Boyle’s Law
Purpose
In this lab, a given quantity of gas (air) is trapped in a cylinder
(medical syringe) and subjected to changing pressure. Books
stacked on top of the syringe change the pressure on the trapped
gas. As the pressure or number of books changes, the responding
change in gas volume is recorded. Atmospheric pressure is
derived from the data. Data are used to graphically show the
inverse and proportional nature of Boyle’s law where PV  k .
Ptotal  Pbooks  Pair
Equipment
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
Boyle’s law kit
book- 6
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graph paper
ruler
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
pencil
colored pencil
Procedure
1. Remove the contents of the Boyle’s law syringe kit.
2. Remove the red cap from the tip of the syringe. (This may be difficult. Twist and pull the cap
at the same time.)
3. Pull back on the plunger to draw in the maximum readable volume of air. Replace the red
cap.
4. Assemble the remaining pieces of the apparatus.
5. Place one book on top of the wooden block attached to the plunger. Be careful to hold the
syringe firmly in place and do not exert any downward pressure on the book as it is balanced.
Record the volume to the nearest 0.1 cc (mL) in the Trial 1 column of Data Table 1.
6. Continue stacking and balancing the remaining textbooks until all six have been stacked.
Record the volume for each as you did in the step above.
7. Remove all books. Uncap the syringe. Re-establish the maximum volume of air in the syringe.
Recap the syringe. Repeat the stacking of the textbooks and recording of air volumes for Trials 2
and 3.
Calculations and Inverse Relationship
8. Determine the V avg. for each pressure in books. Round to the nearest 0.001 cc (mL). Record
the average volume values in the appropriate column of Data Table 2.
9. Determine the Uncertainty in V avg.. Round to keep three significant digits. To find the
Uncertainty in V avg., determine the absolute differences of each volume reading for each P
(books) from the V avg. for that number of books. Then average these absolute differences for
each P (books) and record as the experimental Uncertainty for that amount of pressure in
books.
10. Turn the graph paper to have a landscape orientation.
SC6. Students will understand the effects motion of atoms and molecules in chemical and physical processes.
a. Compare and contrast atomic/molecular motion in solids, liquids, gases, and plasmas.
 You exceeded the standard(s).
 You met the standard(s).
 You did not meet the standard(s).
Boyle’s Law
11. Draw the x-axis one-third of the way up from the bottom of the graph paper.
12. Label the x-axis as Volume (mL) and the y-axis as Pressure (books).
13. Plan scales for each axis that make use of most of the graph paper. Begin each scale at zero.
14. Plot the points. Draw a horizontal line through each point that extends to the left and right
an amount equal to the Uncertainty determined for each P (books). This allows for more
flexibility in constructing the curve.
15. Connect the data points using the best smooth curve. The curve should have a hyperbolic
shape to denote the inverse nature of the relationship between pressure and volume in Boyle’s
law.
Proportionality Test and Confirmation
16. Determine the reciprocal (1/V) of each V avg.. Use the x –1 or 1/x key on your calculator.
Round to keep three significant digits. Record these values in the appropriate column of Data
Table 2.
17. To determine the Uncertainty for each 1/V, determine the Lowest 1/V and Highest 1/V in
the following manner. For each P (books), add its Uncertainty in V avg. to its V avg. and determine
the reciprocal of the sum. Keep three significant digits. Record these reciprocal values in the
Lowest 1/V column of Data Table 2. Now, for each P (books), subtract its Uncertainty in Average
V from its Average V and determine the reciprocal of the difference. Keep two significant
digits. Record these reciprocal values in the Highest 1/V column of Data Table 2.
18. Using a different color pencil, plot P (books) versus Average 1/V on the same graph used to
show the inverse relationship. A new horizontal scale labeled
1/V (mL -1) must be constructed. Use the top of the graph for recording the new scale. Be sure
to allow for a (0,0) point on the graph. Draw a horizontal line through each point that extends
to the left and right an amount equal to the Lowest 1/V and Highest 1/V values determined for
each P (books).
19. Draw the best straight line making sure to cross the x and y-axes. The straight line should
cross at the (0,0) point; however, the unaccounted for added pressure of the atmosphere will
cause the y-intercept to be below the (0,0) point.
20. Extend the y-axis scale into Quadrant IV of your graph. Be sure to use the same scaling as
you extend the P (books) into the negative range of values.
21. Determine by how much pressure in books the straight line must be moved upward causing
the straight line to cross at the (0,0) point. This is equivalent to the pressure exerted on the
books by the atmosphere around them. Record this value in the Pressure Air column of Data
Table 2 for each P (books) value.
22. Determine the Total P by adding the Pressure Air (books) to the P (books) for each number
of books. Record these values in the Total P column of Data Table 2.
23. To verify the mathematical relationship in Boyle’s law ( PV  k ), multiply the Total P values
by the Average V values for each number of books. The products should remain fairly constant.
SC6. Students will understand the effects motion of atoms and molecules in chemical and physical processes.
a. Compare and contrast atomic/molecular motion in solids, liquids, gases, and plasmas.
 You exceeded the standard(s).
 You met the standard(s).
 You did not meet the standard(s).
Boyle’s Law
Name:
Date:
Write in pencil only.
Boyle’s Law Data Table 1
Pressure
(Books)
1
Trial 1
Trial 2
Volume of Gas (mL/cc)
Trial 3
Volume (avg)
P x V avg.
2
3
4
5
6
Boyle’s Law: Data Table 2
Mathematical Relationship
Between P and V
Graphical Relationship Between P and V
Pressure
(Books)
V avg.
(mL/cc)
Uncertainty
In V avg.
Average
1/V avg.
Lowest
1/ V avg.
Highest
1/ V avg.
Air
Pressure
(Books)
Total P
Total
P x V avg.
1
2
3
4
5
6
How to Find the Above
1. V avg. is the average of the three trial values for each number of books used. (3 significant digits)
2. Uncertainty in V avg. is the average of the absolute differences from the V avg.. The absolute difference
is the absolute value of the difference between the values. (3 significant digits)
3. Average 1/V avg.is the reciprocal of the V avg.. (3 significant digits)
4. Adding the Uncertainty in V avg. to the V avg. and then finding the reciprocal find Lowest 1/V avg. (3
significant digits)
5. Subtracting the Uncertainty in V avg. to the V avg. and then finding the reciprocal find Highest 1/V avg.
(3 significant digits)
6. Total P is the sum of the Pressure (books) and the Pressure Air (books).
SC6. Students will understand the effects motion of atoms and molecules in chemical and physical processes.
a. Compare and contrast atomic/molecular motion in solids, liquids, gases, and plasmas.
 You exceeded the standard(s).
 You met the standard(s).
 You did not meet the standard(s).
Boyle’s Law
Analysis
Respond in complete sentences on this paper. Show all work when performing calculations.
1.
What is Boyle’s law? What is the mathematical formula representing Boyle’s law?
2.
When you determined the Total PV in Table 1, did you obtain the same product for all trials? Explain your
response.
3.
Formulate a hypothesis to explain your response to the previous question.
4.
When you determined the Total PV in Table 2, did you obtain the same product for all trials? Explain your
response.
5.
What type of mathematical relationship exists between the variables in Boyle’s law?
6.
Scuba divers breathe compressed air. Explain why it is dangerous for divers to hold their breath while
ascending.
7.
A piston in an airtight pump withdraws so that the volume of the air chamber increases by a factor of
three. What is the change in pressure?
8.
Use the mathematical formula for Boyle’s law. In a typical automobile engine, the mixture of gasoline and
air in a cylinder compresses from 1.0 atm to 9.5 atm. If the uncompressed volume of the cylinder is 410
mL, what is the volume (in milliliters) when the mixture is fully compressed?
9.
Use the mathematical formula for Boyle’s law. What pressure is required to compress a 196.0-L sample of
air at 1.00 atm into a cylinder whose volume is 26.0 L?
10. Identify the assumptions of ideal gas behavior.
11. How would the outcome of this lab activity be different without the assumptions?
SC6. Students will understand the effects motion of atoms and molecules in chemical and physical processes.
a. Compare and contrast atomic/molecular motion in solids, liquids, gases, and plasmas.
 You exceeded the standard(s).
 You met the standard(s).
 You did not meet the standard(s).