At Home With Hands On!

If We Could Turn Back Time (1/3/18)

Un-mix the Colors:

MATERIALS:

  • White Corn Syrup
  • 2 Clear Containers (one slightly taller and thinner than the other)
  • 4 Medium-sized Binder Clips
  • Liquid Food Coloring
  • Several small mixing bowls or cups
  • Water
  • Pipettes (drinking straws can also be used instead)

INSTRUCTIONS:

  1. Fill the shorter, wide Clear Container 1/3 full with White Corn Syrup.
  2. Place the taller, thin container into the container filled with syrup.  Fill the inner container with water to anchor it down.
  3. Clip three medium-sized Binder clips around the rim of the outer container, leaving an open space to add the fourth clip later.
  4. Add a small amount of either corn syrup to each of your small mixing bowls.  Stir in different colors of Liquid Food Coloring to each small bowl.
  5. Using a clean pipette for each sample (or by sucking a small amount through a drinking straw), add a small amount of colored syrup directly into the gap between the containers.  Be careful to insert the colored drops a bit below the surface of the clear syrup.
  6. Add the fourth Binder Clip to the rim of the outer container.
  7. Slowly rotate the inner container in one direction, being careful to not jostle the container back and forth inside of the syrup.  What happens to the dots of colored syrup as the inner glass is spun?  Did you expect the colors to mix inside of the container?
  8. After several spins, rotate the inner container in the opposite direction until all of the colors have separated, and have returned to their original places.  Why do the colors “un-mix”?

 

HOW DOES IT WORK:

The most commonly accepted explanation for this experiment is a phenomenon called laminar flow.  Laminar flow happens when a fluid moves in thin sheets or layers that glide alongside each other, but never actually mix together.  As the inner container is rotated, the sticky (or viscous) fluid will begin to twist after it, one layer at a time.  As the layers of dyed syrup remain separate within their original layers of syrup, the dots will appear to stretch and blend together; however, the layers of color are simply overlapping, giving the appearance of blending together!  From the side, the overlapping layers of colors give the appearance of mixing together.  But if you look downward into the gap between the two containers, you will actually see how the thin layers have rotated, but not actually mixed together!

un-mix_the_colors_2

When you rotate the inner glass in the other direction, the layers of fluid simply twist back until the layers of colored syrup all line up in their original formation.

THE MORE YOU KNOW:

When you turn on the kitchen faucet at home, you might notice a lot of ripples or bumps in the stream of water—maybe some water droplets even jump out of the stream!  This is because the water is very likely moving in a turbulent flow.  Turbulent flow is characterized by an uneven flow of liquid, causing small swirls and ripples within the stream.

flow

There are special faucet attachments that can create a more stable Laminar Flow stream of water. These faucets produce very clear and glass-like water streams that are often used in decorative fountains and even in amusement park water displays!

GOING ONE STEP FURTHER:

  1. Repeat the experiment using a different viscous substance.  You could try using vegetable glycerin, coconut oil, or even a clear liquid hand soap.  Which substance creates the best “un-mixing” result?  Do the less-sticky substances work better, or the more-sticky substances?
  2. Repeat the experiment using MULTIPLE viscous substances.  For example: You might fill the outer container 1/3 full of vegetable glycerin, but insert drops of colored liquid hand soap!  If the dyed droplets have a different viscosity than the substance around them, will the colors ever fully “un-mix”?
  3. You can completely change the experiment to test a Turbulent Flow.  Instead of using an inner container to twist the fluid, simply mix the dots of dyed syrup with a kitchen spoon.  Once the colors are thoroughly mixed, can you “un-mix” them?  Why or why not?

Happy New Year, science friends! Just go with the (laminar) flow!