202442700 Science Form1 Chapter 7

7/25/2019 202442700 Science Form1 Chapter 7

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Chapter 7: HEAT


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1) Heat is a form of energy. The SI unit isjoule,

!) "hen heat energy is supplie# to a su$stan%e,the temperatureof the su$stan%e &ill rise.

') Heat (o&s from a hotter to a %ol#er pla%e.This pro%ess of heat transfer &ill stop &hen the

temperature of the ! pla%es $e%ome the same.) Sour%es of heat:

7.1 Heat as a form of energy

Sources ofheat

Burning%an

pro#u%eheat

! o$je%tshitting

ea%h other%an

pro#u%e

heat

Rubbingorfriction

$et&een !o$je%ts %an

pro#u%e

heat


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*) +seful of heat:

a) #rying $) ironing %) %ooing #) eeping

&arm

Temperature

1) Temperature is the measure of the #egree ofhotness or %ol#ness of an o$je%t.

!) A thermometer is use# to measuretemperature. The SI unit of temperature is theel-in, /). Ho&e-er, the %ommonly use# unit is#egree Celsius 0C).

') Hotsu$stan%es ha-e high temperatures &hereas%ol#su$stan%es ha-e lo& temperatures.


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) The #ieren%e $et&een heat an# temperature:

Heat

A form of energy

Can #o &or

SI unit 2 oule )

TemperatureA measure of the

hotness or%ol#ness of an

o$je%t

Cannot #o &or

SI unit 2 el-in /)


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*) ' types of thermometers:

Type ofthermometer

Mercuryin

glass la$oratorythermometer

Clini%althermometer

Alcoholinglassthermometer

3angetemperature

4100

C an# 1100C

'* 0C an# ! 0C

4117 0C an# 750C

+se

6easures

temperature&hen #oingeperiments

6easures $o#ytemperature

6easures -erylo&temperatures


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Is heate#8arti%les absorb

heat

8arti%les re%ei-eenergy an# move

faster

The #istan%e$et&een the

parti%les increase

The volumeof thematter increases

The matterexpands

Is %oole#8arti%les release

heat

The parti%les loseenergy an# mo-e

more slowly

The #istan%e$et&een the parti%les

decreases

The volumeof thematter decreases

The mattercontracts

6atter7.! The eectof heat ow

on matter


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xpansion and !ontraction "Solids#

1) A soli# epan#s &hen it is heate#. It %ontra%t&hen it is %oole#.

!)The epansion of soli# %an $e sho&n $y a metalball$

') 9ierent metals epan# at #ierent rates: Aluminium

Brassexpansionincreases !opper

%ron

%nvar


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) 9ierent metals epan# uneually &hen heate# tothe same temperature. This %an $e eplaine# $y

heating bimetallic strip.

;rass

Iron

Heate#

< "hen heate#, sho&ing that brass epan#s morethan iron

Heate#

< "hen heate#, sho&ing that aluminiumepan#smore than copper

Aluminium

Copper


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xpansion and !ontraction "&i'uids#

1) A liui# epan#s &hen it is heate#. It %ontra%t&hen it is %oole#.

!) 9ierent liui#s epan#s an# %ontra%t at#ieren%e rates

Ben(ene

Alcoholincreases )ater

expand

Mercury


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xpansion and !ontraction "gases#

1) =ases epan#s &hen it is heate# an# %ontra%t &hen %oole#.

!) 9ierent gases epan#s at the same rate.

Transfer of *eat

1) Heat %an $e transferre# from a hot to a %ol# pla%e $y thepro%ess of :

a) Con#u%tion

$) Con-e%tion

%) 3a#iation


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!+,-.!T%+,

1) !onductionis the transfer of heat energy $et&eenneighboring molecules in a su$stan%e. It taes pla%e

from a region of higher temperature "hot# to a region oflower temperature "cold#$

!) "hen one part of an o$je%t is heate#, its get hot. Theparti%les there gain heat energy maing them -i$rate

stronger. They then collide an# pass some heat energyto the neigh$ouring parti%les.

Iron ro#

Heat transfer


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!+,/!T%+,

1) !onvection is the transfer of heat in (ui#s liui#s an#gases) %arrie# out $y mo-ing parti%les$

!) *ot(ui#s$e%ome less dense an# mo-e up&ar#s.

!old(ui#sthat are densermo-e #o&nto repla%e thehot (ui#s.

') A convection current is pro#u%e#.

Con-e%tion in liui#


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!onvection


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RA-%AT%+,

1) Radiation is the transfer of heat &ithout in-ol-ing ame#ium$

!) Radiation %an tae pla%e through air space or a-a%uum.

') 3a#iation heat mo-es at the speed of light.

) 3a#iation heat %an $e absorbedor reected


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Con#u%tion

Soli#

>o

Slo&

Heat istransfer from

parti%le toparti%lethrough

vibration

Con-e%tion

?lui# liui#or gas)

>o

?aster than%on#u%tion

Heat is$rought $ythe heate#

parti%les thatmo-e

up&ar#s

3a#iation

Soli#, liui# orgas @ no

me#iumes

Bery fast

Heat mo-es inthe form of&a-es in a

straight line

omparison between conduction0convection and radiation

6e#ium

Tae pla%e inBa%uum

Spee#

"ay heat istransfer


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*eat 1low in ,atural 2henomena

1) A>9 ;3EEDE

1) an# $reee $lo& #uring the night$3# At night , the lan# loses heat faster than the sea.

') The lan# $e%ome %ooler than the sea.

) The warm air a$o-e the surfa%e of the sea less #ense)rises. The cool air a$o-e the lan# #enser) (o& to thesea


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!) SEA ;3EEDE

1) Sea $reee $lo& #uring the day$

3# 9uring the #ay, the lan# heats up faster than the sea.

') The air on surfa%e of the lan# $e%ome warmless#ense) an# rises .

) The cooler air o-er the sea #enser) (o&s in to tae

pla%e of the warmair.


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HEAT CF>9+CTF3

1) Su$stan%e that %on#u%t heat are %alle# heat%on#u%tor.

!) Some su$stan%es %on#u%t heat rea#ily G goo# heat%on#u%tor)

') All metal su%h as iron, magnesium, aluminiuman# in%are goo# %on#u%tors of heat.

Copper

Aluminium ;rass $est%on#u%tor

Din%Tin Iron ea#


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+ses of heat %on#u%tors

o4ing utensil " 4ettles0 pots0 pans# areade from metals$ 1ood can be coo4edic4ly or water can be boiled 'uic4ly$

Mercury in the bulb expandsand contractseasily$

5#3#

Thermometer!oo4ing utensils

lectric iron

6#The bottom of an electric iron ismade up of metals so that it can

heat up 'uic4ly


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HEAT I>S+ATF3

1) Su$stan%e that %on#u%t heat poorly are %alle#

insulators!) >on4metal su%h as glass, &oo#, %or, air, &ater an#

&oolare insulators.

') ?lui#s liui#, gas) are poor %on#u%tors of heat.

.ses of heat insulators.

5# *andlesof 4ettle

*andles of 4ettles0 irons and

coo4ing utensils such as pots andfrying pan are made of woodor plastic


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Appli%ation of the prin%iple of convectionin #aily life

1) /entilation of building

a) The hot air in the $uil#ing &ill (o& out through the-entilation holes at the top. The %ol# air enters through theholes &in#o&s@#oor) on the lo&er part.

!) Refrigeratora) Col# air from the freeer %ompartment at the top mo-es#o&n to the lo&er part of the refrigerators. The hot air ismo-e# up.

') The cooling system in a carra#iator of the %ar)

a) The &ater aroun# the engine $e%omes hot &hen theengine mo-es. Hot &ater (o&s up through the ra#iatoran# gets %oole#. The %ol# &ater mo-es #o&n an# (o&s$a% aroun# the engine.


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1) Matter exists in solids, liquids and gases. Matter can change from one

state to another.

Eg: Solidcan be change to a liquidby heating. (heat absorb)

A liquidstate can be change to a solidby cooling. (heat release)

7.' Ee%t of Heat on 6atter

1ree(in

g

Melti

ng

vaporatio

n7

boilin

g!ond

ensati

on

Sublimation

Sublimation

&i'uid

8asSolid


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2rocess

Con#ensation

6elting

?reeing

E-aporation@;oiling

Su$limation

Su$limation

!hange instate

=as4liui#

Soli#4liui#

iui#4soli#

iui# 4 gas

Soli#4gas

=as4soli#

Absorb7

releaseheat

3elease heat

A$sor$ heat

3elease heat

A$sor$ heat

A$sor$ heat

3elease heat

matter$


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6elting pg 11!411')

?reeing pg 11')

;oiling pg 11, 1stparagraph)

Con#ensation pg 11, !n#paragraph)E-aporation pg 11*) G The pro%ess of %hanging a

li'uidto a gas.

Su$limation pg 11)

>ote in tet$oo)


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CHA>=E I> STATE F? 6ATTE3 9AI I?E

1) "et %lothes G &hen &et %lothes #ry in the sun, the &ater

in the %lothes e-aporate.!) 8u##les of &ater 4 After a rain, there are pu##les of

&ater on the groun#. "hen the sun %ome out,these pu##les e-aporate.

') I%e %u$es G I%e %u$e %an $e prepare# $y freeing&aterun#er lo& temperature.

) 6oth $all G 6oth $all $e%ome smaller $e%ause of thepro%ess of su$limation.

*) 3ain&ater 4 "ater -apours in %lou#s %on#enseto formrain&ater.


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8age 11541141!04 tet$oo)

8age 114 S%ien%e pro%ess sills)

7. : Appli%ation of epansion an#%ontra%tion of matter


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=oo#heat

a$sor$er

9aran##ull

surfa%e

;a# heata$sor$er

"hitean#

shiny

surfa%e

=oo#gi-ingout

emits)heat

;a#gi-ingout

emits)heat

7.* : A$sor$ing an# =i-ing FutHeat

9aran##ull

surfa%e

"hitean#

shiny

surfa%e


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202442700 Science Form1 Chapter 7

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