Sweet and Colorful Density Column
The density of a solution is directly proportional to the concentration of dissolved solute. By determining the mass of different solutions with similar volumes, students can calculate the density of the solutions. Solutions that are less dense can “float” on top of solutions that are more so. After determining the density of each solution, students will build their own density column to demonstrate their understanding of these concepts.
Materials (per class)
- Tap Water, 3 L
- Long-Handled Spoon (item #115507 or similar)
- Granulated White Sugar, 2-1/2 lb
- 6 Large Plastic or Glass Containers (500 mL or larger, similar to item #113111)
- 6 Colors of Unsweetened Powdered Drink Mix (suggested colors and flavors: red—cherry, orange—orange, yellow—lemonade, green—lemon lime, blue—berry blue, purple—grape)
Materials (per group)
- Graduated Cylinder, 10 mL (item #721615)
- Graduated Cylinder, 25 mL (item #721616)
- Wash Bottle with Water for Rinsing (item #716592)
- Electronic Balance (readable to 0.1 g, item #702357)
- 6 Disposable Pipets (item #736984)
- Paper Towels (item #633954)
- Waste Container (item #721207 or similar)
- The instructions that follow explain how to prepare solutions that will create a multilayered density column. The prepared solutions will be labeled in a way that prevents students from predicting what order they should be placed in the density column.
- Label 6 large plastic or glass containers (500 mL or larger) using letters A to F.
- Prepare the mass-by-mass percentage of sugar solutions in the table above by mixing the indicated mass of sucrose with 500 mL (500 g) of distilled water in the appropriately labeled container.
- Match each package of powdered drink mix to the appropriately labeled container. Add 1 g of the appropriate powdered drink mix to the sugar solution in each container.
- Use a long-handled spoon to stir the contents of each container until all of the sugar and powdered drink mix dissolves. Note: It may be difficult to dissolve all sugar in some solutions. You may wish to stir each solution thoroughly, wait 30 minutes, and stir again. Continue stirring once every 30 minutes until all sugar and powdered drink mix dissolves.
- (optional) If the solutions will not be used right away, use a cover to seal each container. If necessary, solutions can be stored in covered containers for a week or more.
- Place the 10-mL graduated cylinder on the balance, and tare the balance. The balance should now read 0.0 g.
- Remove the graduated cylinder from the balance and place it on the lab bench.
- Pour 5 mL of Solution A into the 10-mL graduated cylinder. Record the volume to the nearest 0.1 mL.
- Place the 10-mL graduated cylinder containing Solution A on the balance. Record the mass of Solution A.
- Pour the solution into the waste container. Rinse the graduated cylinder and dry it by tapping it gently on a paper towel.
- Repeat the preceding steps, finding the volume and mass of all the remaining solutions.
- Calculate the density of each solution by dividing the mass of each liquid by the volume measured.
- Based on the densities you calculated in the preceding step, list the solutions in order from most dense to least dense.
- Prepare a colored density column in the 25-mL graduated cylinder.
- Use the 10-mL graduated cylinder to measure about 5 mL of the solution with the greatest density.
- Prepare to pour the solution from the 10-mL graduated cylinder into the 25-mL graduated cylinder. Tilt the 25-mL cylinder and pour the liquid so that it slowly runs down the side.
- Repeat steps 9a and 9b with each additional solution, in order of decreasing density.