Non-Newtonian Fluid-OOBLECK (Carol Cao)

Author

Carol Cao

Principle(s) Illustrated

1. States of Matter

2. Bonding Patterns

3. Non-Newtonian Fluid

4. Newton's "rules" for "normal" fluids: According to Sir Isaac Newton who described how fluids behave, there are general "rules" for how "normal" fluids- such as water and gas- behave. One such rule is viscosity (or how fluids flow) and normal fluids have a consistent viscosity (or flow)

5. There are fluids in existence that do not follow Newton's "rules" for viscosity. These fluids are called non- Newtonian fluids

6. Examples of non-Newtonian fluids may include ketchup, blood, and the mixture of cornstarch and water.

Standards

• Physics Science Standards (Motion and Force)-

  • 1. Students know that when forces are balanced, no acceleration occurs; thus an object continues to move at a constant speed or stays at rest (Newton's first law).

    2. Students know how to apply the law F=ma to solve one-dimensional motion problems that involve constant forces (Newton's second law).

• Chemistry Standard-

  • 1. Students know the random motion of molecules and their collisions with a surface create the observable pressure on that surface.

• Disciplinary Core Idea: MS P.S. 1-1: http://www.nap.edu/openbook.php?record_id=13165&page=106

• Cross-cutting Concepts: MS PS 1-4: http://www.nap.edu/openbook.php?record_id=13165&page=87

Questioning Script

Prior knowledge & experience:

• States of matter: Solid, Liquid, and Gases

  • • Students understand and know how most normal fluids behave and how viscosity is constant with "normal" fluids- such as water and gases.

    • Students may know how to describe Newton's law of viscosity and identity characteristics of fluids that follow the laws.

Root question:

Describe the following substance in terms of states of matter and molecular movement. What do you notice when you try to pick it up? What happens when you try to push down on the substance? Can you explain what is happening?

Compare two fluids: Newtonian and non-Newtonian:

Predict How will fluid A (water) behave when we stir it with a spoon?

How will fluid B (mixture of water and cornstarch) behave when we...

• Stir it with a spoon?

• Rest our hand on top?

• Drop a ball on it?

• Hit the surface with a hammer?

Target response:

Students will describe that when they try to push down on the substance, it doesn't move, but it can be poured out of the contain and have liquid qualities. The substance also can break into pieces, like in solids. The viscosity is not independent of shear rate.

Since Fluid B is a non-Newtonian fluid, it does not follow all of Newton's "rules" for "normal" fluids. Fluid B is still a fluid, however it displays some unique properties such as responding to blunt forces (hitting with a hand or hammer) and acting similar to a solid. In addition, fluid B does flow like "normal" fluids and solid objects that are more dense then fluid B will sink beneath.

When you quickly stir or hit the fluid (of cornstarch and water) you are applying what a physicist would call "sideways shearing force" to the water. In response, the water shears, or moves out of the way. The behavior of Ooze relates to its viscosity, or resistance to flow. Water's viscosity doesn't change when you apply a shearing force--but the viscosity of your Ooze does.

Common Misconceptions:

Many students can't explain what is happening. They think it's a combination of a liquid and a solid.

Fluid B (mixture of cornstarch and water) is both a solid and a liquid. The mixture changes between states of matter.

Photographs and Movies

References

Non-Newtonian Fluid (Wiki)

Oobleck Instructions

Non-Newtonian Fluid (Article)

Reference 1: Science Learning gives a clear overview and explanation for students to learn about non- Newtonian fluids.

Reference 2: University professor explains Newton's Laws of viscosity and goes over the various types or classifications for fluids and non- Newtonian fluids.

Reference 3: A. Good Discovery Channel TV show explanation for cornstarch and water mixtures and non-Newtonian fluids via You Tube

Reference 4: An explanation from Popular Mechanics

Reference 5: The Exploratorium's explanation and guide to making the mixture of cornstarch and water https://www.exploratorium.edu/science_explorer/ooze.html