Materials Included In Kit

Additional Materials Required

Safety Precautions

Although the materials in this lab are considered nonhazardous, please observe all normal laboratory safety precautions. Remind students to wear goggles or safety glasses whenever working with chemicals or glassware in the lab. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulation that may apply, before proceeding. Each sugar solution may be disposed of down the drain with plenty of cold running water according to Flinn Suggested Disposal Method #26b.

Teacher Tips

• Be sure the students have the correct set-up and are adding each solution to their column slowly. If they add the solutions too quickly, the layers will mix!
• Leave a small amount of liquid in the funnel between adding each layer to prevent air bubbles from forming and disturbing the layers.
• Make this lab open inquiry by showing the students a sample of a column and instruct them to create their own using just water, sugar and food dye.
• Don’t limit students’ creativity! Have them vote for their favorite column at the end of the lab.
• To further challenge your students, have them create a tower with more layers.
• For lighter food coloring, prepare a stock of each solution. For example, to make a light purple, add one drop of red and two drops of blue to a 1000-mL beaker and fill the beaker to the 800 mL line. The more dilute the food coloring, the lighter the color!

Sample Data

Procedure

1. Set down six 150-mL beakers and label 1–6.
2. Fill the first beaker to 100 mL with deionized or distilled water.
3. Mass 12 g of sugar and add to the second beaker. Fill the beaker to ~80 mL with deionized or distilled water and stir to dissolve. Once the sugar has dissolved, bring the solution up to 100 mL.
4. Mass 24 g of sugar and add to the third beaker. Fill the beaker to ~80 mL with deionized or distilled water and stir to dissolve. Once the sugar has dissolved, bring the solution up to 100 mL.
5. Mass 36 g of sugar and add to the fourth beaker. Fill the beaker to ~80 mL with deionized or distilled water and stir to dissolve. Once the sugar has dissolved, bring the solution up to 100 mL.
6. Mass 48 g of sugar and add to the third beaker. Fill the beaker to ~80 mL with deionized or distilled water and stir to dissolve. Once the sugar has dissolved, bring the solution up to 100 mL.
7. Mass 60 g of sugar and add to the third beaker. Fill the beaker to ~80 mL with deionized or distilled water and stir to dissolve. Once the sugar has dissolved, bring the solution up to 100 mL.
8. Color the solutions! Hint: do not color them all the same or you will not be able to see the layers. In addition, layers that are next to each other should be different colors.
9. Set up the column and separatory funnel as shown in Figure 1.
   {14114_Procedure_Figure_1}
10. Pour the contents of the first beaker into the separatory funnel. Open the stopcock and allow the solution to fill the column. When there is a small amount left in the tip of the funnel, close the stopcock.
11. Continue to add the solutions, from least dense to most dense, very slowly to the column. Each time there is a small amount of liquid left in the top of the funnel, close the stopcock.
12. Once all the solutions have been added to the column, slowly pull the tubing out of the column. Hint: this step must be done carefully to avoid mixing the layers.

Introduction

Challenge your creativity by creating a sweet tower of color using just three ingredients: water, food dye and sugar. Mix the ingredients in varying ratios to produce solutions of different density and color.

Concepts

• Solutions
• Density

Background

Density is a physical property of a substance that describes the relationship between the mass of the substance and how much space the substance takes up. In other words, density is the mass of a substance per unit volume, as seen in the following equation.

Density and mass are directly proportional when volume remains constant. By increasing the mass of a substance, the density will also increase. For example, consider two 150-mL beakers containing different amounts of salt salt. One beaker has 10 g of salt, and the other beaker has 50 g of salt. Each beaker has a total solution volume of 100 mL. The solution with only 10 g of salt is less dense than the solution with 50 g of salt as they have the same volume but different masses.

Given this information, you will be challenged to create solutions of varying density using only three components: sugar, water and food dye. This activity will encourage you to use experimental design to develop a column composed of six different layers. Experimental design is the process of planning an experiment that meets specific goals or certain objectives. The aim is to encourage you to use your critical thinking skills and the scientific method to predict an outcome with a hypothesis, create a procedure to test this hypothesis and explain or describe the observations gathered from testing the hypothesis.

Experiment Overview

The purpose of this activity is to use creativity and knowledge of density and aqueous solution preparation to create a colorful tower using only three ingredients. Each group of students will be responsible for developing a hypothesis and designing a procedure to produce a tower with six different layers.

Materials

Safety Precautions

Although the materials in this lab are considered nonhazardous, please observe all normal laboratory safety precautions. Wear goggles or safety glasses whenever working with chemicals or glassware in the lab. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Form a working group of 2–3 students to design a colorful column (composed of six distinct layers) from the materials provided. Use the following prompts and questions to guide your design of the column.

1. Define density.
2. Which of the following two solutions would you expect to be the densest: a) 5 g of sugar dissolved in enough water to make 50 mL of solution or b) 30 g of sugar dissolved in enough water to make 50 mL of solution? Predict and explain.
3. Prepare and weigh the two solutions, and calculate their densities. Which is the densest?
4. What happens when a very dense object is placed in a liquid that is less dense? For example, does a piece of iron sink or float in water?
5. By extension, what do you think will happen if you add slowly and carefully (using a separatory funnel attached to a length of tubing) the solution prepared in step 2b to the solution prepared in step 2a? (Note that you are adding the more dense solution to the least dense solution, or layering from least dense to most dense).
6. Carefully test your hypothesis by first adding solution 2a to a cylinder. Next, slowly and carefully add solution 2b to the graduated cylinder according to the following method:
   1. Set up the apparatus shown in Figure 1.
      {14114_Procedure_Figure_1}
   2. Pour the solution from 2a into the separatory funnel.
   3. Open the stopcock and slowly add the solution to the column.
   4. When a small amount of solution is still in the funnel, close the stopcock.
   5. Add the solution from 2b to the separatory funnel.
   6. Open the stopcock and slowly add the solution to the column.
7. How many different solutions (with unique densities) do you need to prepare to make a colorful column composed of six layers?
8. Prepare the number of solutions determined in step 7. Keep the total solution volume constant for all solutions and vary only the mass of sugar added. Be sure to fully dissolve all of the sugar into solution. A magnetic stir plate can help with this process. Use food coloring to vary the colors of the layers to design the most vibrant column possible!(Hint: Be sure to vary the densities by at least 10%. That is, be sure to vary the amount of sugar added to successive layers by at least 10 g assuming a total solution volume of 100 mL).
9. Using the same method described in step 6, prepare your column.
10. Consult your instructor for proper disposal of your solutions.