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OBJECTIVES

H E A T. OBJECTIVES. MATTER. EVALUATION. Standard competency and Basic Competency. H E A T. Standard Competency. : Comprehending states of matter and its change. Basic Competency. Describe role of heat in changes states of matter and temperature’s substance

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OBJECTIVES

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  1. HEAT OBJECTIVES MATTER EVALUATION

  2. Standardcompetencyand BasicCompetency HEAT StandardCompetency : Comprehendingstatesofmatter andits change BasicCompetency • Describeroleofheatinchanges • statesofmatterand temperature’ssubstance • alsoits applicationindailylife

  3. 3 • BLack’s Principle • Heat and Change State • Heat and Change Temperature • What is HEAT?

  4. HEAT AND TEMPERATURE Areheatenergyandtemperaturejustthesamething? No!Let'sgetthisclear: Heatistheenergystoredinsidesomething. Temperatureisameasurementofhowhotorcold somethingis. Anobject'stemperaturedoesn'ttellushowmuchheat energyithas.

  5. HISTORY OF HEAT 5 •Beforethe9thcentury,manyscientist believedthatheatwasafluid. •HeatasfluidfirstlystatedbyAntoine LaurentLavoisier,Hesaidthatwhena hotterobjectwasincontactwiththe colderobject,thenthefluidwouldflow •Somescientistdisagreedwiththeconcept ofHeatasfluid.Thosescientistprovedthat Heat was not a fluid, but a form of Energy AntoineLavoiser

  6. What Is Heat? 6 Heatenergyisthetotalenergyofparticlescomposinga matter. Heatisoneformofenergywhichisflowingfromanobjectwith highertemperaturetoanotherobjectwithlowertemperature TheunitofHeatisJoule(J) Heatisalsoexpressedinunitsofcalories. Onecaloriedefinedastheamountofheatneededtoheat1 gramofwateruntilitstemperatureincreasing1C°. 1calorie=4.2joules 1joule=0.24calories

  7. Heat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature.e.g: tea, coffee • Cold objects in a warmer room will heat up to room temperature.e.g: butter, ice

  8. What do you think?

  9. Forms of Heat Transfer

  10. Radiation How does heat energy get from the Sun to the Earth? There are no particles between the Sun and the Earth so it MUST travel by radiation RADIATION ?

  11. Radiation • The transfer of heat in rays, from a hot object, without needing a medium to pass through • It travels in all directions from a hot object • The hotter an object is, the more heat it will radiate out • Does the surface affect the way heat is radiated?

  12. What colour should we paint radiators?Which colour is better to wear on a sunny day?black or white? • A dull black surface will radiate and absorb heat better than a bright shiny surface.

  13. Dull metal Shiny black Shiny metal Dull black Four containers were filled with warm water. Which container would have the warmest water after ten minutes? shiny metal The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation. radiation dull black emitting

  14. Radiation – Think Pair-Share Radiation travels in straight lines True/False Radiation can travel through a vacuum True/False Radiation requires particles to travel True/False Radiation travels at the speed of light True/False

  15. Radiation questions Why are houses painted white in hot countries? White reflects heat radiation and keeps the house cooler. Why are shiny foil blankets wrapped around marathon runners at the end of a race? The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold.

  16. Conduction • Transfer of heat is through a SOLID by being passed from one particle to the next • Particles at the warm end move fasterand this then causes the next particles to move faster and so on. e.g: poker in fire spoon in tea • In this way heat in an object travels from:the HOT end the cold end

  17. Conduction • When you heat a metal strip at one end, the heat travels to the other end. • As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

  18. Conductors/Insulators • If a substance easily allows heat to move through it, we can say it is a good conductor of heat. e.g: most metals • If a substance does not allow heat to pass through it easily we can say it is an Insulator. E.g: wood, plastic, glass • Why do many sauce pans have plastic handles?

  19. Conduction V Insulation

  20. Conductor or Insulator? • Wood? • Aluminium? • Plastic? • Glass? • Iron? • Polystyrene? • Copper? • Cardboard?

  21. Convection What happens to the particles in a liquid or a gas when you heat them? The particles spread out and become less dense. A liquid or gas.

  22. Convection • It is the way in which particles in a GAS or LIQUID move upwards, carrying heat with them • Think about when you boil water, the bubbles move upwards • Or think of a gas heater in the room, the heat rises around the room

  23. Convection Cools at the surface Convection current Cooler water sinks Hot water rises

  24. Convection Where is the cooling compartment put in a fridge? Cooling compartment It is warmer at the bottom, so this warmer air rises and a convection current is set up. It is put at the top, because cool air sinks, so it cools the food on the way down.

  25. Should a radiator be called a radiator?

  26. Convection questions Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Why are boilers placed beneath hot water tanks in people’s homes? Hot water rises. So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

  27. Heat and the change 7 oftemperature Notallsubstanceshavethesameabilityinabsorbing heat. Theabilitytoabsorbheatdeterminedbythenatureof asubstancecalledspecifichetcapacity. SpecificHeatCapacity(c) Thespecificheatcapacityofasubstanceis definedastheheatrequiredtoraisingthe temperatureof1kgofthesubstanceby1°C. Theunitofspecificheatcapacityisjouleperkilogram perCelsiusdegree(J/kgC°)

  28. Specifik Heat Capacity 8 Thisprovedthatheatneededtoraisethe temperatureof1C°alcoholissmaller thantheheatneededtoraisewater temperatureat1C°.Thatis,alcohol heat faster than water.

  29. Calculating Heat 9 Theamountofheat(Q)requiredbyanobjectisproportionalto themassoftheobject(m),dependingonthespecificheatcapacity (c),andcomparabletotheincreaseintemperature(∆T). Thechangeofheat(receivedheatorreleasedheat)ofa substancecannotbemeasureddirectly,butitcanbecalculated usingthefollowingequation. Q=mxcxΔT Notes: Q=heatreceivedorreleased(Joules) m=mass(kg) c=specificheatcapacity(J/kgC°) ΔT=changesoftemperature(C°)

  30. Example 10 Calculateheatneededtoincreasingtemperatureof500g waterfrom20°Cto100°C,ifthespecificheatofwateris 4200J/kgC°? Given: m=500g=0.5kgc=4200J/kgC° ∆T=100°C-20°C=80C° Question:Q=…? Answer: Q=mxcx∆T =0.5kgx4200J/kgC°x80C° =168,000J Sotheheatreceivedbythewateris168,000J

  31. Heat Capacity (C) Theheatcapacityofasubstanceisdefinedas theamountofheatrequiredtoraiseitstemperature by1C° UnitofHeatcapacityisJoulesperCelsiusdegree(J/C°) Heatcapacitycanbecalculatedusingthefollowingequations. C=m×c Notes: Q ∆T C=Heatcapacity(J/C°) m=mass(kg) Q=heatreceivedorreleased(Joules) c=specificheatcapacity(J/kgC°) ∆T=changesoftemperature(C°) C=

  32. change of temperature Problems of Heat and the 12 Answerthesefollowingquestions! 1.Twocontainersofthesamesizearefilledwithwaterandsand respectively.Iftheyareexposedtothesunheat,whichonegets hottermorequickly?Why? 2.You’reheatinga3.0kgglassblock,specificheatcapacityof840 J/(kg.C°),raisingitstemperatureby60C°.Whatheatdoyouhave toapply? 3.2kgofironisheatedfrom15°Cto30°C.Iftheheatrequiredis 13,500J,whatisspecificheatcapacityofiron? 4.42kilojoulesofheatreleasedfromthe2kgoficeattemperatures- 15°C.Whatisthetemperaturefinally,ifthespecificheatofice is2100J/kg.C° 5.Toraisethetemperatureofanobjectfrom10°Cto40°C,it requiredheat60,000J.Calculatetheheatcapacityofitsobject!

  33. Heat and the change State of Matter 13 •Whenamatterchangeitsstate,the temperature does not increasealthoughthe heatiscontinuouslygiven. •Theheatisusedtochangingthestateofmatter. •Theheatusedforchangingthestateofmatteris calledLatentheat.

  34. STATES OF MATTERSOLIDS • Particles of solids are tightly packed, vibrating about a fixed position. • Solids have a definite shape and a definite volume. Heat

  35. STATES OF MATTERLIQUID • Particles of liquids are tightly packed, but are far enough apart to slide over one another. • Liquids have an indefinite shape and a definite volume. Heat

  36. STATES OF MATTERGAS • Particles of gases are very far apart and move freely. • Gases have an indefinite shape and an indefinite volume. Heat

  37. PHASE CHANGES

  38. PHASE CHANGES

  39. Melting and Freezing •Melting pointisthetemperature whenamatterisstartingtomelt. Example:meltingpointoficeis0°C •Freezing pointisthetemperature 14 whenamatterisstartingtofreeze. Example:freezingpointofwateris 0°C Meltingpoint=Freezingpoint Melting point

  40. MeltingheatandFreezingheat 15 Theamountofheatabsorbedbyevery1kgofmatterfor meltingatitsmeltingpointiscalledMeltingheat(L). Theamountofheatreleasedby1kgofmatterforfreezingat itsfreezingpointiscalledFreezingheat(L). SIUnitofMeltingHeatandFreezingHeat:J/kg

  41. 16 AMOUNTOFHEAT(Q)RECEIVEDORRELEASEDBYAMATTER WHENITMELTSORFREEZES Where: Q=amountofHeatreceivedorreleased(J) m=massofmatter(kg) L=MeltingheatorFreezingHeat(J/kg)

  42. boilingandcondensationPoint Boilingpointisthetemperaturewhenamatteris startingtoboils. Example:boilingpointofwateris100ºC Condensationpointisthetemperaturewhena matterisstartingtocondenses. Bolingpoint=Condensationpoint Boilingpointofaliquidisaffectedbyair pressure 17 •Thegreatertheairpressurethegreaterthe boilingpointofliquid •Onthesealevel,atairpressureof1atm,the boilingpointofwateris100ºC. •Athigherplace,theairpressureisdecrease andboilingpointofwaterisalsodecrease. Boiling point

  43. Vaporingheatandcondensationheat 18 Theamountofheatabsorbedbyevery1kgofmatterfor vaporizeatitsboilingpointiscalledvapouringheat(U). Theamountofheatreleasedby1kgofmatterforcondense atitscondensationpointiscalledcondensationheat(U). SIUnitofVapouringHeatofCondensationHeat:J/kg

  44. 19 AMOUNTOFHEAT(Q)RECEIVEDORRELEASEDBYAMATTER WHENITEVAPORATESORCONDENSES Where: Q=amountofHeatreceivedorreleased(J) m=massofmatter(kg) L=VaporingHeatorCondensationHeat(J/kg)

  45. 20

  46. Differencesbetween evaporationandboiling Point 21

  47. Several Aspect That Speed up Evaporation 22 •Heating –Whenweheatedliquid,themoleculesnearthesurfacevibrate faster,whichenablethemtoreleasefromliquid’ssurface •Blowingairthroughtheliquid’ssurface –Ifweblowairthroughthesurfaceofahotwater,theairnearthe watersurfacewouldcarrythewater’smoleculesatthesurface. •Extendingthesurface –Tomakehotteainacupcoldfaster,youshouldpouronasaucer, becausethesurfaceareaofthesaucerislargerthanonthecup, sothemoleculeshavemorechancestoleavethewatersurface •Decreasingthepressureonthesurface –Ifthepressuredecreasing,thespacebetweenairmoleculesnear thesurfacebecomelooseranditmakeeasierforthemoleculesof watertofilltheemptyspaceamongthemoleculesofair.

  48. Quick Quiz! 23 1.Ificemelting,thestatechangefrom….to… 2.Formelting,ice….heatenergy 3.Duringicemelted,temperatureis…..anditis called… 4.Amountofheatenergyusedtomeltyoucan calculatewiththeformula 5.Duringthewaterboil,thetemperatureis…and itiscalled… 6.Duringthewaterboil,thestatechangefrom… become…andiscalled… 7.Duringevaporationthewater……heatenergy. 8.Quantityheatenergyusedtoevaporationcan calculatebytheformula…

  49. Example 24 1.Calculatethequantityofheatrequiredtomelt3kgofice on0ºC!(L=3.36x105J/kg) Known:m=3kg L=3.36x105J/kg=336,000J/kg Question:Q? Answer: Q=mxL Q=3kgx336,000J/kg Q=1,008,000J=1,008kJ

  50. Example 25 2.Calculatethequantityofheatrequiredtochange500grams ofwateratatemperatureof100ºCintowatervaporata temperatureof100ºC!(U=2270kJ/kg) Known:m=500grams=0.5kg U=2270kJ/kg Question:Q? Answer: Q=mxU Q=0.5kgx2,270kJ/kg Q=1,135kJ Q=1,135,000J

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