- Large tub or other container.
- Cornstarch (2-3 pounds)
- Measuring cup
- Liquid measure
- Stirring device (big spoon)
- Deck of cards
- Wooden platform
States of Matter
Begin by showing solid liquid and gaseous matter. Review the states and their properties.
Is that all there is? Are there things in between?
How about something between a solid and a liquid? Lets be good scientists and follow a recipe.
1 cup water 2 cups cornstarch
Mix these together in a large container.
- How does the mixture respond to moving the stirrer?
- How does the response change when the stick moves fast, what about when it moves slow?
- What does the mixture do when you pick it up? Squeeze it hard, and squeeze it soft.
- How is this like a liquid? How is this like a gas?
- Could this be useful for anything?
Demonstrate with a deck of cards the difference between normal and shear stresses.
- In terms of the deck of the cards, explain what happens when the cornstarch mixture is sheared.
- What is the opposite of the cornstarch.
The opposite of shear thickening is shear thinning. The material gets easier to deform as the stress increases.
Ketchup does this. Demonstrate with the bottle of ketchup, and then on incline.
Add water to ketchup.
- How can you tell shear thinning is taking place?
- Is there an end to the thinning?
Back to the ice block...
How it Matters in Ice Dynamics
Ice is a shear thinning substance. To understand its flow, we must understand the mathematics of shear thinning.