Rainbow Test Tubes Activity

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Problem: How many colors can be created by starting with red, yellow, and blue solutions?

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Updated Jan. 10, 2017 with results:

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Results 2016-17

Materials per group of 3-4 students:

  • Student Handout RainbowTestTubesPublic (pdf)
  • Spreadsheet to collect data (excel – public)
  • 9-10 test tubes with test tube rack
  • Erlenmeyer flasks filled with red, yellow, and blue solutions of food coloring and water
    • 5 drops of food coloring per 200 mL (25 per 1L)
  • 3 x 25 mL Graduated Cylinders
  • 3 x 10 mL Graduated Cylinders
  • pipette
  • beaker filled with clean water
  • large beaker for used water
  • this activity took 2x 50 minute class periods

rainbowlabsetupflasks

This lab is an updated version of the classic Rainbow Lab (link) that has been around since the 80’s (Measuring Liquid Volume with a Graduated Cylinder 1988). I used this for many years with my 5th graders, and previously with my 6th graders in the early 2000’s. Now that I am teaching 6th grade again, I wanted to make it more open ended and challenging. The purpose of the original version of the lab was twofold: First – could they follow directions carefully to make a rainbow? Second – how precisely can they measure liquid volume?

rainbowlabsetup

For the new version of this lab, I created new objectives and assessed the students based on their problem solving, collaboration, and measuring skills.

Objectives:

  • Students will be able to precisely measure liquids with a graduated cylinder
  • Students will be able to create their own lab procedures using the given parameters to guide them
  • Students will create new mixtures and solutions
  • Students will be able to record accurate data
  • Students will collaborate and problem solve to achieve a common goal
  • Students will test, evaluate, and select the best proportions to create the colors orange, green, and purple
    • each group made 3-4 different combinations for each color and had to, as a group, determine which combinations of primary colors created the best secondary colors
  • Students will follow proper lab procedures to avoid color contamination
  • Students will record and analyze data from the whole grade and compare their findings to the averages from each group, what patterns or trends did they notice in the data?
  • Students will create their own ‘designer’ color and share it with the class
    • this was fun way to wrap up the activity, we had a ‘fashion’ show with each group coming up to the front of the room to showcase their newly created and named colors
    • if time allowed, at the end we made a rainbow with each student holding their test tube and standing next to a person who had a color similar to their own, from Red to Purple
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Visual assessment – all test tubes are even and you can quickly see that each color has a volume of 25mL.
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Sugar Density Column


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Materials

  • Student Handout (pdf)
  • Food Coloring – Red, Blue, Yellow, & Green
  • Erlenmeyer flask filled with warm tap water
  • Graduated cylinder
  • 4 Stirrers/Sticks
  • 4 Pipettes
  • 1 Spoon
  • Granulated Sugar
  • 3 Test Tubes
  • Test Tube Rack
  • 4 Clear Cups

This sugar density activity is one I have never tried before, I actually ‘borrowed’ the idea from my son’s HS Chemistry Teacher. He came home and told me they made different colored layers using only sugar, food coloring, and water. I immediately jumped on the computer and thought about how to use this in my 6th grade classes, we are in the middle of our density unit and it would be a perfect opportunity to try it out.

sugar_density_set_up
Materials for the Experiment

One of my goals for this year is re-examine my lessons and see which activities I can make more open-ended when appropriate. For this activity, most of the resources I found told the students exactly how much sugar to put in each layer and what order to place the colors into the test tube or some other type of container. I didn’t want my students to follow step by step procedures, but wanted it to be more of an exploration type of activity. I had no idea how this would turn out but gave it shot anyway.

I gave them the problem, the parameters, the tools to complete the activity, and sent them on their way. It was great to see them figure out how to solve the problem, talk out strategies, and to see them go through the trial and error process. Each group came up with a different way to solve the problem and some groups struggled more than others. I met with each group to facilitate, ask questions, and had them explain to me what they were doing and why. Overall, it was a successful lesson, they enjoyed the activity, and it really solidified their understanding of density.

I am also incorporating more open ended writing in science and I enjoyed reading their reflections about the activity.

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