F2 Science Chapter 6 Air Pressure

7/28/2019 F2 Science Chapter 6 Air Pressure

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Kinetic theory of gases states that particles in amatter are always MOVING or VIBRATING.

Gas particles in a container COLLIDE with each

other and with the walls of the container all the time. Air or gases are matter that have particles that move

randomly in ALL direction.


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- Gas particles in a container are always COLLIDINGwith the walls of the container. These collision resultin a GAS PRESSURE.

- Gas pressure in a closed container increases whenthe particles in the container move FASTER andcollide more FREQUENTLY with the walls ofcontainer.


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The Earth is surrounded by a thick layer of air calledATMOSPHERE.

The air in the atmosphere has mass .

Air in the atmosphere has particles that arecontinually moving and colliding with things onEarth. These collisions produce AIR PRESSURE.

Air presses down on all things in the Earth's surface.

The pressure exerted by air is known as air

pressure or atmospheric pressure.


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The features of air pressure are :(a) acts in all direction(b) changes from one place to another(c) decreases the higher you go above

ground level.This feature exists :-

(because at high place, theamount on

air decreases. This explains why the

air pressure on the top of a mountain

is lowerthat at the foot of the

mountain.)


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Change with temperature. The HIGHER thetemperature, the HIGHER the air pressure.

Change with volume. The LOWER the volume, the

HIGHER the temperature.Summary

Aspects Low High

Height of a place High air pressure Low air pressure

Temperature Low air pressure High air pressure

Volume High air pressure Low air pressure


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Proof to show the existence of air pressure


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C) A straw is partly submerged into a beaker and itstop is covered with a finger. Then the straw is

withdrawn from the water.

Observation :

1.A column of water remains in the straw.2. This shows that there is a force supporting thecolumn of water. When the finger is removed, thecolumn of water flows out.


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d) i) A soft can drink is filled with a small amount of

water.

ii) The can is heated until the water in it boil

vigorously.iii) Then the can is removed from flame and

immediately inverted and lowered into water.


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The soft drink can collapse or crushes inwards. This is because there is large force acting on the can

from all directions.


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Factors that influence air pressure

1. Air is a mixture of gases made up of particles that

move randomly in all directions.

2. Air pressure increases when air is heated. This is

because the air particles obtain more energyandcollide with the walls of the container morevigorously.

3. When air compressed, air particles collide with the wallsof the container more frequentlyand this makes the air

pressure increase.

4. The increasing volume of gas ( adding of gases) in thecontainer increases air pressure.


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1) Syringe

The piston is pulled upwards to increase the volumeof air in the barrel.

The increase in the volume of the barrel will causethe air pressure in the barrel decrease.

The higher air pressure outside the syringe forcesthe liquid through the nozzle into the barrel.


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2) Spraying pump


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3) Siphon


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4) Drinking straw


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5) Filter pump


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6) Sucker Hook


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7) Dropper


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1) Clearing a blocked pipe


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2) Pouring condensed milk

It is hard to pour out a can of condensed milk if onehole is made.


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This is because the milk that flows out of the canreduces the pressure inside the can.

The higher air pressure outside prevents the milk

from coming out. This problem can be solved if another hole is made

on the opposite side of first hole.

This second hole enables air to enter and push the

milk out from the first hole.


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When a gas is placed under high pressure, is changes

and becomes a liquid.

The liquid will become a gas again when the

pressure is released. Example of gases under high pressure.

a) Oxygen gas tank is used in hospitals, diving and etc.


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Hydrogen gas is used for welding and as rocket fuel.

a) Welding machine b) rocket


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c) Liquefied Petroleum Gas ( LPG) is used as fuel athome and vehicles.

d) Carbon dioxide is used in fire extinguishers.

(c) (d)


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(e)


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F2 Science Chapter 6 Air Pressure

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