Liquid or solid?

You probably already know that matter exists in 3 states: solid, liquid and gas. But what happens when something is only a liquid sometimes? Play around with this mixture and find out!

Materials:

water
cornstarch
large bowl
newspaper or paper towels to keep the area clean

Try it out:

1. In a large bowl, measure out a cupful of cornstarch.
2. slowly add an equal amount of water to the mixture. Mix it up with your fingers.
3. Keep mixing and adding water until the mixture is smooth.
4. Try pouring the mixture. Does it pour like a liquid?
5. Next try rolling it into a ball. Can you do it? What happens when you stop rolling?
6. Try poking the mixture really fast and slowly. Can you feel a difference?
7. Play around with the mixture as much as you want! To clean up, just rinse your hands in warm water and throw the mixture in the trash.

What's happening

The cornstarch and water mixture is an example of a non-newtonian fluid. Non-newtonian fluids are strange substances that act like liquids sometimes and solids at other times. For example, it pours like a liquid but when you poke it or roll it into a ball, it feels like a solid.

This mixture isn't a liquid at all. It's a suspension. That means the little pieces of cornstarch are floating around in the water instead of being dissolved. When you apply a large amount of pressure, like when you poke the mixture, the cornstarch pieces stick together and act like a solid. But when you allow them to flow slowly, they move with the water.

If you thought this was cool...

This experiment is related to a part of physics called fluid mechanics. Fluid mechanics is important for many types of engineering, including aerospace engineering, chemical engineering, and civil engineering. You can find out more here.