Simple Science December 3, 2001
Educational Goo
Simple experiments that demonstrate scientific principles have been around for a long time. You can often find all the materials you need for excellent experiments in your own home. Some classic experiments revolve around creating gooey substances. Playing with slime is fun — and surprisingly, you can learn a lot from it, too.

To make your own slime, follow these instructions:

    (1) Pour a cup of cornstarch into a bowl.

    (2) Slowly add 1/2 cup of water, just a little at a time, mixing with your fingers as you go. To give your mixture real slime appeal, add a few drops of food coloring.

Now, pick up the ooze in your hand and squeeze it. What happens? Record your observations below.

Action What happens?
Squeeze the ooze.

 
Shape it into a ball.

 
After shaping the ooze into a ball, open your hand.

 
Gently bang on it with a spoon.

 
Place a tiny object like a paper clip on top of it.

 
As you pour ooze into another container, try and cut it with a pair of scissors.

 

You have just made what is known as a "non-Newtonian" fluid. In the 1700s, Sir Isaac Newton described the properties of ideal fluids. He said an ideal fluid would have a constant viscosity, or resistance to flow, at a given temperature. Your experiments proved that your ooze is a non-Newtonian fluid because it has the properties of both a liquid and a solid and reacts to stress with increased viscosity.

Quicksand is another non-Newtonian fluid. That means the more you struggle against it — or try to "cut" through it — the more resistant it gets, which explains why you shouldn't struggle violently if you happen to fall into it! (While we're on the subject, the best thing to do if you fall into quicksand is to swim out slowly.)

  • What are some other non-Newtonian fluids you use in everyday life? Hint: You might find some of them in a restaurant and others in an art class. (See the sidebar on the right for examples.)

What is Rheology?
"Rheology" is the study of the change in form and flow of materials. For example, rheology would be concerned with how water behaves when you stir it or pour it. Does it get thicker or thinner? The answer is that water's viscosity does not change when a stress is placed on it. It's a Newtonian fluid. Another Newtonian fluid is gasoline.

Non-Newtonian fluids can be found in nature and created artificially. The viscosity of these fluids does change when they are put under stress. Natural examples are tree sap, saliva, and even DNA. Artificial examples are tomato ketchup, glue, and toothpaste.

The Massachusetts Institute of Technology has some interesting videos of other non-Newtonian fluids in action. Some of the language used in this site is very advanced (it's for university-level students), but the videos are excellent.

Dancing Raisins
Here's another quick and easy science experiment. All you need is a glass of clear soda, such as ginger ale or club soda, and several small raisins.

    (1) Fill a glass with soda. Leave about 1/2 inch (12.5 mm) of space at the top.

    (2) Drop the raisins in.

What happens?

Those tiny bubbles attaching themselves to the raisins are carbon dioxide (CO2) bubbles. The irregular surface of the raisins enables a lot of CO2 to accumulate. When enough gas bubbles attach to the raisins, they act like tiny balloons, giving the fruit enough lift or buoyancy to rise.

The raisins should rise to the top of the glass and float on the surface. As the carbon dioxide escapes into the atmosphere, though, the raisins will sink. Then the whole process will repeat itself time after time — so the raisins seem to dance.

What other small objects might work in this experiment? Try out a variety of objects, and see if you can tell what properties the objects need to share for this experiment to work.

Carbon dioxide gives soda its fizz. Alka-Seltzer medicine uses fizzing bubbles to make people feel better fast. How does this work? The bubbles tickle the exit valve of the stomach, making it open sooner than normal, which allows the medicine to get into your system more quickly.

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More Links
Try the Bizarre Stuff You Can Make in Your Kitchen Web site.

Visit BillNye.com to find experiments to try at home. Just look for "Home Demos" when you've entered the site.

Younger students can explore many science concepts with these fun and easy-to-do experiments.

Visit the Web site of Brien Engel (pictured below), a professional "glass harpist". Brien has a good explanation of the science of glass harps. Another glass harpist, Dillinger Lee Heermann, features recordings of glass music on his Web site.

The Sound of Music
Did you know that the musical scale is built upon a mathematical relationship? This experiment helps you understand how a math connection leads from one note to the next. You will need eight identical drinking glasses, some water, a ruler, and a metal spoon. You're going to make a simple version of the instrument known as the "glass harp."
    (1) Line the eight glasses up side by side.

    (2) Completely fill the first glass with water. This represents your low C note.

    (3) Pour water into the next glass until it is 8/9 full. (Use a ruler to fill this glass and the others.) This second glass is your D note.

    (4) Fill 4/5 of the next glass. This is your E note.

    (5) Fill 3/4 of the next glass. This is your F note.

    (6) Fill 2/3 of the next glass. This is your G note.

    (7) Fill 3/5 of the next glass. This is your A note.

    (8) Fill 8/15 of the next glass. This is your B note.

    (9) Fill a glass half full. This is your high C note.

As you go about this project, occasionally tap the sides of the glasses gently with a spoon to make sure you are hearing differences in pitch.

  • What happens to pitch when you add water?

What is the science in this experiment? Sounds are made by vibrating objects. The number of times an object vibrates in a set period of time is called the frequency of sound. As the frequency increases, the pitch of the sound gets higher. When the glass is struck by the spoon, both the water and glass begin to vibrate. This back-and-forth motion transfers to the air in the glass. These air vibrations come to us as sound. As you add water, the amount of vibrating material increases, slowing down the vibrations. Since there is more material to vibrate, a lower pitch is produced.

Shorter String, Higher Pitch
The scientific principle used to create the musical notes with glasses of water is the very same one that is used in many musical instruments, such as the guitar, violin, and piano.

These instruments play sounds of different pitches using strings of different lengths. The shorter the string, the higher the pitch. When you're playing the guitar, you place your finger higher on the fretboard. By placing your finger on a string high on the fretboard, you are basically shortening the length of the string, and so the string vibrates at a higher frequency — giving you a higher-pitched sound.

Let's see if you can apply the mathematical connections of sound to a real-life situation.

  • If a 20-inch organ pipe produces a C note, what note would a pipe 3/4 of this length produce?
  • How many inches long would the organ pipe be that produced an A note?
You're the Scientist
There are many other experiments that you can try at home or in your classroom. Whether you want to crumple a metal can simply using the atmosphere or build your own mini-rocket, you can get hands-on experience of fundamental scientific principles. You can get guidelines on conducting these experiments from the Web sites listed above and to the right. Have fun — and remember to be careful, too!

Related Activities
Properties of Gases
You can learn more about gases in this Middle School Gateways activity.
Making Music
Have fun making your own musical tunes with this Tangible Math activity.
What is a Wave?
Explore the science of sound waves further with Middle School Gateways activities.
Music & Technology
See how sounds are created and combined in this Riverdeep archive article.