Density Lab
OBJECTIVES: 1. Measure the mass and volume of water and a rubber stopper.
2. Calculate the density of water and a rubber stopper
3. Compare the densities of distilled water with water of different salinities.
HYPOTHESIS: Develop a hypothesis on the following question:
1) What will happen to the density of water as its salinity increases?
MATERIALS:
100 mL graduated cylinder
balance
Dropper pipette
2 Beakers
distilled water
#2 rubber stopper (solid)
Salinity samples
PRE-LAB QUESTIONS:
1. Define density in your own words.
2. Write the formula for calculating density mathematically. What units are usually associated with density?
3. A piece of metal with a mass of 15.45g is added to 21.27mL of water in a graduated cylinder. The water level
rises to 24.78mL. Calculate the density of this metal.
4. Acetone, a common solvent, has a density of 0.79 g/mL at 20˚C. What is the volume of 100.g of acetone at
20˚C?
5. What method will you use to find the density of the rubber stopper?
PROCEDURE:
Part A. Density of distilled water
1. Find the mass of a clean and dry 100-mL graduated cylinder. Record this
mass in Data Table 1.
2. Measure out 20-50mL of water and record exact volume.
3. Mass the cylinder and water.
4. Calculate and record the mass of the water.
5. Use a thermometer and record the temperature of the water.
6. Calculate the density of the distilled water and record.
Data Table 1: Part A: Density of Distilled Water
Mass of empty graduated cylinder (g)
Mass of graduated cylinder and water (g)
Mass of water (g)
Temperature of water (oC)
Volume of water (mL)
Density of water (g/mL)
Part B. Density of a #2 rubber stopper
1. Find the mass of the rubber stopper. Record the mass in Data Table 2.
2. Pour about 50-mL of tap water into the 100-mL graduated cylinder. Read
and record the exact volume.
3. Carefully place the rubber stopper into the graduated cylinder. Make
sure that it is completely submerged. (You might want to use a pencil
or stirring rod to hold the stopper just under the surface.)
4. Read and record the exact volume.
5. Mathematically find the volume of the rubber stopper and its density.
Data Table 2: Part B: Density of Rubber Stopper
Mass of rubber stopper (g)
Initial volume of water in cylinder (mL)
Final volume of water in cylinder (mL)
Volume of rubber stopper (mL)
Density of rubber stopper (g/mL)
Part C. Density of salt water samples
1. Find the mass of a clean and dry 100-mL graduated cylinder. Record this
mass in Data Table 1.
2. Pour salt water sample A into the graduated cylinder and record the volume.
3. Mass the cylinder and salt water.
4. Calculate and record the mass of the salt water.
5. Calculate the density of salt water sample A and record.
6. Repeat the procedure for salt water samples B and C.
Data Table 3:
Part C: Density of Salt Water Samples A, B, C
A 1%
B 15%
Mass of empty graduated cylinder (g)
Mass of graduated cylinder and water (g)
Mass of water (g)
Volume of water (mL)
Density of water (g/mL)
C 30%
Graphical Analysis
Create a line graph to compare density (X-axis) and salinity (Y-axis) of your water samples. Be sure to
include the density of distilled water in your graph.
Post Lab Questions
1. Use the accepted values given by your teacher to help you determine your percent error for the density of
water. Use the following equation to calculate and show your work!
% Error = (actual value – experimental value) X 100
Actual value
2. Explain what happens to the density of water as its temperature increases and decreases and why it is
important to record temperature at which density is measured.
3. Explain what happens to the density of water as the salinity increases. Explain why this happens.
Conclusion: Be sure to restate the purpose and briefly describe what you learned in the lab. The acceptable range
for % error is less than 10%. In your conclusion, state whether or not your % error was acceptable. If it wasn’t,
explain what could have caused the discrepancies. Explain why it is important to take the temperature of a sample
when determining the density. Finally, explain to me why it is easier to float in the Dead Sea rather than in a pool.