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HEAT11Heat is a form of energy (can be used to do work )

Heat cause objects to become hot

Heat energy is also called as thermal energy.

22State sources of heat33sun 4

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5Uses of Heat energy in our daily lifeTo cook food and boil water for drinking.To dry clothes and hair.To drive steam generators that produce electricity.

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6To evaporate sea water to produce salt and to dry tea leaves. To warm our body during cold weather. To sterilise instruments.

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788What is heat?

What is temperature?

What the differences between heat and temperature?99HEAT is the amount of energy that is put into a body to warm it up.1010Temperature is used to describe how hot something is.

It measures the degree of hotness or coldness of the body.1111Differences between HEAT & TEMPERATURE.121213HEATTEMPERATURE- Form of energy. Hotness of an object.- Measure of the degree of hotness @ coldness- Object absorbs heat become hotter, loses heat become colder- Used thermometer to measure temperature- Unit ~ joule (J)Unit ~ celsius (C) & kelvins (K)13Relationship between temperature and heatTemperature is used to measure the amount of heat in the body by using thermometer. 1414Complete the sentences using the information given below.1 Heat is a form of .2 The the mass of a substance, the will be its heat content.3 Heat flows from a section to a section.4 is a measurement of degree of hotness.5 A hot substance has a temperature while a cold substance has atemperature.6 The heat content of a substance depends on the and of thesubstance.151516167.2 THE EFFECT OF HEAT FLOW ON MATTER17

17Heat is the flow of energy from warmer objects to cooler objects (difference in temperature)

An object expends when heated and contracts when cooled.

1818Expands~ When an object heated, the particles move faster and further apart. The volume of the object increases when heated.

Contracts~ When an object loses heat energy, its cooled down, the particles move slowly and come close together. The volume of the object decreases & cools down.

1919The effect of heat on solidsActivity 1

What happened to the metal ball Before heating :After heating :After cooling :20202. What happened to the size (volume) of the metal ball when it was heated?it increased

3. What happened to the size (volume) of the metal ball when it was cooled?it decreased

Conclusion:i) the metal ball ________and ________ its size when heated.ii)the metal ball ________ and _______ its size when cooled21expandsincreasescontractsdecreases21Arrangement of particle in solids22coldhot22Arrangement of particle in solids23coldhot23The effect of heat on liquidsActivity 2

What happened to the reading of thermometer when thermometer was :i) held in between palms? the reading of thermometer up/rise

ii)placed between the ice cubes? the reading of thermometer fell24242. What happened to the mercury in the thermometer when it was heated by body heat?it expanded

3. What happened to the mercury in the thermometer when it was cooled?it contract

Conclusion:A liquid _________ when heated and ________ when cooled.25expandscontracts25Arrangement of particle in liquids26coldhot26Arrangement of particle in liquids.27coldhot27The effect of heat on gasesActivity 3

1. What happened to the dented ping-pong ball when :i) in the cold water :contractsii)in the hot water :expandsConclusion :gas _________ when heated and _______ when cooled28expandscontracts28Arrangement of particle in gases.29coldhot29Arrangement of particle in gases.30coldhot303131HEAT FLOW32Heat can travel by three ways :conductionconvectionradiation

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conductionConduction is the flow of heat through solids.

In this process particles in the medium do not flow, only vibrate within a fixed area.

Heat is transferred from the hotter end of the object to the cooler end.

Metals are very good conductor of heat

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convectionConvection is the transfer of heat from one part of a fluid (substances which can flow) to another by the circulating movement of that heated fluid.

Liquid and gases are fluid.

The circulating movement is called a convection.3434radiationRadiation is a process of heat transfer that does not require a medium.Radiation can take place in a vacuum.Properties of radiant heat:-Travels as electromagnetic waves -Travels at the speed of light-Travels in a straight line-Travels through a vacuum-Can be absorbed or reflected

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RADIATIONThere are no particles betweenthe Sun and the Earth so itCANNOT travel by conduction orby convection.WHY??3637

37COMPARING CONDUCTION, CONVECTION AND RADIATION38

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