feet, street, suite, sweet, teat, treat, tweet, wheat
•backbeat • heartbeat • deadbeat
•breakbeat • offbeat • browbeat
•downbeat • drumbeat • upbeat
•sugar beet • Blackfeet • flatfeet
•forefeet • exegete • polychaete
•lorikeet • parakeet
•athlete, biathlete, decathlete, heptathlete, pentathlete, triathlete
•kick-pleat • paraclete • obsolete
•gamete • crabmeat • sweetmeat
•mincemeat • forcemeat • backstreet
•concrete • window seat
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"heat." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 26 May. 2012 <http://www.encyclopedia.com>. "heat." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (May 26, 2012). http://www.encyclopedia.com/doc/1O233-heat.html "heat." Oxford Dictionary of Rhymes. 2007. Retrieved May 26, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-heat.html |
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