The March STEM Challenge of the Month is in honor or Dr. Seuss’s birthday on March 2nd. While Dr. Seuss is best known for Green Eggs and Ham or The Grinch, he also gave name to the gooey, part liquid/part solid substance called oobleck in his book Bartholomew and the Oobleck. Your daughter may have made oobleck at school or at home but have you ever thought about the science behind this strange material? Let’s examine that a bit more in March’s STEM Challenge of the Month!
Oobleck : Is it a solid? Is it a liquid?
Background:
All forms of matter can exist in three different states: solid, liquid, and gas. Most people know that temperature causes matter to change states. For example, lowering the temperature of liquid water causes it to freeze into solid ice while raising the temperature causes it to boil away into gas as steam. But there are other ways to change the state of matter such as pressure.
Oobleck is a simple combination of corn starch and water but its behavior is anything but simple! Oobleck and other pressure-sensitive substances (like quicksand or Silly Putty) are not traditional fluids but belong to a group called non-Newtonian fluids. Traditional Newtonian fluids (like water or oil) have a constant viscosity or flow regardless of the stress. Hit water with your hand and it splashes everywhere, right? That’s how Newtonian fluids behave. Non-Newtonian fluids such as oobleck, change their viscosity or flow under stress. When you apply a hard, quick pressure to oobleck, it doesn’t splash like water would. Instead, the corn starch particles are forced together so it feels like a solid. But when you slowly move your fingers through it, the particles have time to move apart and it behaves like a liquid.
Are you ready to get a little messy and explore the gooey world of oobleck and non-Newtonian fluids?
Materials:
- 1 cup corn starch
- 1/2 cup water
- Bowl
- Food coloring (optional)
- Oobleck Experiment Test Sheet
Methods:
- Download and print the Oobleck Experiment Test Sheet.
- Pour 1 cup of corn starch into your bowl.
- If using, add a few drops of food coloring to 1/2 cup of water.
- Slowly pour the water into the bowl and stir.
- Once mixed, its time to experiment!
Observations:
- Slowly push your fingers into the oobleck. What do you observe? Does it act like a liquid or a solid?
- Push down hard and fast on the surface. Does it behave differently?
- Grab a handful and squeeze it then let it go. See if you can observe the change from solid to liquid based on the pressure you apply.
- How does this non-Newtonian fluid behave differently than traditional fluids?
A note for parents:
As you can imagine, this experiment can get a bit messy! We at STEM Like a Girl often cringe when our kids ask to do messy projects too. “But I just vacuumed the floors and wiped down the counters!” We get it! Saying yes to the mess will help your daughter have fun while learning about science. And seeing you say yes and embracing her curiosity, mess and all, will build her confidence and encourage her to ask to do other experiments in the future. Oobleck actually wipes off counters very easily with a dry paper towel. To minimize the mess, put a baking sheet under your bowl of oobleck. So go dive into a gooey bowl of oobleck with your daughter – you just might find it fun yourself!
