Haba

What is Heat?Suatu bentuk tenaga - kerana ia boleh menggerakkan benda - E.g: Makes a hot air balloon rise.- Steam engines

Diukur dalam unit JOULES (J)

HabaHaba adalah bentuk tenaga yang boleh mengalir dari kawasan panas ke kawasan sejuk

Haba boleh bertukar bentukProses fotosintesis ( Tumbuhan membuat makanan)Tenaga cahaya & haba Tenaga kimia

Stesen Jana kuasa (Pembakaran minyak dan gas)Tenaga haba Tenaga kinetik Tenaga elektrik

Bagaimana haba dihasilkan?Pergerakan zarah-zarah menghasilkan haba.Haba dapat dihasilkan melalui geseran, pembakaran bahan api, tenaga elektrik dan sebagainya.Haba menyebabkan pengembangan dan pengecutan pepejal, cecair dan gas.

Haba Vs SuhuThe temperature of an object tells us how HOT it isUkuran darjah kepanasan atau kesejukkan suatu objek.

Measured in degrees Celsius - C

Haba Vs SuhuIt 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

Pengaliran habaMengalir dari kawasan yang panas ke kawasan yang sejuk.Objek panas dalam bilik akan menjadi sejuk ke takat suhu bilik.e.g: air kopiObjek sejuk dalam bilik akan dipanaskan ke takat suhu bilik. e.g: butter, ice

What do you think?

Pengaliran haba3 caraKonduksi/ ConductionPerolakan/ ConvectionSinaran/ Radiation

Konduksi/ ConductionPengaliran haba dari kawasan panas ke kawasan sejuk pada suatu pepejal.Zarah-zarah pada satu hujung rod pepejal yang dipanaskan memperolehi tenaga haba dan bergetar dengan lebih cepat dan berlanggar dengan zarah-zarah bersebelahan. Tenaga haba dipindahkan kepada zarah-zarah bersebelahan secara berterusan dan akhirnya ke seluruh rod logam.

Konduksi/ ConductionWhen 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

Why does metal feel colder than wood, if they are both at the same temperature?Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

Perolakan/ ConvectionWhat 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.

Perolakan/ ConvectionProses pengaliran haba melalui bendalir (cecair dan gas) akibat gerakan bendalir dari kawasan yang lebih panas ke kawasan yang kurang panas.

Perolakan/ Convection

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

Perolakan/ ConvectionHot water risesCooler water sinksConvection current Cools at the surface

Perolakan/ ConvectionWhere is the cooling compartment put in a fridge?

Cooling compartmentIt is put at the top, because cool air sinks, so it cools the food on the way down.It is warmer at the bottom, so this warmer air rises and a convection current is set up.

Convection questionsWhy are boilers placed beneath hot water tanks in peoples homes?

Hot water rises.So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.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.

How does heat energy get from the Sun to the Earth?

There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. ?RADIATION

Sinaran/ RadiationProses pemindahan haba daripada suatu sumber haba ke kawasan persekitarannya tanpa mediumMengalir ke semua arah daripada objek yang panas.Semakin panas objek, semakin banyak haba yang mengalir melalui sinaran.Does the surface affect the way heat is radiated?

Radiation Think Pair-ShareRadiation travels in straight linesTrue/FalseRadiation can travel through a vacuumTrue/FalseRadiation requires particles to travelTrue/FalseRadiation travels at the speed of lightTrue/False

Radiation questionsWhy 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.

Konduktor haba dan penebat habaKonduktor haba bahan yang membenarkan haba melaluinya dengan mudah. e.g: most metalsPenebat haba bahan yang menghalang haba mengalir melaluinya. e.g: wood, plastic, glass

Why do many sauce pans have plastic handles?

Konduktor haba Vs Penebat haba

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

Pelbagai Kegunaan konduktor dan penebat dalam kehidupan harianBincangkanPemanas pada dasar cerek elektrikPeriuk dan kualiSeterika elektrikRadiator keretaMerkuriKotak ais

Pelbagai Kegunaan konduktor dan penebat dalam kehidupan harian Rajah di sebelah menunjukkan struktur binaan sebuah kelalang termos. Struktur binaan kelalang termos bertujuan untuk mengurangkan kehilangan haba. Bincangkan.

Penyerap dan Pembebas haba yang BaikKeupayaan suatu objek untuk menyerap dan membebaskan haba dipengaruhi oleh ciri permukaan objek (jenis dan warna)Permukaan yang gelap dan kusam menyerap dan membebaskan haba lebih baik daripada objek putih dan berkilat

Emission experimentFour containers were filled with warm water. Which container would have the warmest water after ten minutes?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.shiny metalradiationdull blackemitting

Absorption experimentFour containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes?The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation.dull blackradiationshiny metalabsorbing

EmittersHotter objects emit (give out) heatDifferent surfaces emit heat at different speedsA dull black surfaces loses energy more quickly it is a good radiatorA bright shiny or white surface is a poor radiatorMarathon runners need to keep warm at the end of races, covering in shiny blankets reduces radiation and therefore heat loss.

Emitters of heatBright shiny can Poor radiatorDull black can Good Radiator

AbsorbersCooler objects absorb (take in) heatSubstances absorb heat at different speedsDull, black surfaces absorb heat quicklyBright, shiny surfaces absorb heat slowlyIn hot countries, people wear bright white clothes and paint their houses white to reduce absorption of energy from the sun.Petrol storage tanks sprayed silver to reflect suns rays

AbsorbersShiny, bright can Poor absorberDull black can Good absorber

Revision1. Which of the following is not a method of heat transfer? A.RadiationB.InsulationC.ConductionD.Convection

Revision1. Which of the following is not a method of heat transfer? A.RadiationB.InsulationC.ConductionD.Convection

2. In which of the following are the particles closest together?A.SolidB.LiquidC.GasD.Fluid

2. In which of the following are the particles closest together?A.SolidB.LiquidC.GasD.Fluid

3. How does heat energy reach the Earth from the Sun?A.RadiationB.ConductionC.ConvectionD.Insulation

3. How does heat energy reach the Earth from the Sun?A.RadiationB.ConductionC.ConvectionD.Insulation

4. Which is the best surface for reflecting heat radiation?A.Shiny whiteB.Dull whiteC.Shiny blackD.Dull black

4. Which is the best surface for reflecting heat radiation?A.Shiny whiteB.Dull whiteC.Shiny blackD.Dull black

5. Which is the best surface for absorbing heat radiation?A.Shiny whiteB.Dull whiteC.Shiny blackD.Dull black

5. Which is the best surface for absorbing heat radiation?A.Shiny whiteB.Dull whiteC.Shiny blackD.Dull black

Key Words

HeatRadiationConvectionConductionColdInsulatorConductorTemperatureEmitAbsorbTransfer

***********************************************