modul 11 -air pressure

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PROGRAM DIDIK CEMERLANG AKADEMIK (PDCA) 2009PMR

MODULE 11SCIENCE

PROGRAM DIDIK CEMERLANG AKADEMIK

PMR 2009

MODULE 11

JABATAN PELAJARAN NEGERI PULAU PINANG (JPN PP)

BAHAGIAN PENYELARASAN PENYERTAAN BUMIPUTERA (BPPB),UNIT PENYELARASAN PELAKSANAAN,

JABATAN PERDANA MENTERI

LEMBAGA KEMAJUAN WILAYAH PULAU PINANG ( PERDA ),UNIT PENYELARASAN PELAKSANAAN,

JABATAN PERDANA MENTERI

PUSAT URUS ZAKAT PULAU PINANG (PUZ),MAJLIS AGAMA ISLAM NEGERI PULAU PINANG

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MODULE 11SCIENCE

AIR PRESSURE

CONTENTS: A. Understanding air pressureB. Applying the principle of air pressure in daily life

CHAPTER HIGHLIGHTS (30 minutes)

A. Understanding air pressure

a) Kinetic theory of gases explains the following:

Air consist of particles which move freely in all directions.The particles collide with each other and exert a force.These forces produce a pressure on the surface.

b) The air in the atmosphere presses on the surface of all objects. This isknown as air pressure.

c) Atmospheric pressure is measured by means of an aneroid barometerin cm of mercury on N/m2 . Example pressure at sea level is about 76cm of mercury or100 000 N/m2 .

d) The presence of air pressure can be shown by the following activitiesSucking air out from a plastic bottle

When air is sucked out of the plastic bottle, the bottle collapses inwards due to airpressure outside the bottle pressing inwards. The air pressure in the bottle isreduced.

(ii) A glass of water and a piece

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Air

To suction pump

pressure

High air

To suction pump

Plastic bottleLow air

pressure

Beginning End

Air pressure

Beginning End

cardboard

water


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When the hand supporting the cardboard is withdraw, the cardboard does not fallin spite of the weight of the water in the glass pushing down on it. This is due to theair pressure pressing upwards on the cardboard.

(iii) Rubber cups

Press two rubber cups together so that the air enclosed by the cups is forced out. Itis difficult to separate the cups now. This is because atmospheric pressure ispressing on the cups.

e) Factors affecting air pressureAir pressure increases when i. volume is decreased

ii. Temperature is increased.

B. Applying the principle of air pressure in daily life

( i )

( ii )

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Rubber cuphandle


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MODULE 11SCIENCE

(iii)

(v)

( g ) Gases can be changed into liquids by compressing them under highpressure in gas cylinders and aerosol cans.

( h ) The following safety measures should be followed when using gasunder high pressure:-

Do not place the tank near a heat source.

Always place the tank upright .

Do not dispose can aerosol can in a fire.

Activity (60 minutes)

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(iv)


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1. What are the apparatus used for ? Match the apparatus with the explanationbelow.

( a ) Air expand when heated.

( b ) Air diffuses through the walls of the balloon

( c ) Air has weight

( d ) Air occupies space

( e ) Air exerts a pressure.

( f ) One fifth of air is used for burning

2. Rearrange the steps to explain what happen in the figures below.Write the numbers 1 10 in the boxes.

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A The pressure in the can decreases

B Close the cap tightly

C The can becomes dented

D Heat the water until its boils

E The air pressure in tin increases

F There are more liquid particles in the can now

G More liquid particles become gas particles

H Rinse the hot can with cold water

I The air pressure outside the can is higher

J The gas condenses and forms a liquid

3. Fill in the blanks.

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(a) The ____________ states that a gas consists of tiny , discrete particles.

(b) These gas particles are constantly ______________.

(c) They move in a ____________ manner.

(d) The gas particle __________ with one another.

(e) Gas particle also collide with the __________ of the container.

(f) These collision result in __________ .

(g) The layer of air that _________ the earth exerts a pressure on all objectson the surface of the earth.

(h) The _____ a place is above sea level, the less air pressure there is .

(I) When air is _________ , the air pressure increases.

(j) When the volume of air _________ , the air pressure decreases.

4. Fill in the blanks to learn more about air pressure.

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random surrounds air pressure Kinetic Theory of Gases moving

increases collide higher heated walls


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Air pressure in an ( 1 )______________ container depends on two factors.

These are ( 2 ) __________ of the container and ( 3 )___________ of the air.

Air pressure is caused by air particles ( 4 )___________ and with the walls of

( 5 )___________.We can changed the ( 6 )____________ of the container

shown in the n figure on the previous page by ( 7 ) __________the piston up

and down. When the ( 8 )______ is pushed down , the volume of the container

becomes( 9 )_________ .The ( 10 ) __________ between the particles and also

with the (11 ) _________increases . .These causes the air pressure inside the

container to increase. When the piston is pushed up , the volume of the

container( 12 )_________ .The collision rate ( 13 )__________ and so too does

the ( 14 )_________ in the container. When the air in the container is heated the

air particles ( 15 ) _______.Therefore , the air particles move ( 16 )__________.

The ( 17 ) ___________ of collision between air particles and the walls of the

container increases . When the air is cooled it has ( 18 ) __________ kinetic

energy. The collision rate decreases ( 19 )__________ the air pressure ( 20 )

____________ the container decreases.

ASSESSMENT (60 minutes)

SECTION A

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1. Which activity below applies the principle of air pressure?

A. Using instant milk powder to make a drink of milk.B. Obtaining pure water from sea water.

C. Removing water from an aquarium using a siphon.D. Using baking powder to bake a fluffy sponge cake.

2. Which of the following is not included in the kinetic theory of gases?

A. Gas particles are always moving in a straight path.B. Gases are made up of discrete particles.C. Gas particles have kinetic energy.D. Gas particles exert pressure.

3. In which situation will the air pressure increase?

A. Use a bigger container to store the gas.B. Store the gas in a cylinder.C. Go up a mountain.D. Increase the temperature of the gas.

4. The Figure 1 shows a hook stuck onto a wall to hang a load

Figure 1

What modification could be made to ensure the rubber sucker sticks more stronglyon the wall to support more load?

A. Use a bigger hookB. Use a smaller hookC. Enlarge the rubber sucker diameterD. Reduce the rubber sucker diameter

5. Figure 2 shows a boy using a straw to drink.

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Wall

Rubber sucker

Hook


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Figure 2

Which of the following observation and explanations are true about the air pressureat X, Y and Z?

Observation Explanation

Pressure at X, Y and Z compared to theatmospheric pressure

X Y Z

A Water can be suckedup

Different Same Different

B Water can be suckedup

Same Same Same

C Water cannot besucked up

Same Different Same

D Water cannot besucked up

Different Different Same

6. The diagram 2 shows a spraying pump

What will happen when the piston is pushed forward?

A Air pressure at X is lower and air pressure in the container increases.B Air pressure at X is higher and air pressure in the container decreasesC Air pressure at X decreases and air pressure in the container remains the sameD There is no change in the air pressure at X and air.

7. Which of the following instruments uses the principle of air pressure?

I A fountain penII A vacuum cleanerIII A syringeIV A stethoscope

A I and III only C I,II and III onlyB II and IV only D I,II,III and IV

8 Why is the gas stored under high pressure in a cylinder?

A It is easy to compress the gasB It is easy to store compress gases

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C Only cylinders can be used to store gasD Cylinder makes the gas lighter

9 Why does water boils at a temperature lower than 100C at the top of a mountain?I The surrounding temperature is coldII The air pressure is less

III Water molecules escape from the liquid easily

A II onlyB III onlyC II and III onlyD I,II and III

10 The layer of air above the earth exerts a pressure on all objects on the surface ofthe earth. Why dont we feel this pressure?

I Our bodies are specially adapted to this pressure.II The blood in our arteries exerts a similar pressure

III Air pressure is only exerted on non-living things

A I onlyB I and II onlyC II and III onlyD I,II and III

11 A balloon filled with hydrogen increases in size as it rises into the air. This is due to.

A. the rubber balloon becoming weaker.B. the temperature of the hydrogen in the balloon increasingC. air pressure in the atmosphere gradually decreasing

D. air in the atmosphere diffusing into the balloon.

12 Which of the following involved use the application of air pressure?Clearing a blocked pipe using a plungerPouring out condensed milk from a canHanging objects on a tile wall using a rubber sucker.

A. I and II only B. I and III onlyC. II and III only D. I, Ii, III

13. Air pressure may be defined as

A. the force of air acting on one square unit.B. the weight of 1 m of airC. the mass of air acting on a surfaceD. the kinetic energy present in the air molecules.

14. A ping-pong ball placed in hot water returns to its original shape. This isbecause

A. The ball is made up of an elastic material.B. The air pressure in the ball is increased

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C. The hot water pulls the material of the ball outwardsD. The air particles in the ball have become bigger.

15. Gases stored under high pressure in cylinders include

I. cooking gas

II. carbon dioxideIII. ammonia

A. I, II and IIIB. I and II onlyC. II and III onlyD. I only

SECTION B

Figure 1

1. Figure 1 shows a hot air balloon .

( a ) ( i ) What can be said about pressure in the balloon and pressure in theAtmosphere ?

______________________________________________________[ 1 mark ]

( ii ) Explain how the hot air balloon rises up ?

_____________________________________________________

____________________________________________________ [ 2 marks ]

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Figure 2

( b ) ( i ) The cardboard does not fall when the glass of water is inverted.Why ?

____________________________________________________ [ 1 mark ]

( ii ) Does the air pressure act on the cardboard only or at all direction ?

___________________________________________________ [ 1 mark ]

( iii ) How would you describe air pressure ?

___________________________________________________

___________________________________________________[ 2 marks ]

Figure 3

2. The experiment shows that the effect of force on pressure. The brickstones used are identical.

( a ) ( i ) Which brick stone sinks deeper ?

_________________________________________________ [ 1 mark ]

( ii ) Explain why brick stone Y sinks deeper ?

_______________________________________________ [ 1 mark ]

( iii ) What inference can be made from your observation ?

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_______________________________________________ [ 1 mark ]

( b ) ( i ) Define pressure .

________________________________________________ [ 1 mark ]

3. (a) Name three devices which make use of air pressure.

i. ____________________________

iI. ____________________________

iii. ____________________________ [3 marks]

(b) In what state is the insecticide in aerosol?

___________________________________________________ [ 1 mark ]

(c ) Name another substance that can be purchased in an aerosol.

___________________________________________________ [ 1 mark ]

(d) State one precaution you should take when using an aerosol.

___________________________________________________ [ 1 mark ]

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modul 11 -air pressure

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