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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

HEAT

OBJECTIVES

MATTER

EVALUATION


Objectives

Standardcompetencyand BasicCompetency

HEAT

StandardCompetency

:

Comprehendingstatesofmatter andits

change

BasicCompetency

  • Describeroleofheatinchanges

  • statesofmatterand temperature’ssubstance

  • alsoits applicationindailylife


Objectives

3

  • BLack’s Principle

  • Heat and Change State

  • Heat and Change Temperature

  • What is HEAT?


Heat and temperature

HEAT AND TEMPERATURE

Areheatenergyandtemperaturejustthesamething?

No!Let'sgetthisclear:

Heatistheenergystoredinsidesomething.

Temperatureisameasurementofhowhotorcold

somethingis.

Anobject'stemperaturedoesn'ttellushowmuchheat

energyithas.


Objectives

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


Objectives

What Is Heat?

6

Heatenergyisthetotalenergyofparticlescomposinga

matter.

Heatisoneformofenergywhichisflowingfromanobjectwith

highertemperaturetoanotherobjectwithlowertemperature

TheunitofHeatisJoule(J)

Heatisalsoexpressedinunitsofcalories.

Onecaloriedefinedastheamountofheatneededtoheat1

gramofwateruntilitstemperatureincreasing1C°.

1calorie=4.2joules

1joule=0.24calories


Heat transfer

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


What do you think

What do you think?


Forms of heat transfer

Forms of Heat Transfer


Radiation

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

?


Radiation1

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?


What colour should we paint radiators which colour is better to wear on a sunny day black or white

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.


Objectives

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


Radiation think pair share

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


Radiation questions

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.


Conduction

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


Conduction1

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


Conductors insulators

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?


Conduction v insulation

Conduction V Insulation


Conductor or insulator

Conductor or Insulator?

  • Wood?

  • Aluminium?

  • Plastic?

  • Glass?

  • Iron?

  • Polystyrene?

  • Copper?

  • Cardboard?


Convection

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.


Convection1

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


Convection2

Convection

Cools at the surface

Convection current

Cooler water sinks

Hot water rises


Convection3

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.


Should a radiator be called a radiator

Should a radiator be called a radiator?


Convection questions

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.


Objectives

Heat and the change

7

oftemperature

Notallsubstanceshavethesameabilityinabsorbing

heat.

Theabilitytoabsorbheatdeterminedbythenatureof

asubstancecalledspecifichetcapacity.

SpecificHeatCapacity(c)

Thespecificheatcapacityofasubstanceis

definedastheheatrequiredtoraisingthe

temperatureof1kgofthesubstanceby1°C.

Theunitofspecificheatcapacityisjouleperkilogram

perCelsiusdegree(J/kgC°)


Objectives

Specifik Heat Capacity

8

Thisprovedthatheatneededtoraisethe

temperatureof1C°alcoholissmaller

thantheheatneededtoraisewater

temperatureat1C°.Thatis,alcohol heat

faster than water.


Objectives

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°)


Objectives

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


Objectives

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=


Objectives

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!


Objectives

Heat and the change State of Matter

13

•Whenamatterchangeitsstate,the

temperature does not increasealthoughthe

heatiscontinuouslygiven.

•Theheatisusedtochangingthestateofmatter.

•Theheatusedforchangingthestateofmatteris

calledLatentheat.


States of matter solids

STATES OF MATTERSOLIDS

  • Particles of solids are tightly packed, vibrating about a fixed position.

  • Solids have a definite shape and a definite volume.

Heat


States of matter liquid

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


States of matter gas

STATES OF MATTERGAS

  • Particles of gases are very far apart and move freely.

  • Gases have an indefinite shape and an indefinite volume.

Heat


Phase changes

PHASE CHANGES


Phase changes1

PHASE CHANGES


Objectives

Melting and Freezing

•Melting pointisthetemperature

whenamatterisstartingtomelt.

Example:meltingpointoficeis0°C

•Freezing pointisthetemperature

14

whenamatterisstartingtofreeze.

Example:freezingpointofwateris 0°C

Meltingpoint=Freezingpoint

Melting

point


Objectives

MeltingheatandFreezingheat

15

Theamountofheatabsorbedbyevery1kgofmatterfor

meltingatitsmeltingpointiscalledMeltingheat(L).

Theamountofheatreleasedby1kgofmatterforfreezingat

itsfreezingpointiscalledFreezingheat(L).

SIUnitofMeltingHeatandFreezingHeat:J/kg


Objectives

16

AMOUNTOFHEAT(Q)RECEIVEDORRELEASEDBYAMATTER

WHENITMELTSORFREEZES

Where:

Q=amountofHeatreceivedorreleased(J)

m=massofmatter(kg)

L=MeltingheatorFreezingHeat(J/kg)


Objectives

boilingandcondensationPoint

Boilingpointisthetemperaturewhenamatteris

startingtoboils.

Example:boilingpointofwateris100ºC

Condensationpointisthetemperaturewhena

matterisstartingtocondenses.

Bolingpoint=Condensationpoint

Boilingpointofaliquidisaffectedbyair

pressure

17

•Thegreatertheairpressurethegreaterthe

boilingpointofliquid

•Onthesealevel,atairpressureof1atm,the

boilingpointofwateris100ºC.

•Athigherplace,theairpressureisdecrease

andboilingpointofwaterisalsodecrease.

Boiling

point


Objectives

Vaporingheatandcondensationheat

18

Theamountofheatabsorbedbyevery1kgofmatterfor

vaporizeatitsboilingpointiscalledvapouringheat(U).

Theamountofheatreleasedby1kgofmatterforcondense

atitscondensationpointiscalledcondensationheat(U).

SIUnitofVapouringHeatofCondensationHeat:J/kg


Objectives

19

AMOUNTOFHEAT(Q)RECEIVEDORRELEASEDBYAMATTER

WHENITEVAPORATESORCONDENSES

Where:

Q=amountofHeatreceivedorreleased(J)

m=massofmatter(kg)

L=VaporingHeatorCondensationHeat(J/kg)


Objectives

20


Objectives

Differencesbetween

evaporationandboiling Point

21


Objectives

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.


Objectives

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…


Objectives

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


Objectives

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


Objectives

Example

26

3.Calculatetheheatrequiredtochange1kgofwaterat

temperatureof80ºCinto1kgofwatervaporata

temperatureof100ºC(specificheatofwateris4200J/kgºC

andvapouringheatofwateris2270kJ/kg)

Temperature

Q2

Known:m=1kg

∆T=(100-80)Cº=20Cº100ºC

c=4200J/kgCº

U=2270kJ/kg=2,270,000J/kg80ºC

Question:Qtotal

Answer:

Q1

Heat(J)

Q1=mxcx∆T

Q2=mxU

Qtotal=Q1+Q2

=(mxcx∆T)+(mxU)

=(1kgx4200J/kgCºx20Cº)+(1kgx2,270,000J/kg)

=84,000J+2,270,000J=2,354,000J


Objectives

Example

27

4.Icecubehasmass100gramat0ºC.Ifitheateduntil20ºC

theallicebecomewater.Howmuchheatenergyabsorb?

(meltingheatofice=80cal/g;specificheatofwater1cal/gcº)

Known:m=100g

∆T=(20-0)Cº=20Cº

L=80cal/g

c=1cal/gCº

Question:Qtotal

Answer:

Q1=mxL

Q2=mxcx∆T

Qtotal=Q1+Q2

=(mxL)+(mxcx∆T)

=(100gx80cal/g)+(100gx1cal/gCºx20Cº)

=8,000cal+2000cal

=10,000cal


Objectives

Exercise of Heat

28

1.Calculateheatneededtochange100gramoficeat–30°Cinto

watervaporat120°C.

cice=2100J/kg°C

cwater=4200J/kg°C

cwatervapor=2010J/kg°C

Lice=336,000J/kg

Uwater=2,270,000J/kg


Objectives

Who Is Black?

29

•JosephBlack(16April1728–6

December1799)wasaScottish

physician,knownforhis

discoveriesoflatentheat,specific

heat,andcarbondioxide.


Objectives

The Black Principle

30

•Whentwosubstancesormorearemixed,the

amountofheatreleasedbythesubstance

withhighertemperatureisequaltothe

amountofheatabsorbedbythesubstance

withlowertemperature.

Q

=Qreceived

released


Objectives

Example

31

100gramsofhotwaterat40°Cismixedwith200gramsofwaterat

10°C.Whatisthefinaltemperatureofthismixture?

Given:m1=100gramsT1=40°C

T1

T2=10°C

m2=200grams

Question:Tf(FinalTemperature)

Solution

∆T1=T1-Tf

Tf

Qreleased=Qreceived

m1.cwater.∆T1=m2.cwater.∆T2

m1.cwater.(T1–Tf)=m2.cwater.(Tf–T2)

m1.(T1–Tf)=m2.(Tf–T2)

100g(40–Tf)=200g.(Tf–10)

4000–100Tf=200Tf–2000

4000+2000=200Tf+100Tf

6000=300Tf

Tf=6000/300=20°C

∆T2=Tf–T2

T2


Objectives

Exercise Of Black Principle

32

1.ThevolumeofwateringlassBishalfofthevolumeof

wateringlassA.ThewateristhenmixedinglassC.The

finaltemperatureofthewateringlassCis…

2.½kgofhotwaterat80°Cismixedwith2kgofcold

water.Whatisthetemperatureofcoldwaterifthefinal

temperatureofmixtureis24°C?


Objectives

THANKS!


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