chapter-4-heat (answer).pdf

8/17/2019 Chapter-4-Heat (Answer).pdf

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JPN Pahang Physics Module Form 4

Teacher’s Guide Chapter 4: Heat

4.1 : UNDERSTANDING THERMAL EQUILIBRIUM

By the end of this subtopic, you will be able to

• Explain thermal equilibrium

• Explain how a liquid-in glass thermometer works

1. The net heat will flow from to B until the temperature of is the ! same, zero as the

temperature of B. "n this situation, the two bodies are said to ha#e reached thermal

equilibrium.

$. %hen thermal equilibrium is reached, the net rate of heat flow between the two bodies is

!zero, equal

&. There is no net flow of heat between two ob'ects that are in thermal equilibrium. Two ob'ects

in thermal equilibrium ha#e the same temperature.

4. T!e l"qu"# use# "$ %lass &!ermome&er s!oul#

(a) Be easily seen

(b) Expand and contract rapidly over a wide range of temperature

(c) Not stick to the glass wall of the capillary tube

(. )ist the characteristic of mercury

(a) Opaque liquid

(b) oes not stick to the glass

(c) Expands uniformly when heated

!d* !ree"ing point #$%&'

!e* Boiling point $ &'

1

Thermal equilibrium+eseimbangan terma

'HA(TER 4: HEAT

aster . rate of energy transfer

Ho&

o)*e+&

'ol#

o)*e+&

lower rate of energy transfer

Equi#alent to Equi#alent to

/o net heat transfer

B


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0. ! Hea&, Temera&ure * is a form of energy. "t flows from a hot body to a cold body.

. The " unit for - !ea& , &emera&ure is 2oule, 2.

3. ! 4ea& , Temera&ure * is the degree of hotness of a body

5. The " unit for !!ea& , &emera&ure* is el#in, .

16. Loer /"0e# o"$& -l 7 ice point + the temperature of pure melting ice7668

11. Uer /"0e# o"$&- l 17steam point+ the temperature of steam from water that is boiling

under standard atmospheric pressure 716668

E0er+"se 4.1

Se+&"o$ A: '!oose &!e )es& a$ser

1. The figure shows two metal blocks.

%hich the following statement is false9

. : and ; are in thermal contact

B* + and , are in thermal

equilibrium

8. Energy is transferred from : to ;


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B. 0sing a capillary tube with a

narrower bore.

8. @sing a longer capillary tube


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&. The distance between 668 and 16668 is $3.6 cm. %hen the thermometer is put into a beaker

of water, the length of mercury column is $>.(cm abo#e the lower fixed point. %hat is the

temperature of the water9

Temera&ure, 3 l3 5 l 0 1'

l1 5 l

3 64.8 0 1'

6<

3


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SE'TI=N ': S&ru+&ure# Ques&"o$s

1. )uqman uses an aluminium can, a drinking straw and some plasticine to make a simple

thermometer as shown in figure below. 4e pours a liquid with linear expansion into the can.

!a* uggest a kind of liquid that expands linearly. !1m*

.

!b* 4e chooses two fixed points of 8elsius scale to calibrate his thermometer. tate them.

!$m*

!c* "f the measurement length of the liquid inside the straw at the temperature of the lower

fixed point and the upper fixed point are (cm and 10 cm respecti#ely, find the length of

the liquid at 3$.(68.

!d* %hy should he use a drinking straw of small diameter9

!e* %hat kind of action should he take if he wants to increase the sensiti#ity of his

thermometer9

(

-lkohol

.63 cm

5ower fixed point 6 free"ing point of water*

0pper fixed point 6 boiling point of water

1o increases the sensitivity of the thermometer

0se a copper can instead of the aluminum can because it is a better thermal

conductor


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$. %hat do you mean by heat and temperature9

....

>.$ : UNDERSTANDING S(E'I>I' HEAT 'A(A'IT?


•


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(. 4igh specific heat capacity absorb a large amount of heat with only a small temperature

increase such as plastics.

0. 8on#ersion of energy

. pplications of pecific 4eat 8apacity

Explain the meaning of abo#e application of specific heat capacity+

-a a&er as a +oola$& "$ a +ar e$%"$e

!i* %ater is a good example of substance with a high specific capacity. "t is used as a

cooling agent to pre#ent o#erheating of the engine .Therefore, water acts as a

heat reser#oir as it can absorb a great amount of heat before it boils.

Electrical energy 4eat energy

Pt mc∆!

4eater

:ower : Electrical energy

+otential energy

3inetic energy

Hb'ect falls from

high position

Co#ing ob'ect stopped

due to friction

4eat energy

m h mc∆!

4eat energy

" m#$ mc∆!

mall #alue of c Big #alue of cTwo ob'ect of

equal mass

Equal rate ofheat supplied

aster increase

in temperature

lower increase

in temperature


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!b* 4ousehold apparatus and utensils

...

...

...

...

!c* ea bree=e

!d* )and bree=e

3

1. metal has a low specific heat capacity.

$. "ts temperature increases easily when heated.

&. The food or water can be heated faster.>. This is because only a little amount of heat is needed to heat the metal,

therefore more heat is transferred to the food.

(. Examples + pot, frying-pan, filaments of kettles and others utensils

Think about it+ %hy the handles of utensils made of materials of high c

1. during a day, the land and the sea recei#e thesame amount of heat from the sun.

$. The land has a lower c, and the temperature

higher than the sea water.&. The air abo#e the land to be hotter and flows up

and the cool air from the sea flows towards the

land.>. The mo#ement of air cause wind to blow from

the sea and produced a sea bree=e.

1. %t night& the land and the sea release heat to

atmosphere'$' The sea (ater has a higher c& and release moreheat'

)' The air abo#e the sea (ater to be hotter and

*lo(s up and the cool air *rom the land *lo(sto(ards the sea'

>. The mo#ement o* air cause (ind to blo( *rom

the land to the sea'


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E0er+"se 4.6

SE'TI=N A : '!oose &!e )es& a$ser

1. The change in the temperature of an

ob'ect does not depend on. the mass of the ob'ect

B. the type of substance the ob'ect ismade of

'* the shape of the ob:ect


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)2 32 J

$. 8alculate the amount of heat required to raise the temperature of 6.3 kg of copper from &(68

to 0668. !pecific heat capacity of copper >66 2 kg-1 8-1*.

%mount o* heat re+uired& , mc∆!

'5 - 4 - /20).1

5 J

&. 8alculate the amount of heat required to raise the temperature of $.( kg of water from &$68

to 3$68. !pecific heat capacity of water >$66 2 kg-1 8-1*.

%mount o* heat re+uired& , mc!

$'. - 4$ - /5$0)$1

.$.& J

>. (6g block of a aluminium at 1$668 is cooled until >(68. ind the amount of heat is

released. . !pecific heat capacity of aluminium 566 2 kg-1 8-1*.

%mount o* heat released& , mc!

'6. - 7 - /3$04.1 . 2$.J

(. 6.$ kg of water at 668 is mixed with 6.0 kg of water at &668. ssuming that no heat is lost,

find the final temperature of the mixture. !pecific heat capacity of water >$66 2 kg-1 8-1*

%mount o* heat released& , %mount o* heat re+uired& ,

mc∆! mc∆!

'$ - 4$ - / 60 !1 '2 - 4$ - /! 0 )1

! 4C

SE'TI=N ': S&ru+&ure# ques&"o$s

16


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1. "n figure below, block of mass (kg at temperature 16668 is in contact with another block B

of mass $.$(kg at temperature $668.

ssume that there is no energy loss to the surroundings.

!a* ind the final temperature of and B if they are in thermal equilibrium. Ii#en the

specific heat capacity of and B are 566 2kg-1 8-1 and >66 2kg-1 8-1 respecti#ely.

-mount of heat released;by - 6 -mount of heat absorbed;by B

mc < (-) 6 mc < (B)

*&x %&& x ( 7& ?*? &'

!b* ind the energy gi#en by during the process.

Energy given by - 6 mc < (-)

6 x %&& x (7&& @ >?*?)

6 % %> 8

!c* uggest one method to reduce the energy loss to the surroundings.

..

11

B

16668 $668

(kg

$.$(kg

+ut them in a sealed polystyrene box*


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>.& UNDERSTANDING S(E'I>I' LATENT HEAT


• tate that transfer of heat during a change of phase does not cause a change in temperature

•


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!b* Bo"l"$%eCaora&"o$

-+ Sol"#"/"+a&"o$

-# 'o$#e$sa&"o$

1&

Tem erature

Time

.

Tem erature

Time

.

Tem erature

Time

.

Tem erature

Time

.

8olid li+uid

P ,melting

9solidli+uid;

3' From P to , the temperature does notchange e#en though heat is still being

absorbed'

$' The temperature is the melting point o* the substance'

)' The heat absorbed is used *or brea the li+uid begins to boil andall the li+uid has boiled at point 8'

?i+uid gas

> 8boiling

9li+uid gas;

3' From > to 8 the temperature does not

change e#en though heat is still beingreleased'

$' The temperature as same as the melting

point o* the substance and call as *ree@ing point'

)' The heat released is used *or rearranging the

molecules to *orm a solid'4' %t the point > the li+uid begins to *ree@e and

all the li+uid has been solid at point 8'

?i+uid solid

> 8

solidi*ication

9li+uidsolid;

3' From > to 8 the temperature does notchange e#en though heat is still being

released'

$' The temperature as same as the boiling poin

o* the substance)' The heat released is used *or rearranging th

molecules to *orm a li+uid'

>. %t the point > the gas begins to condense anall the gas has been li+uid at point 8'

gas li+uid > 8

condensation

9li+uid gas;


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>. is the heat absorbed by a melting solid. The specific latent

heat of fusion is the quantity of the heat needed to change 1kg of sol"# &o a l"qu"# at its

melting point without any increase in .. The ." unit of the specific

latent heat of fusion is 2kg-1.

(. ... is heat of #aporisation is heat absorbed during boiling.

The specific latent heat of #aporisation is the quantity of heat needed to change 1kg of l"qu"#

"$&o %as or #apour of its boiling point without any change in .. The ."

unit is 2kg-1.

1>

5atent heat of fusion

5atent heat of vaporisation

temperature

temperature

water ice

La&e$& !ea& a)sor)e#

- mel&"$%

!ea& los&

- sol"#"/"+a&"o$/reez"$%

water gas

La&e$& !ea& a)sor)e#

- )o"l"$%

!ea& los&

- +o$#e$sa&"o$


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0. Explain the application of pecific )atent 4eat abo#e+

+

-# 'ool"$% o/ )eCera%e

-e (reserCa&"o$ o/ >oo#

1(

Ahen ice melts; its large latent heat is absorbed from surroundings* 1his property

makes ice a suitable substance for use as a coolant to maintain other substance at a

low temperature* Beverage can be cooled by adding in several cubes of ice* Ahen the

ice melts a large amount of heat (latent heat) is absorbed and this lowers the

temperature of the drink*

1he freshness of foodstuff such as fish and meat can be maintain by placing

them in contact with ice* Aith its large latent heat; ice is able to absorb a large

quantity of heat from the foodstuff as its melts* 1hus food can be kept at a low

temperature for an extended period of time*


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-/ S&eam"$% >oo#

-% "ll"$% o/ Germs a$# Ba+&er"a

EER'ISE 4.7

Se+&"o$ A+

1. The graph in figure below shows how

the temperature of some wax changes asit cools from liquid to solid. %hich

section of the graph would the wax be a

mixture of solid and liquid9

10

!ood is cooked faster if steamed* Ahen food is steamed; the condensed water

vapour releases a quantity of latent heat and heat capacity* 1his heat flows to the

food* 1his is more efficient than boiling the food*

team that releases a large quantity of heat is used in the autoclave to kill germs

and bacteria on surgery equipment in hospitals*


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. :;

B* ,C

8. J


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. determining the rate of melting of ice

B. ensuring that the ice does not melttoo fast.

8. determining the a#erage #alue of the

specific latent heat of fusion of ice.

* determining the mass of ice that

melts as a result of heat from the

surroundings

0. calding of the skin by boiling water is

less serious then by steam. This is because

. the boiling point of water is less than

the temperature of steamB. the heat of boiling water is quickly

lost to the surroundings

'* steam has a high specific latent

heat*


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/')1/4$1/604 1 -/4$1/506 1 9Note : , absorbed by ) g o* (ater

- '7 .> UNDERSTANDING THE GAS LA

By the end of this subtopicL you will be able to +

15


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• Explain gas pressure, temperature and #olume in terms of the beha#ior of gas molecules.

•


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1. BoyleDs law states that *or a *i-ed mass o* gas& the pressure o* the gas is in#ersely

proportional to its #olume (hen the temperature is


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1. 8harlesD law states that *or a *i-ed mass o* gas& the #olume o* the gas is directly proportional

to its absolute temperature (hen its pressure is . 8omplete the diagram below.

4.4.7 (ressureJs La

$$

3'1967

( K T

That is ( constant T 4igher temperature

molecules mo#e

faster, greater

pressure

6

:7:a


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1. The pressure law states that for a fixed mass of gas; the pressure of the gas is directly

proportional to its absolute temperature when its volume is kept constant .

EERSI'E 4.4Gas La

1. mixture of air and petrol #apour is in'ected into the cylinder of a car engine when the

cylinder #olume is 166 cm&. "ts pressure is then 1.6 atm. The #al#e closes and the mixture is

compressed to $6 cm&. ind the pressure now.

P 3B 3 P $B $

/3'1/31 P $/$1

P $ .' atm

$. The #olume of an air bubble at the base of a sea of (6 m in deep is $66 cm&. "f the

atmospheric pressure is 16 m of water, find the #olume of the air bubble when it reaches the

surface of the sea.

P 3B 3 P $B $

/. 31/$1 /31B $

B $ 3$ cm)

&. The #olume of an air bubble is ( mm& when it is at a depth of h m below the water surface.

Ii#en that its #olume is 1( mm& when it is at a depth of $ m, find the #alue of h.

!tmospheric pressure 16 m of water*

P 3B 3 P $B $

/h 31/.1 /$ 31/3.1

.h . 35

h $2 m

$&

Rela&"o$s!" )e&ee$ ressure

a$# &emera&ure


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>. n air bubble has a #olume of M cm& when it is released at a depth of >(m from the water

surface. ind its #olume !M* when it reaches the water surface. !tmospheric pressure 16

m of water*

P 3B 3 P $B $

/4. 31/B1 /31/B $ 1

B $ .'. B cm)

(. gas of #olume $6m& at &68 is heated until its temperature becomes 368 at constant

pressure. %hat is the increase in #olume9

B 3 B $ & $ B $ '

T 3 T $ )6 $6) 56 $6)

B $ $)'$) m)

0. The air pressure in a container at &&68 is 1.> K 1H( / m-$. The container is heated until the

temperature is ((68. %hat is the final air pressure if the #olume of the container is fixed9

P3 P $ & 3'4 - 3. P $ '

T 3 T $ )) $6) .. $6)

P $ 3'. - 3. N m0$

. The #olume of a gas is 1 cm& at 1(68. The gas is heated at fixed pressure until the #olume

becomes triple the initial #olume. 8alculate the final temperature of the gas.

B 3 B $ & 3 ) '

T 3 T $ 3. $6) T $

T $ 524

T $ θ $ $6)

$>


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θ $ T $ D $6)

524 0 $6)

θ $ .73C

3. n enclosed container contains a fixed mass of gas at $(68 and at the atmospheric pressure.

The container is heated and temperature of the gas increases to 5368. ind the new pressure

of the gas if the #olume of the container is constant.!tmospheric pressure 1.6 K 16( /

rn$*

P3 P $ & 3' - 3. P $ '

T 3 T $ $. $6) 75 $6)

P $ 3'$4 - 3. N m$

5. The pressure of a gas decreases from 1.$ x 16( :a to 5 x 16( :a at >668. "f the #olume of the

gas is constant, find the initial temperature of the gas.

P3 P $ & 3'$ - 3. 7 - 3. '

T 3 T $ θ 3 $6) 4 $6)

θ 3 0$)3') C

43'6

(ART A: 'HA(TER 4

1. (kg iron sphere of temperature (668 is

put in contact with a 1kg copper sphereof temperature $& and they are put

inside an insulated box. %hich of the

following statements is correct when

they reach thermal equilibrium9


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E. The copper sphere will ha#e a

temperature of (668.

. Both the sphere ha#e the sametemperature.

I. The temperature of the iron

sphere will be lower than (66

8

$. "n the process to transfer heat from one

ob'ect to another ob'ect, which of thefollowing processes does not in#ol#e a

transfer to material9

. 8on#ection

B. Maporisation8. Jadiation


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beha#iour of gas molecules in a

container9

. Ias molecules mo#e randomlyB. Ias molecules collide elastically

with the walls of the container

8. Ias molecules mo#e faster astemperature increases


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Table 1

!a* !i* tate the principle used in a liquid- in ?glass thermometer.!1m*

........................................................................................................................................

!ii* Briefly explain the principle stated in !a*!i* !&m*

.

.

.

!b* Table 1 shows the characteristic of > types of thermometer+ ,B 8 and


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..

!c* The length of the mercury column in uncalibrated thermometer is 0.6cm and 13.( cm at

668 and 16668. respecti#ely. %hen the thermometer is placed in a liquid, the length of

the mercury column is 1>.6cm

!i* 8alculate the temperature of the liquid

T!e &emera&ure o/ &!e l"qu"#


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!b* the rate of heat supplied to the water

Ra&e o/ !ea& sul"e# &o &!e a&er 16 ;

16s

18 s91

!c* the specific heat capacity of the metal block :

Hea& sul"e# )2 me&al )lo+F ( !ea& %a"$e# )2 a&er

.8 0 + 0-1 946 16 ;

+ 474 F%91 '91

&. student performs an experiment to in#estigate the energy change in a system. 4e prepares a

cardboard tube (6.6 cm long closed by a stopper at one end. )ead shot of mass (66 g is

placed in the tube and the other end of the tube is also closed by a stopper. The height of the

lead shot in the tube is (.6 cm as shown in igure &.1. The student then holds both ends of

the tube and in#erts it 166 times !igure &.$*.

!a* tate the energy change each time the tube is in#erted.

..

..

!b* %hat is the a#erage distance taken by the lead shot each time the tube is in#erted9

=*& cm

&6

igure &.1 igure &.$

Dravitational potential energy kinetic energy heat energy


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igure !a* igure !b*



!c* 8alculate the time taken by the lead shot to fall from the top to the bottom of the tube.

S u& a&6

.48 -1&6

& .7s

!d* fter in#erting the tube 166 times, the temperature of the lead shot is found to ha#e

increased by &68.

i. 8alculate the work done on the lead shot.

orF #o$e -1 m%!

1 0 .8 0 1 0 .48

668

ii. 8alculate the specific heat capacity of lead.

m+ 3 668

+ 668

-.8 0 7

18 F%91 '91

iii. tate the assumption used in your calculation in !d*ii.

...

.

(ART ': E(ERIMENT

1. Before tra#elling on a long 'ourney, )uqman measured the air pressure the tyre of his car as

shown in igure !a* 4e found that the air pressure of the tyre was $66 k:a. fter the 'ourney,

)uqman measured again the air pressure of the tyre as shown in igure !b* 4e found that the

air pressure had increase to $>( k:a. )uqman also found that the tyre was hotter after the

'ourney although the si=e of the tyre did not change.

@sing the information pro#ided by )uqman and his obser#ations on air pressure in the

tyre of his car+

&1

No heat loss to the surroundingsF-ll the gravitational potential energy is converted

into heat energy


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8hoose suitable apparatus

such as pressure gauge, a

round-bottomed flask and any other apparatus that may he necessary. "n your description,

state clearly the following+

i. im of the experiment,

ii. Mariables in the experiment,

iii. )ist of apparatus and materials,

i#. rrangement of the apparatus,

#. The procedure of the experiment including the method of controlling the

manipulated #ariable and the method of measuring the responding #ariable,

#i. The way you would tabulate the data,

#ii. The way you would analyse the data. O16 marksP

&$

!a* tate one suitable inference that can be

made. O1 markP

!b* tate appropriate hypothesis for an

in#estigation. O1 markP

!c*


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"nference -t constant volume; the air pressure depends on the temperature

4ypothesis -t constant volume; the air pressure increase as the temperature

increases

im 1o investigate the relationship between the air pressure and the

temperature at constant volume*

Mariable 8onstant #ariable + -ir temperature

Canipulate #ariable + -ir pressure

Jesponding #ariable + Golume of air

Caterial and pparatus Rou$#9)o&&om /lasF, ru))er &u)e, Bour#o$ %au%e, )eaFer, s&"rrer,

&!ermome&er, "re %auze, &r"o# s&a$# a$# Bu$se$ )ur$er.rrangement of

apparatus

:rocedure • 1he apparatus is set up as shown in the diagram above*

• 1he beaker is filled with ice#cold water until the flask is

completely immersed*

• 1he water is stirred and the initial temperature reading

taken* 1he pressure reading from the bourdon gauge is also

taken*

• 1he water is heated and constant stirred* Ahen the water

temperature increases by 7&&'; the Bunsen burner is

removed and the stirring of water is continued* 1he

temperature and pressure readings of the trapped air are

recorded in the table

• 1he above procedure is repeated until the water temperature

&&


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almost reaches boiling point*

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chapter-4-heat (answer).pdf

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