Physics Presentation

4.4 -UNDERSTANDING THE GAS LAW

Ø 4.4.1 Boyle’s LawØ 4.4.2 Charles’ LawØ 4.4.3 Pressure’s law

4.4 Understanding the Gas Laws

● The volume of the gas is equal to the volume of the container.

● The molecules move freely in random motion an fill up the whole space in the container.

VOLUME

● The volume of the gas is equal to the volume of the container.

VOLUME● The molecules move freely in random motion an fill up

the whole space in the container.

TEMPERATURE● The molecules are in continuous random motion and have an average kinetic

energy which is proportional to the temperature

● The molecules are in continuous random motion and have an average kinetic energy which is proportional to the temperature

TEMPERATURE

PRESSURE● When a molecule collides with the wall of the container and bounces back, there is a change

in momentum and a force is exerted on the wall.● The force per unit area is the pressure of the gas.● The molecules are in continuous random motion

PRESSURE● The force per unit area is the pressure of the gas.● When a molecule collides with the wall of the container and bounces back, there is a change

in momentum and a force is exerted on the wall.● The molecules are in continuous random motion

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4.4.1 Boyle’s Law

Boyle’s Law states that for a fixed mass of gas, the pressure of the gas is inversely proportional to its volume when the temperature is kept constant.

That is PV = constant or =

When the volume of a gas is reduced, the pressure of the gas increases.

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4.4.1 Boyle’s Law

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The graphs of a gas obeying Boyle’s Law

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APPLICATION OF BOYLE’S LAW

The oxygen cooled under high pressure so that the volume of the oxygen can be reduced.

Due to the high pressure in the tank, the tank is made of metals which are hard and thick.

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Extrapolating Graph

Relationship between Celcius and Kelvin.

oC = ( + 273) Ө ӨK

The temperature of -273oC is the minimum temperature which can be achieved by the gas.

This temperature is known as absolute zero.

Absolute Zero of Temperature

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4.4.2 Charles’ Law

Charles’ law states that for a fixed mass of gass, the volume of the gas is directly proportional to its absolute temperature when its pressure is kept constant.

That is = constant or

The volume of a gas, at constant pressure, increases with temperature. Click

This

APPLICATION OF CHARLES’ LAW

When the air in a hot-air gas balloon is heated at atmospheric pressure, its temperatures.

According to Charles’ law, the volume of a gas increases when its temperature is increased at constant volume.

The balloon rises when buoyant force on the balloon is greater than the weight of the balloon.

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4.4.3 Pressure Law

The pressures law states that for a fixed mass of gass, the pressure of the gas is directly proportional to its absolute temperature when its volume is kept constant.

That is = constant or

The pressure of a gas increases with its temperature.

APPLICATION OF PRESSURE LAW

When the car is moving, the tyres will roll on the surfaces of the road & causes compression on the tyres.

This will increases the temperature in the tyres & therefore increases the air pressure in the tyres.

When the air pressure in the tyres becomes higher, it might explode

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Boyle’s Law

=

Pressure Law

Charles’ Law

The Gas Laws & Important Formulae

P

V T

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SUMMARY

What Have We Learned :

ü Understanding Heat as a Form of Energyü Using the Laws

THE END