Viscosity: Non-Newtonian Fluids

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DIY Experiment Series Asks: What's the g"oo"in Oobleck?

* Please click CC for closed captioning.

The "How To" From Science-U

You Will Need

  • 1 Cup Water
  • 1.5-2 Cups Corn Starch
  • Optional: Food Coloring

DirectionsKids Playing with Oobleck

  1. Put 1 cup of water in a bowl and gradually add the 1.5 cups of corn starch to it. Mix and blend very well. If it is too liquidy, add more corn starch by spoonfuls. The consistency should be somewhere between a liquid and a solid--you should be able to grab a clump using pressure to keep it “solid”, but when you open your hand it should “melt” back out like a liquid.  If desired, add a couple drops of food coloring.
  2. Play! Experiment to see when it feels most solid (hint: try punching or pounding it) and when it feels most liquid (hint: try slowly sinking an open hand into it). You can even search online for “dancing oobleck” to see what happens when sound waves are pushed through this “Non-Newtonian fluid”!

For educators and parents - How to guide young learners in science:

  • Inquiry-based learning (IBL) is a teaching approach that is fundamental for the development of higher order thinking skills (summarizing, analyzing, evaluating, creating). It puts the student in the driver's seat and promotes learning through engaging student-based investigations, following the same process used by scientists.
  • IBL begins by posing a question, problem, or scenario rather than simply presenting facts or a standard method to solve a problem. The learner is actively engaged and investigates concepts to reach authentic meaning.
  • The IBL process can vary, however the basics are as follows:

1. The student creates a testable question of their own.

2. The student obtains supporting evidence to answer the question by making observations, doing research, collecting data through an experiment, changing variables from a previous experiment, etc.

3. The student explains the evidence collected.

4. The student creates a claim (explanation) and justifies it using evidence form the investigation.

5. The student creates predictions for future investigations.

  • Recording information during the IBL process is also important to promote science literacy. The following chart is a helpful tool to guide students through the process.

Guided inquiry map

Questions to ask:

  • What happens when you change the ratio of water to cornstarch?
  • Would it still make oobleck if you use a liquid other than water? What would you use? Try it!
  • Compare Oobleck (a highly viscous Non-Newtonian Fluid) to water (a Newtonian Fluid): Put each in a cup with a hole in the bottom. Which comes out faster? What happens when you try to push the fluid through?
  • Will the Oobleck stay like this forever? What happens if you let it sit overnight? For a week?

The science behind it:

  • It’s all about viscosity, or the liquid’s resistance to flow (internal friction)! Most fluids are Newtonian (named after Isaac Newton), and will remain at the same viscosity (or rate of flow). For example, water has the same resistance/viscosity when standing in a pool as when swimming. It won’t change its internal friction or become thicker when you “shear” it (or try to move through it). Oobleck, however, is Non-Newtonian and thus changes its viscosity; if you try to move oobleck quickly (“shearing” it more), it gets more viscous, enabling the girl above to run in place on it; if you move oobleck slowly, it is more fluid and less viscous, allowing the children in the top photo to let it drip from their hands.

Resources:

  • Teaching Great Lakes Science (http://www.miseagrant.umich.edu/lessons/teacher-tools/guided-inquiry-process/)
  • Scientific American (http://www.scientificamerican.com/article/oobleck-bring-science-home/)
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