The image below is what an inverse relationship looks like when the two
variables are graphed.
Instructions: Record the answers to the questions below in your lab packet.
- Create a graph for each set of data you collected. When you are finished
compare them with the one here.
- Does the general shape of your graphs stay the same
- What conclusion can you make from comparing your graphs with each other
Scientists can learn more about how gases behave by analyzing the mathematical
patterns in the numbers. In your lab packet record the answers to the questions
below. Return to one of your data tables and see if you can find any additional
patterns from the numbers.
- Draw a third column on your data table to the right of the
Pressure column,and label it P x V.
- Multiply all the pairs of pressure and volume
values and put them in your new column.
- What do you notice about all of the products you have
- Check with your classmates on their results. How are they the
same? How are they different? Can you explain the differences?
Let's go back to the first data table in which you created the P x V
column. If any pair of pressure and
volume values multiplied together
always give the same constant value, then we ought to be able to make
a mathematical relationship.
P1 and V1 represent the first set of conditions and
P2 and V2 represent the second set of conditions.
This mathematical relationship is called Boyle's Law (Remember Robert
Boyle?). This relationship is only true if
we use data collected at the same temperature.
Volume of a gas is always equal to a constant value dependent on
This relationship allows us to do a problem like the following:
If the pressure of 3.5 Liters
of air inside a volleyball is 800 mm Hg,
and someone hits the ball during a serve and causes the
volume to momentarily decrease
to 3.0 Liters, what will be the new
pressure during that
Additional Analysis Questons
- During the up-stroke of the piston of a lawn mower engine, the
inside is greatly reduced. What effect does this have on
of the gases inside?
- You repaired a leak in your bike tire and your friend offered to let
you connect a hose from one of his tires to the repaired tire. From
what you have learned in this lesson would you expect to be able to
inflate your tire? Give your reasons.
Gases have been scientifically investigated for years, starting with
Robert Boyle's work in the 1600's. Robert
Boyle did many experiments with gases, and is well known for his
discovery of "Boyle's Law." The work of Robert Boyle and other scientists
led to the "Gas Laws."