Conor

Mullen – N5 Physics Assignment

Boyle’s Law

Aim

To investigate the effect on pressure when the volume of a

fixed mass of gas is decreased.

Underlying Physics

In a gas, intermolecular forces are weak which allows

particles to move around. As they move around, they may collide with each other

or the walls of their container. If the volume of the container is decreased,

the number of particles per unit area is increased. Hence, collisions occur

more frequently. If the temperature is increased, the particles move with more

kinetic energy which means collisions occur more often and due to collection

more kinetic energy, the particles collide with a greater force.

Pressure can be calculated using the equation:

Where P is the pressure in Pascals (Pa)

Where F is the force in Newtons (N)

Where A is the area in meters squared (m2)

Therefore, it can be determined that if area is decreased,

pressure will increase and if Force is increased, pressure will increase.

Lord Kelvin created a new temperature scale. At -273oC

particles have no kinetic energy and so do not move or strike against the walls

of the container. Hence, to convert from degrees Celsius to degrees Kelvin,

simply subtract 273. It is for this reason that when measuring the temperature

of a gas, it would make sense to use the Kelvin scale.

The Gay-Lussac Law states that a gas which is at a constant

volume has a pressure which is directly proportional to the Kelvin scale. This

law is responsible for the equation:

Where P is pressure in Pascals (Pa)

Where T is temperature (Degrees Kelvin)

Where C is a constant

This means that as pressure increase, so does the temperature.

Method

A fixed mass of gas was trapped in a tube with oil. Going

along the tube was scales indicating the volume of air inside. The volume of

air was altered by pumping oil into the tube. The tube was connected to a

bourdon-gauge. We measured the volume of air inside the tube and then the

pressure in kPa.

Air Volume (cm3)

1/Volume

(cm-3)

Pressure

1 (kPa)

Pressure 2

(kPa)

Pressure 3

(kPa)

Average

Pressure (kPa)

10

0.1

256

253

259

256

15

0.07

180

180

180

180

20

0.05

148

130

130

136

25

0.04

109

100

91

100

30

0.03

80

83

77

80

Complimentary Evidence

Taken from: https://www.google.co.uk/search?q=pressure+vs+1/volume=strict=lnms=isch=X=0ahUKEwj5vKmfk9zYAhUBB8AKHUK4A28Q_AUICigB=1366=637#imgrc=PSUZhub0YmmhPM: on

16/01/2018

Analysis

This graph shows that as volume increases, pressure decreases.

The line graph is a straight line which goes through the origin, hence

indicating that pressure and volume are inversely proportional.

My graph also shows that pressure and volume are inversely

proportional because my graph adopts the same straight line through the origin

when plotting Pressure against 1/Volume.

Conclusion

Therefore, I am able to conclude that pressure and volume are

inversely proportional. Subsequently, if the volume of a gas is decreased, the

pressure will increase.

Evaluation

To increase the accuracy of my results, I repeated the

experiment three times and then calculated the average. This means that any

inaccurate results were more likely to be cancelled out by more accurate

results.