Concluding a two-part lab activity, students use triple balance beams and graduated cylinders to take measurements and calculate densities of several household liquids and compare them to the densities of irregularly shaped objects (as determined in Part 1). Then they create density columns with the three liquids and four solid items to test their calculations and predictions of the different densities. Once their density columns are complete, students determine the effect of adding detergent to the columns. After this activity, present the associated Density & Miscibility lesson for a discussion about why the column layers do not mix.
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- Common Core State Standards for Mathematics: Math
- 3. Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6)  ...show
- International Technology and Engineering Educators Association: Technology
- F. Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. (Grades 6 - 8)  ...show
- Missouri: Math
- Missouri: Science
- 1. Science understanding is developed through the use of science process skills, scientific knowledge, scientific investigation, reasoning, and critical thinking (Grades 0 - 8)  ...show
- Explain the difference and relationship between mass and density.
- Take accurate measurements of mass and volume using a triple balance beam and reading a meniscus, respectively.
- Relate hydrophobicity and miscibility to density.
- triple balance beam
- 2 100-ml graduated cylinders
- Popsicle® or wooden craft stick piece (break wooden sticks into 1-inch pieces)
- crayon piece (break crayons into 1-inch pieces)
- pasta noodle (such as dry, uncooked penne pasta)
- tap water, 30 ml
- (optional, but recommended) few drops of liquid food coloring (to color the water)
- corn syrup, 30 ml
- vegetable oil, 30 ml
- 4 paper cups, 5-ounce (~ 148 ml) size
- liquid laundry or dish detergent, ~1 cup
- Density Column Lab - Part 2 Worksheet, one per student
|density:||Mass per unit volume.|
|hydrophobic:||Water-fearing or water-hating.|
|immiscible:||Incapable of mixing.|
|miscible:||Capable of mixing.|
Before the Activity
- Gather materials and make copies of the Density Column Lab – Part 2 Worksheet.
- Break the Popsicle sticks and crayons into three or four equally sized pieces so that the pieces fit into graduated cylinders. At each lab station, place a marble, Popsicle stick piece, crayon piece and pasta noodle.
- Prepare and place at each lab station paper cups filled with water, vegetable oil, corn syrup and detergent. Recommendation: Add a few drops of food coloring to the water to help distinguish it from the other liquids.
With the Students
- Divide the class into groups of five students each (same groups as in the associated Part 1 activity).
- Hand out the lab worksheets and have students document their density predictions for the three liquids.
- Direct students to fill in the worksheet data table with information learned from the previous lab activity (densities of four solid objects).
- Ask students how they predict the densities of the liquids will compare to the solids. Direct them to draw on the back of their worksheets a diagram that ranks their predictions for the densities of all seven items (three liquids and four solids) in relation to each other.
- Measure the mass of an empty graduated cylinder and record this value for each of three liquids in the data table.
- Next, add 30ml of one of the liquids (best to start with the corn syrup) into one of the graduated cylinders. (As necessary, guide students on how to read the liquid level in the graduated cylinder; explain about the meniscus.) Record the exact volume and the mass of the graduated cylinder with the liquid. Subtract the two masses to obtain the mass of the liquid. Leave this liquid in this graduated cylinder to build the column.
- Next add 30ml of another liquid into the second graduated cylinder. Record the exact volume. Measure the mass of this graduated cylinder with the second liquid, record the mass and then calculate the mass of the second liquid.
- Add this second liquid to the first graduated cylinder containing the first liquid. Then rinse and dry the now emptied graduated cylinder.
- Repeat this process for the last liquid and then calculate the densities of all three liquids. Record on the worksheet.
- Slowly and one at a time, add the four solid items in the density column just created. Draw a diagram of the actual density column on the back of the worksheet, showing the relative placement of all liquids and solid objects relative to each other.
- Finally, add liquid detergent to fill the graduated cylinder, being careful not to overflow. Watch what happens and record your observations on the worksheet. (The layers mix without any stirring.)
- Have students answer the questions on their worksheets and hand them in for grading.
- Conclude by leading a wrap-up class discussion to compare results and conclusions; see questions in the Assessment section.
Activity Embedded Assessment
- What is the density of water? (Answer: 1,000 kg/m3 or 1 g/mL or ~8.3 lbs. per gallon.)
- How do we determine the mass and volume of one of the liquids? (Answer: For each liquid, we measure the volume using a graduated cylinder. Then we place the graduated cylinder on the triple balance beam and record the mass of both the graduated cylinder and the liquid. Finally, we subtract the mass of the graduated cylinder to find the mass of the liquid.)
- What are common uses for detergent? What do you think will happen once you add it to the column? (Answer: Detergent breaks down grease and fat, as well as disinfects. Student predictions will vary. The science behind what happens is explained in detail in the associated lesson.)
Comparing the density of different liquids: How do the densities of vegetable oil, water and corn syrup help them to form layers in a cup? Published 2007. Activity 7.3, Investigation 7: Density, Inquiry in Action, American Chemical Society. 2007. Last accessed 2010. (Inspiration for this activity) http://www.inquiryinaction.org/pdf/chapter7/7.3_teacher.pdf
Jessica Ray, Phyllis Balcerzak, Barry Williams
© 2013 by Regents of the University of Colorado; original © 2010 Washington University in St. Louis
GK-12 Program, School of Engineering and Applied Science, Washington University in St. Louis
Last modified: March 4, 2015