What Kind of Liquid Can Sometimes Act Like a Solid?
One of the first things young science students learn is the difference between solids, liquids, and gases. Though the differences between the three main states of matter seem to be clearly defined, there are some materials that require a closer look. A special kind of liquid, called a non-Newtonian fluid, is an excellent example of this. In this activity, elementary students will perform a hands-on experiment that will help them learn about these amazing substances that can sometimes act like a liquid and sometimes act like a solid. Many teachers and students know this non-Newtonian Fluid as Oobleck. Now just think how much better it will be when you teach about it because you will know the science behind it all!! You don’t have to save it for Dr. Seuss’ birthday. It’s too good to only use once a year.
Learning about the properties of matter provides an excellent opportunity for students to gain valuable hands-on experience in performing scientific experiments. In this experiment, students will first create a non-Newtonian fluid using items commonly found around the house. They will then test the properties of the fluid they created to determine what kinds of interactions cause the mixture to act like a liquid or a solid.
What You’ll Need
- 1/4 cup corn starch
- 1/4 cup water
- a mixing bowl
- measuring cup or spoons
- newspaper or paper towel
How To Make a Non-Newtonian Fluid
- Cover your work area with newspaper or paper towel for easier cleanup afterward.
- Measure 1/4 cup of corn starch powder, and pour it into the mixing bowl.
- Add 1/8 cup (2 tablespoons) of water to the bowl and stir slowly.
- Continue to add water to the mixture slowly while stirring constantly at a slow pace. It may help to have one partner stir the mixture while the other adds the water.
- Stop adding water when all of the corn starch is mixed with water into a thick, sticky mixture. If it becomes too watery, add more cornstarch.
- Use your hands to scoop up a handful of the mixture. Close your hand around the mixture and form it into a ball. Be sure to keep pressure on the mixture. After forming the mixture into a solid ball in your hand, hold your hand out flat and watch the mixture fall back into a puddle in your palm.
- You can also try pouring the mixture onto the newspaper or paper towel. Slowly and gently move your fingers through the mixture. Then, use a moderate amount of force to tap or slap the mixture. What did you notice?
Can you think of any other tests to perform with the mixture?
What Do You Observe?
Students should be asked to record their observations both when the mixture is left to sit on its own (i.e. in an open palm) and when a force is applied to it (i.e. when pressed into a ball). They should observe that the mixture behaves like a liquid when it is at rest or acted upon slowly and with low force. They should also note that applying force to the mixture—by rubbing it, tapping it, or trying to quickly move their fingers through it—causes it to become solid. Ask the students to hypothesize why the mixture behaves this way. Students should be encouraged to experiment with the mixture to see what kinds of tests they can put it through.
Background: The Science of Non-Newtonian Fluids
All matter is made up of tiny particles called atoms. Millions or even billions of atoms join together to form everything around you. Chairs, pencils, water, and even people are all made up of atoms. The atoms that make up an object are always moving. How fast they move determines whether the object is a solid, liquid, or gas. In a solid, like ice, the atoms are packed tightly together and moving slowly. When heat is applied, the atoms begin to move more quickly, and the ice melts into water. If more heat is applied, the atoms being to move very quickly, covering even larger distances in their movements. This results in the water turning into steam.
For a material is in its liquid state, such as water, the atoms can move around easily enough to allow the material to easily flow, change shape, and even give way when a solid object passes through it. These liquids are called Newtonian fluids because they follow a set of rules for the movement of fluids outlined by scientist Isaac Newton. However, a non-Newtonian fluid behaves differently. These fluids are generally thick and sticky. Their atoms move enough to allow the material to pour and change shape, but only if it is done slowly. If you try to manipulate it too quickly, its atoms ram into each other, forming a solid temporarily.
Aaron gives us the science and a great experiment I found The Slow Mo Guys on You Tube have a great video in what else…..SLO MO. These guys like a bit scrappy..(in a totally cool way) but the kids think they are super cool. Check out the video below.
To better understand this phenomenon, think of the hallways in your school. All of the students in the school are going down the same hallway at the same time. Students from each class are grouped together in lines. Lines going one way down the hall stay to the right, while lines going the other way stay to the left. The students in the school can easily move up and down the hallway in this scenario. This is like the atoms in a Newtonian fluid. Now image all of the students are packed together, filling the width of the hallway. If one student were to walk slowly down the hallway, she would be able to work her way through the crowd and get to the other end of the hall. However, if the student were to run at full speed down the hallway, she would slam into the crowd of kids and come to an abrupt stop. This is how a non-Newtonian fluid works.
Thanks to Aaron Carr for another excellent post. Aaron has a book that has more information on this topic. Properties of Matter at Amazon if you would like to check it out. It has excellent photos and great information! I’m not affiliated with Amazon but Aaron would appreciate it if you have time to check it out.
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If you like the Slo Mo Guys check out more of their videos here!