Heat energy

صفحه 1:
۹ What is HEAT? ٠ Form of energy and measured in JOULES ٠ Particles move about more and take up more room if heated - this is why things expand if heated ry 0-7 * Itis also why substances change from: solids uids gases en ee 

صفحه 2:
‎cen acd‏ 1ك ‎° The temperature of an object tells us how [07 it is 3 ® Measured in degrees Celsius - ۹ ©» 11 15 ‏5ع2 35 ع0تد5 عط ار‎ ©2617 although the two quantities are re e.g. a beaker of water at 60 °C hotter than a bath of water at 40 ° ‎BUT the bath contains more joul of heat energy ‎ ‎ ‎ ‎ 

صفحه 3:
° If an object has become | cr, it means that it has gained energy. ° If an object cools down, it mean: it has lost energy 

صفحه 4:
¢ Heat energy always moves from: 101 object |) el object e.g.Cup of water at 20 °C in a room at 30°C - gains heat energy and heats up - ‏عون متام توصصطما‎ Cup of water at 20 °C in a room at 10°C loses heat energy and cools down - its temperature will fall. 

صفحه 5:
WEOT EDERGY Senge AMA eT 9 tay Conve: 

صفحه 6:
یل 0() ° Heat is transferred through a.material by being passed from one partic ‏اعم فط‎ 5 ٠» Particles at the warm end move 1 and this then causes the next parti to move faster and so on. © In this way heat in an object travels ۹9 the HOT 95-77 end 

صفحه 7:
® Occurs by the particles hitting each ‏عصة تتعطاه‎ 50 dep mc 11 ® Can happen in solids, liquids a1 ‏ات‎ ° Happens best in solids-particle very close together ® Conduction does not occur very quickly in liquids or gases 

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ON aimed ° Materials that conduct heat ota are called conductors 5 ® All metals are good conductors ‏تا‎ © Copper is a very good conductor heat ° Pans for cooking are usually made with a copper or aluminium bottom and plastic handles 

صفحه 9:
1 ۱ ۱۱۰۱۱ that conduct heat slowly or poorly are called insulators » Glass, wood, plastic and rubber are poor conductors (good insulators) ° Nearly all liquids including water are conductors (good insulators) ۹ ® Gases, including air are poor conductors,e.g., wool feels warm beca' it traps a lot of air ° A fridge has insulation material round it t¢ keep it cold - reduces amount of heat conducted to inside from the warmer roo 

صفحه 10:
رم ۱69 ° Takes place in material where particles can move around inside the material, i.e. liquid or gas ° The heat is carried by the particles themselves moving Convection, tea ag ® Occur because an area with warm particles expands and becomes less dense than the cooler areas nearby. The warm area rises. Cooler particles fall into the space left by the warm particles and convection current is set up 

صفحه 11:
۱6 eh On aa can cd © Hot liquids and gases expand and rise while the cooler liquid or gas falls 2. Goes across 4. And across 

صفحه 12:
ی ‎currents - WINDS‏ ‎During daytime the land warms‏ ® ‎more than the sea. The warm a‏ ‎rises over the land and cool air fa‏ ‎over the sea. So we feel a sea breez‏ ° Rising convection currents can be \ uses by glider pilots to keep their pianes in the air and by birds to stay ‏فاك‎ 

صفحه 13:
13۹ eTizAct ¢ Transfer of heat directly form the source to the object by a wave, travellingvas rays. ° Heat radiation is also known as ~ INFRA-RED ۹ ° All objects 0 ‏و‎ surroundings give out heat as infra-red radiation ° Heat transfer by radiation does not need particles to occur and is the only way ener can be transferred across empty space 

صفحه 14:
حسان) © Hotter objects emit (give out) heat ® Different surfaces emit heat at different speeds ۰4 ‏له‎ energy more quickly - it is a good radiator ° A bright shiny or white surface is a poor radiator © Marathon runners need to keep warm at the end of races, covering in shiny blankets reduces radiation and therefore heat loss. 

صفحه 15:
11111 Dull black can Good Radiator (Caer eee Le a = 4 = - Bright shiny can Poor radiator 

صفحه 16:
۹ » ‏7م0001‎ heat © Substances absorb heat at different speeds ©» Dull, black surfaces absorb heat 2 ° Bright, shiny surfaces absorb heat 07 » 12 ‏أطوطط عتوع17 1م060 ,00112215 نأمط‎ white clothes and paint their houses white to reduce abhsorntion of enerqv 

صفحه 17:
" ©١ - - ۳ = = Lad = = ez 9 = ۳" > -2 Shiny, bright Dull black can can Good absorber Poor absorber 

صفحه 18:
0 04 رصا) 2014 ae Insulator 5 RadiatiN He on ۱۷8 98 ‏ون‎ ‏ايف‎ ‎Conduction n ‏قاری‎ Absorber ‘Emitter 

HEAT ENERGY What is HEAT? • Form of energy and measured in JOULES • Particles move about more and take up more room if heated – this is why things expand if heated • It is also why substances change from: solids liquids gases Visit www.worldofteaching.com for more free powerpoints when heated Heat and Temperature  The temperature of an object tells us how HOT it is  Measured in degrees Celsius - °C  It is NOT the same as heat energy although the two quantities are related. e.g. a beaker of water at 60 °C is hotter than a bath of water at 40 °C BUT the bath contains more joules of heat energy Heating and Cooling  If an object has become hotter, it means that it has gained heat energy.  If an object cools down, it means it has lost energy Heating and Cooling cont…  Heat energy always moves from: HOT object object COOLER e.g.Cup of water at 20 °C in a room at 30°C - gains heat energy and heats up – its temperature rises Cup of water at 20 °C in a room at 10°C loses heat energy and cools down – its temperature will fall. HEAT ENERGY •Energy transfer Conduction Convection Radiation Conduction  Heat is transferred through a material by being passed from one particle to the next  Particles at the warm end move faster and this then causes the next particles to move faster and so on.  In this way heat in an object travels from: the HOT end the cold end Conduction cont…  Occurs by the particles hitting each other and so energy is transferred.  Can happen in solids, liquids and gases,  Happens best in solids-particles very close together  Conduction does not occur very quickly in liquids or gases Conductors  Materials that conduct heat quickly are called conductors  All metals are good conductors of heat  Copper is a very good conductor of heat  Pans for cooking are usually made with a copper or aluminium bottom and plastic handles Insulators/poor conductors  Materials that conduct heat slowly or poorly are called insulators  Glass, wood, plastic and rubber are poor conductors (good insulators)  Nearly all liquids including water are poor conductors (good insulators)  Gases, including air are poor conductors,e.g., wool feels warm because it traps a lot of air  A fridge has insulation material round it to keep it cold – reduces amount of heat conducted to inside from the warmer room Convection  Takes place in material where particles can move around inside the material, i.e. liquid or gas  The heat is carried by the particles themselves moving Convection currents  Occur because an area with warm particles expands and becomes less dense than the cooler areas nearby. The warm area rises. Cooler particles fall into the space left by the warm particles and convection current is set up Convection Currents  Hot liquids and gases expand and rise while the cooler liquid or gas falls 2. Goes across 3. Then down 4. And across 1. Hot air rises Convection cont…  The sun can cause large convection currents - WINDS  During daytime the land warms up more than the sea. The warm air rises over the land and cool air falls over the sea. So we feel a sea breeze.  Rising convection currents can be uses by glider pilots to keep their planes in the air and by birds to stay aloft. Radiation  Transfer of heat directly form the source to the object by a wave, travelling as rays.  Heat radiation is also known as INFRA-RED  All objects thatRADIATION are hotter than their surroundings give out heat as infra-red radiation  Heat transfer by radiation does not need particles to occur and is the only way energy can be transferred across empty space Emitters  Hotter objects emit (give out) heat  Different surfaces emit heat at different speeds  A dull black surfaces loses energy more quickly – it is a good radiator  A bright shiny or white surface is a poor radiator  Marathon runners need to keep warm at the end of races, covering in shiny blankets reduces radiation and therefore heat loss. Emitters of heat Bright shiny can Poor radiator Dull black can Good Radiator Absorbers Cooler objects absorb (take in) heat Substances speeds absorb heat at different Dull, black surfaces absorb heat quickly Bright, slowly In shiny surfaces absorb heat hot countries, people wear bright white clothes and paint their houses Absorbers Shiny, bright can Poor Dull black can Good absorber Key Words Cold Temperat ure Insulator Transf er Heat Conduction Emitter Radiati on Convectio n Conductor Absorber