Title: Density of Marbles and Other Objects

Purpose:

• to determine the density of several objects
• to use the water replacement method to determine volume
• to use a balance to determine mass

Materials:

• cylindrical objects
• spherical objects (marbles)
• irregular objects
  

Procedure:

1. Be careful when placing samples into glass graduated cylinders
2. Using the balance, determine and record the mass of each samples (to within 0.01 g)
3. Fill the graduated cylinder with about 8 ± 1 mL water
4. Tap the cylinder gently to make sure that no air bubbles are stuck to the sides
5. Read the water level on the graduated cylinder to ± 0.1 mL and record
6. Carefully place one of the objects into the cylinder
7. Reread the water level and record
8. Remove the item and water
9. Repeat steps 2~7 for the remaining objects
10. Clean up and dry all equipment and materials
    
    

Results: (Observations and data~~~data charts and graphs and calculations where appropriate. Organization is necessary)

DATA: Results should be recorded in a data table similar to the following:

(USE A RULER: NEATNESS COUNTS)

Object	Mass (g)	Water level without object A	Water level with object B	Volume of Object (B - A)
marble 1	g	mL	mL	mL
marble 2	g	mL	mL	mL
plastic cylinder	g	mL	mL	mL
etc	g	mL	mL	mL

CALCULATIONS:

Notice that the calculations below are organized in a very specific pattern.

• Make everything NEAT, CLEAN, and LOGICAL
• Record the calculations in data chart format!

• Determine the Volume of each object and record in data chart above
• Compute the density of each object (use the formula D = m/V)
• Compute the average density of each type of item:
  • Gather data from classmates if necessary
• Avg Density (g/mL) = [sum of all densities (g/mL)] / number of objects tested
• Compute the percent error for each type of object
  • formula: (A - O/A) x 100
• obtain the actual value (A) from the teacher
• use your average density values as the observed values (O)
• Record the results in a data chart (Example follows)
  
  

Discussion:

1. Summarize what you did
2. Discuss sources of error....(This error analysis is one of the most important portions of a lab activity.
   • For this lab, list all possible sources of error which you cannot control in your procedure, observations, and measurements.
   • DO NOT include computational or performance errors such as not pressing the right calculator buttons, misreading instructions, misreading your data table, your lab partner....these are controllable!)
3. Describe the limitations of this method: what types of objects/substances could not have their densities determined using the water replacement method?
4. Comment on the accuracy and precision of the volume measurement made in the 10 mL graduated cylinder vs. the 25 mL graduated cylinder.

Conclusion: (A one sentence testable statement that follows from your results, what you did, what you observed)

for this lab you may want to compare the density values of different objects