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CW May 13, 2019 7. What is Boyle’s Law? What is volume? What is temperature? What is pressure?
CW May 13, 20197. What is Boyle’s Law?
What is volume?
What is temperature?
What is pressure?
CW
What is volume? The space taken up by a 3d object.
What is temperature? The average energy per particle of a substance
What is pressure?. The concentration of force.
May 13, 20197. What is Boyle’s Law?
Learning objectives
Use the relationship between the pressure and volume of a fixed mass of gas has at constant temperature: p1V1 = p2V2
How does volume affect pressure?
We will reduce the volume of air and measure the pressure
What will happen qualitatively?
Draw a line of best fit
Explain the mathematical relationship between p and V
Plot the data
A graph to show the relationship between volume and pressure (fixed mass, constant temperature)
Pres
sure
/ kP
a
0
50
100
150
200
250
300
Volume / ml
0 10 20 30 40 50 60
Volume / ml Pressure / kPa
60
55
50
45
40
35
30
25
20
Explain why this is the case.
What mathematical relationship exists between p and V?
Write a conclusion to the experiment.
A graph to show the relationship between volume and pressure (fixed mass, constant temperature)Pr
essu
re /
kPa
0
50
100
150
200
250
300
Volume / ml0 10 20 30 40 50 60
Volume / ml Pressure / kPa
60 101.3
55 112.0
50 120.7
45 136.3
40 150.3
35 173.1
30 198.6
25 236.5
20 292.3
A graph to show the relationship between volume and pressure (fixed mass, constant temperature)Pr
essu
re /
kPa
0
50
100
150
200
250
300
Volume / ml0 10 20 30 40 50 60
Volume / ml Pressure / kPa
60 101.3
55 112.0
50 120.7
45 136.3
40 150.3
35 173.1
30 198.6
25 236.5
20 292.3
p ∝ 1V
p = k × 1V
As the volume increases, pressure decreases
Explain why this is the case.
What mathematical relationship exists between p and V?
Write a conclusion to the experiment.
A graph to show the relationship between 1/V and p (at constant mass and temperature)
Pres
sure
/ kP
a
0
50
100
150
200
250
300
1/(volume/ml)0 0.01 0.02 0.03 0.04 0.05
Volume / ml 1/(Volume/ml) Pressure / kPa
60
55
50
45
40
35
30
25
20
Draw a line of best fit
Explain the mathematical relationship between p and V
Plot the data
A graph to show the relationship between 1/V and p (at constant mass and temperature)Pr
essu
re /
kPa
0
50
100
150
200
250
300
1/(volume/ml)
0 0.01 0.02 0.03 0.04 0.05
Volume / ml 1/(Volume/cm3) Pressure / kPa
60 0.017 101.3
55 0.018 112.0
50 0.020 120.7
45 0.022 136.3
40 0.025 150.3
35 0.029 173.1
30 0.033 198.6
25 0.040 236.5
20 0.050 292.3
Explain why this is the case.
What mathematical relationship exists between p and V?
Write a conclusion to the experiment.
A graph to show the relationship between 1/V and p (at constant mass and temperature)Pr
essu
re /
kPa
0
50
100
150
200
250
300
1/(volume/ml)
0 0.01 0.02 0.03 0.04 0.05
Volume / ml 1/(Volume/cm3) Pressure / kPa
60 0.017 101.3
55 0.018 112.0
50 0.020 120.7
45 0.022 136.3
40 0.025 150.3
35 0.029 173.1
30 0.033 198.6
25 0.040 236.5
20 0.050 292.3
p = k × 1V
pV = k
Explain why this is the case.
What mathematical relationship exists between p and V?
Write a conclusion to the experiment.
p1V1 = p 2V2
pressure at the start,
in Pa, atm, N/m2
volume at the start,
in m3, l
pressure at the end,
in Pa, atm, N/m2
volume at the end, in m3, l
Rearrange to find four versions of this formula.
Explain why this formula is correct.
Write down the formula.
5. Solids, liquids and gases 8. What is Boyle’s Law?
Steps Worked example Practice 1 Practice 2
Read the question carefully. Atmospheric pressure is 100 kPa. Some air is sealed in a container with volume 2 m3. What would be the pressure of the air if you reduced its volume to 0.2 m3?
Atmospheric pressure is 100 kPa. Some air is sealed in a container with volume 1.5 m3. What would be the pressure of the air if you reduced its volume to 0.5 m3?
Atmospheric pressure is 100 kPa. Some air is sealed in a container with volume 2 m3. What would be the volume of the air be if you increased its pressure to 300 kPa m3?
Write what you know: highlight/record the information from the questions including what you want to find out.
p1 = 100 kPa, V1 = 2 m3, V2 = 0.2 m3, p2 = ?
Convert any data to appropriate values (for example g to kg, or cm to m)
Not required
Write down the equation that links the variables together
p1V1 = p2V2
Rearrange the equation to make the unknown the subject
p2 = (p1V1 ) / V2
Substitute your data into the equation, including the units
p2 = (100 kPa x 2 m3 ) / 0.2 m3
Calculate the answer, leaving a unit and an appropriate number of sig figs (same as data). Check that the answer makes sense and underline.
p2 = 1000 kPa
Pressure increases as volume decreases so makes sense.
Learning objectives
Use the relationship between the pressure and volume of a fixed mass of gas has at constant temperature: p1V1 = p2V2
Questions Q1.
(a) A diver breathes air from a cylinder when he is under water.
(i) The cylinder contains 8 litres of air at 200 times atmospheric pressure. The air is released from the cylinder at normal atmospheric pressure. The diver needs 16 litres of air per minute. Calculate the maximum amount of time that the diver can breathe under water using this cylinder.
(3)
time = ........................................................... minutes (ii) When the diver breathes out, bubbles are released. Suggest why the bubbles expand as they rise to the surface.
(2) .............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(b) A student wants to investigate how the volume of a balloon changes with pressure.
Questions Q1.
(a) A diver breathes air from a cylinder when he is under water.
(i) The cylinder contains 8 litres of air at 200 times atmospheric pressure. The air is released from the cylinder at normal atmospheric pressure. The diver needs 16 litres of air per minute. Calculate the maximum amount of time that the diver can breathe under water using this cylinder.
(3)
time = ........................................................... minutes (ii) When the diver breathes out, bubbles are released. Suggest why the bubbles expand as they rise to the surface.
(2) .............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(b) A student wants to investigate how the volume of a balloon changes with pressure.
8 x 200 = V x 1 1600/1 = V
1600/16 = 100 mins
Pressure decreases as depth decreases
p = h⍴g
If temp constant, pV is constant
Use displacement method
Submerge in water and
Measure volume of displaced water
Not a fair test
There will be a change in temperature/volume
7. What is Boyle’s Law?
Write down your best answer to this question.
Include any key words or diagrams you think are
necessary.
