BACKGROUND

Here’s a twist on this classic classroom experiment/demo: By adding glow-in-the-dark paint and an ultraviolet light source, we can start a classroom discussion on the states of matter, non-Newtonian fluids and we can introduce fluorescence, because who doesn’t love glow in the dark stuff!

This project encourages students give into their natural curiosity, to play, to ask questions, and with the proper guidance, to make observations that will answer their questions. And bonus points, they get to make a little mess. Don’t worry, clean-up is easy.

THE BASICS

Oobleck is named after the green sticky goo in Dr. Seuss’ “Bartholomew and the Oobleck.” Oobleck is a Non-Newtonian fluid.

Non-Newtonian fluids change viscosity when a sheer force is applied. Some materials increase in viscosity, like Oobleck. While others, like ketchup become less viscous when a sheer force is applied. Their behavior is reliant on the strain rate or how quickly you move through or around them.

Examples: Oobeleck blood, ketchup, mayonnaise, quick sand.

Newtonian Fluids have constant viscosity, regardless of the forces acting on it.

Examples: Water, alcohol.

Fluorescence occurs when light is given off by a substance after it absorbs (usually) higher energy light/shorter wavelength of light or electromagnetic radiation.

Fluorescence is used in chemistry, geology, biology and chemical sensors

W A R N I N G

UV light can cause macular degeneration, cataracts and cancer

Always wear the appropriate safety glasses when working with UV lights.

UV safety glasses are easy to find, are inexpensive and can be used as everyday safety glasses.

If the glasses are too large for small children, use a UV face shield.

Look for safety glasses listed as Ultraviolet Radiation Blocking Spectacles/Glasses/Googles/shield

Supplies

Corstatch
Water
Bowl
Measuring Cups
Glow in the Dark Paint
Spatula/large spoon
Blacklight/ UV light
UV Safety Glasses

Extra Supplies if time and budget permit:

Subwoofer Speaker
Plastic wrap
Mobile device with Frequency Generator App

Step 1: The Cornstarch

Place ½ cup of cornstarch in a mixing cup or bowl
The proportions of water to cornstarch is~ 1:2. One-part water to two-parts cornstarch. Scale up as needed.
Transfer to a mixing cup or bowl.

Step 2: The Water

Measure out ¼ cup water.

Step 3: The Paint

Add a bit of paint to ¼ cup water.
Stir

Step 4: Mix Oobleck

While stirring, slowly add the water to the cornstarch.
- It should be the consistency of thick pancake batter.
- If the Oobleck it is powdery, add more water.
- If it splashes add more cornstarch.

Step 5: Play

This is a hands-on experience:

Stick your hands in it.
Try to scoop it up.
Slowly move your fingers through it.
Move your fingers through it quickly and note the difference in behavior.
Squeeze it into a ball and see what happens when you let go.
Just play with it for a few minutes.

Step 6: UV Light Demo

Dim the room lights.
Put on UV safety glasses.
Shine UV light on the Oobleck.
Shine the light on other objects to illustrate that not everything is fluorescent.
Introduce the idea that the kind of particles (atoms and molecules) that make up matter have different properties. Let them know that you will continue a discussion on glow in the dark matter in a later lesson.

NOTE:

Let me know what questions you want answered and I will try to include them in a UV light lesson Instructable.

Step 7: Dancing Monster Demo

Time (and budget) permitting:

Remove the cover cloth from the subwoofer's speaker cone.
- Cover the speaker cone with a piece of plastic wrap or plastic bag.
- Set the volume to the lowest setting (speaker).
Add some Oobleck on top of the speaker cone.
- Allow it to puddle.
- Once it fully puddles, ask students to describe the Oobleck.
Plug the Speaker to your mobile device.
- Set the volume to the lowest setting (on mobile device).
Set the Frequency generator to 30 Hz.
Very slowly increase the volume on both speaker and mobile.
- As you increase the volume, watch students for any sign of discomfort from the noise. These frequency might disturb children with sound sensitivity.
- Stop or lower the volume if necessary.
Once you find a comfortable volume for the students, change the frequency.
- Change the frequency in small steps.
- Go up to ~60 Hz.
Ask students to observe and describe the Oobleck's reaction.
Encourage students to play with the dancing Oobleck.
Introduce the idea of sound as a force. This force is acting on the Oobleck making it move around. If students resist the concept of sound as a force, ask them to place their hands on the speaker so than can feel as well as hear sound.

Step 8: Discussion Points

What is Matter?
- Matter is anything that takes up space and has mass. Matter is the stuff stuff is made of.
- Matter can come in different forms. Let’s keep it to solids, liquids and gases for this discussion.
Liquid, Solid or Gas?
- Solids keep their shape. They have tightly packed particles (comparatively). The particles are bound together.
- Liquids take the shape of their container. Liquids have particles that are loosely bound together. Particles can move around in a liquid, but not as much as in gases. Liquids keep their volume.
- Gases fill their container. Particles in gases can move freely and quickly so gases do not have a definite shape or volume.
  - if students have difficulty understanding what a gas is, discuss bubbles in soda, air in a balloon or soap bubble. Some students will not understand that gases have mass, discuss their experiences with air filled balloons vs helium filled balloons and why one floats.

Have students make basic observations. If they are stuck here are some questions they can investigate: