Lab: Boyle’s Law
In this lab you will explore the relationship between the pressure exerted on a gas and it’s volume.
Mathematically this relationship can be expressed as an indirect relationship (as one variable increases or
decreases the other does the opposite). Specifically the relationship (now take a breath before you read
this… and read it again and again until you get it!) can be stated like this: the volume that a gas occupies is
inversely proportional to the pressure exerted on the gas. The equation looks like this P*V=K for a given
mass of gas at a temperature that doesn’t change. The K in this equation represents a constant and we will
often use a form of this equation as follows; P 1*V1 = P2*V2.
Materials:
Thin stem micropipette
Colored water
Laboratory Burner
Pliers or crucible tongs
Procedure:
1.
2.
3.
4.
5.
Fill a thin stem micropipette with colored water. Make sure the bulb part is filled (the bulb!!… the
part at the bottom! not the stem)
Seal the end by placing it in a burner flame and just when it begins to melt squeeze the end shut
with a pliers or crucible tongs.
Put the sealed pipette on the lab table and record the length (in mm) of the trapped air column.
Once you have recorded the length of the column then begin placing books (of equal size.. chem.
texts are a good choice) one at a time on the bulb. Design a data table that includes the size of the
air column in relation to the number of books. You should have at least five readings each with a
different number of books.
Prepare a graph with the independent variable on the x-axis and the dependent variable on the
Y-axis. The # of books would equal the pressure variable and the volume variable would be the
length of the air column in millimeters.
Questions:
1.
2.
3.
What is an independent variable and what is a dependent variable (in general that is, not
specifically as relates to the pressure and volume variables of this lab)?
Does your graph show the expected relationship between the pressure exerted on the air column
and the volume of the trapped air column?
Using the kinetic molecular theory, explain the observed behavior of gases (the trapped air
column) in this experiment.
dstreib: microscale lab – Boyle’s law
dstreib: microscale lab – Boyle’s law