Explore Color Science with Grape Juice

What You Need:

  • Frozen concentrated grape juice in a pitcher or other container
  • Science Journal or lined paper to record steps and observations
  • Pencil
  • Crayons
  • Water
  • Vinegar
  • A stirring spoon
  • Soap
  • Jars or glasses
  • Baking soda
  • Lemon juice

What You Do:

  1. In advance, thaw the frozen grape juice and mix it with an equal amount of water in a pitcher.
  2. Give her some grape juice in two jars or glasses. Explain that she will be experimenting to see if she can make the purple grape juice change color. It will look like a magic trick, but it's really a chemical reaction: a change that takes place when certain substances come into contact with one another.
  3. Have her pour a little lemon juice into one of the glasses filled with grape juice. In her Science Journal or on the sheet of paper, help her record what she mixed together (grape juice and lemon juice) and then have her record what happened. Have her draw a picture of what she saw. 
  4. Explain to her that the lemon juice is an acid. All acids will turn a blue liquid or indicator, red. Tell her that the grape juice is called an indicator because it will indicate (or tell) whether another liquid is an acid.
  5. Next, add two spoons of baking soda to the second glass or jar of grape juice. Again, have her record what she mixed together as well as the results. This time the grape juice should turn green. 
  6. Explain to her that the baking soda is the opposite of an acid. It is what is known as a base.  A base will change the color of an indicator from blue to green.
  7. Now, see what happens if you add some baking soda to the red liquid (the grape juice and lemon juice). It should change back to purple—the indicator color for neutral. Ask her what she thinks would happen if lemon juice was added to the green liquid?  Make sure she doesn't drink the grape juice she's been experimenting with, or she will be in for a not-so-tasty treat!

 Extension Activities:

  1. Empty the two glasses of juice you and your child have been experimenting with and pour fresh grape juice into each one. Let her experiment with vinegar and soap (dish soap works fine) to determine which is an acid and which is a base, based on the color that each turns the grape juice. Continued experimentation will allow her to build on what she learned from the previous experiment with the lemon juice and baking soda.
  2. Flowers called hydrangeas produce blue flowers when planted in acidic soil, but pink flowers when planted in a basic soil. Adding an acid or base to the soil can make the flowers change from one color to the other. If you have a hydrangea in your yard, try this experiment!

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