What’s That Liquid?
An Exercise in Density and Graphing
8th Science
PURPOSE:
The student will measure the mass of several volumes of a liquid and graph the data. The
graphed data will tell them the density of the liquid.
MATERIALS:
Graduated cylinder
Balance
Disposable Transfer Pipet
Unknown liquid
Safety Goggles
PROCEDURE:
1. On a separate sheet of notebook paper, write a hypothesis statement relating how the mass
values will change with added volume. Your data chart will also go here.
2. Put on your goggles.
3. Collect data.
a. Use the disposable pipet to transfer 2.0 mL of liquid into the graduated cylinder. Be
sure that you read the graduated cylinder with your eyes even with the bottom of the
meniscus.
b. Place the graduated cylinder on the balance. Record the mass on a data table that
you will create.
c. Remove the graduated cylinder from the balance and transfer 2.0 more mL of the
liquid to the graduated cylinder. Return it to the balance and weight. Record the
mass on your data table.
d. Continue adding the liquid in 2.0mL increments and reading the mass until a total of
10.0 mL of liquid has been transferred.
e. Dispose of the liquid as instructed by your teacher. Wash the graduated cylinder
with ample water and clean up any spills which may have occurred during the lab.
f. Wash your hands.
4. Make a graph using your mass and volume data. What variable will be on the X axis and
what variable will be on the Y axis?
CONCLUSION AND QUESTIONS:
1. What is the slope of the line? Show you calculations.
2. What are the units for the slope?
3. Write the equation of the line determined by the data.
4. What is the value of the Y-intercept? What does it represent?
5. Your equation is in the slope-intercept form (y = mx + b). Re-write the equation with words
for y, a, x, and b. (Hint: What is on the Y axis?)
6. What would be the mass of the liquid and graduated cylinder if you have 7.5 mL of liquid in
the cylinder?
7. If you have 6.0 g of the liquid, how many mL of liquid should you put in the cylinder?
8. Identify your liquid, using the list I provide.
9. A student reads the graduated cylinder at the top of the meniscus each time, rather than at
the bottom of the meniscus. How would this error affect your calculated density? State clearly
whether the density would increase, decrease, or remain the same and must be justified.