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Heat and temperature

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Heat and temperature

  1. 1. HEAT ANDHEAT ANDTEMPERATURETEMPERATUREAutora: Marta García T.Autora: Marta García T.
  2. 2. WHAT IS HEAT?WHAT IS HEAT? HeatHeat is thermal energy transferred from ais thermal energy transferred from awarmer body or system, to a colder one. So,warmer body or system, to a colder one. So,one system releases heat and the other oneone system releases heat and the other oneabsorbs it.absorbs it. This thermal transfer will stop when bothThis thermal transfer will stop when bothsystems have the same temperature (systems have the same temperature (thermalthermalequilibriumequilibrium).).http://www.quimicaweb.net/grupo_trabajo_ccnn_2/tema3/index.htmAutora: Marta García T.Autora: Marta García T.
  3. 3. Just to think a bit….Just to think a bit….a)a) Is it correct to say that hot objects emit heatIs it correct to say that hot objects emit heatand cold objects emit cold?and cold objects emit cold?b)b) Is it true that a blanket give us heat?Is it true that a blanket give us heat?c)c) What direction does heat flow in?:What direction does heat flow in?:Autora: Marta García T.Autora: Marta García T.
  4. 4.  There are two units of measure for heat:There are two units of measure for heat: JoulesJoules (J)(J) CaloriesCalories (cal)(cal) 1J = 0,24 cal1J = 0,24 calAutora: Marta García T.Autora: Marta García T.
  5. 5. WHAT IS TEMPERATURE?WHAT IS TEMPERATURE? TemperatureTemperature is the amount of heat in a bodyis the amount of heat in a bodyor system.or system.• The instrument which measuresThe instrument which measurestemperature is thetemperature is the thermometerthermometer..Autora: Marta García T.Autora: Marta García T.
  6. 6.  There are three scales to measure temperature:There are three scales to measure temperature: Celsius ScaleCelsius Scale: is the most common scale. It is: is the most common scale. It isdivided into a hundred parts, from the freezing pointdivided into a hundred parts, from the freezing pointof water (0 ºC) to the boiling point (100 ºC).of water (0 ºC) to the boiling point (100 ºC). Fahrenheit ScaleFahrenheit Scale: used in English-speaking: used in English-speakingcountries. The freezing point of water is 32 ºF, andcountries. The freezing point of water is 32 ºF, andthe boiling point is 212 ºF.the boiling point is 212 ºF. Kelvin ScaleKelvin Scale: used by scientists. The freezing point: used by scientists. The freezing pointof water is 273 K, and the boiling point is 373 K.of water is 273 K, and the boiling point is 373 K.Autora: Marta García T.Autora: Marta García T.
  7. 7. Autora: Marta García T.Autora: Marta García T.
  8. 8. HOW DOES HEATHOW DOES HEATTRANSFER?TRANSFER? There are three ways for heat to beThere are three ways for heat to betransferred, depending on the material:transferred, depending on the material: ConductionConduction: this process occurs in most solids.: this process occurs in most solids.Heat is transferred by direct contact.Heat is transferred by direct contact.Autora: Marta García T.Autora: Marta García T.
  9. 9.  ConvectionConvection: occurs in liquids and gasses. Heat: occurs in liquids and gasses. Heatis transferred by the movement of currents.is transferred by the movement of currents.Autora: Marta García T.Autora: Marta García T.
  10. 10.  RadiationRadiation: is the transfer of heat by: is the transfer of heat byelectromagnetic waves. Contact between theelectromagnetic waves. Contact between thesource and the heated substance is notsource and the heated substance is notnecessary, so is the way heat transfers in thenecessary, so is the way heat transfers in theuniverse (where there is no matter).universe (where there is no matter).Autora: Marta García T.Autora: Marta García T.
  11. 11. Label this pictureLabel this pictureabout heat transfer:about heat transfer:http://www.profes.net/varios/videos_interactivos/definitivo.swfAutora: Marta García T.Autora: Marta García T.
  12. 12. WHAT ARE THE EFFECTS OFWHAT ARE THE EFFECTS OFHEAT?HEAT?1)1) Changes of States:Changes of States: EndothermicEndothermic: changes produced by heat: changes produced by heatabsorption: melting, evaporation andabsorption: melting, evaporation andsublimation.sublimation. ExothermicExothermic: changes produced by heat loss:: changes produced by heat loss:solidification, condensation and regressivesolidification, condensation and regressivesublimation.sublimation.Autora: Marta García T.Autora: Marta García T.
  13. 13. Do you remember theDo you remember thenames for the changesnames for the changesof state?of state?Autora: Marta García T.Autora: Marta García T.
  14. 14. 2)2) ExpansionExpansion: it is the increase in volume which: it is the increase in volume whichoccurs when a system gains heat. Particlesoccurs when a system gains heat. Particlesmove faster, so they occupy more space.move faster, so they occupy more space.3)3) ContractionContraction: it is the decrease in volume which: it is the decrease in volume whichoccurs when a system cools. Particles moveoccurs when a system cools. Particles movemore slowly, so they occupy less space.more slowly, so they occupy less space.http://www.educared.net/aprende/anavegar3/premiados/ganadores/c/651/Calor/index.htmAutora: Marta García T.Autora: Marta García T.

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