How to oobleck

What is Oobleck?

Oobleck is a fascinating substance that behaves like both a solid and a liquid, depending on how you interact with it. It's scientifically classified as a non-Newtonian fluid, specifically a shear-thickening fluid. This means that under pressure or sudden force (like punching or squeezing), it becomes more viscous and acts like a solid. However, when the pressure is released or the force is gentle (like letting it drip or slowly moving your hand through it), it flows like a liquid. This unique property makes it a popular choice for science experiments, sensory play, and educational demonstrations.

How to Make Oobleck

Making oobleck is incredibly simple and requires only two common household ingredients: cornstarch and water. The process is straightforward and can be done in minutes, making it an ideal activity for kids and adults alike.

Ingredients:

• Cornstarch (also known as cornflour in some regions)
• Water
• Optional: Food coloring (for visual appeal)

Equipment:

• A large bowl or container
• A spoon or your hands for mixing

Instructions:

1. Start with Cornstarch: Pour a quantity of cornstarch into your bowl. A good starting point is about 1 cup (approximately 120 grams) for a small batch.
2. Add Water Gradually: Slowly add water to the cornstarch. For every 2 cups of cornstarch, start with about 1 cup of water. It's crucial to add the water gradually, mixing as you go.
3. Mix Thoroughly: Use a spoon or your hands to mix the cornstarch and water. You're aiming for a consistency where the mixture feels solid when you squeeze it quickly but becomes liquid when you relax your grip. If it's too watery, add more cornstarch. If it's too stiff and crumbly, add a tiny bit more water. The ideal ratio is often around 2 parts cornstarch to 1 part water, but this can vary slightly depending on humidity and the specific type of cornstarch.
4. Add Color (Optional): If you want colored oobleck, add a few drops of food coloring to the water before mixing it with the cornstarch, or mix it in after the initial oobleck base is formed. Be aware that food coloring can stain, so consider wearing old clothes or an apron.
5. Test the Consistency: Once mixed, test your oobleck. Try to punch it quickly – it should feel hard. Then, slowly dip your fingers into it – it should flow around them.

Tips for Playing with Oobleck

Playing with oobleck is a sensory experience that encourages exploration and understanding of its unique properties. Here are some tips to enhance the fun and learning:

• Sensory Exploration: Encourage children to explore the texture with their hands. They can try scooping it, letting it drip through their fingers, or squeezing it into a solid ball and watching it melt back into a liquid.
• Tools for Play: Use various tools like spoons, cups, funnels, and cookie cutters. Observe how the oobleck behaves when poured through a funnel or when trying to cut shapes with cookie cutters.
• Containment is Key: Oobleck can be messy! Play with it in a designated area, such as a large plastic bin, a tray, or outdoors. Cover surfaces with a tablecloth or newspaper.
• Cleaning Up: Oobleck is easy to clean up. Once the play session is over, let the oobleck dry out. It will turn back into powder and can be swept or vacuumed up. Do not pour large amounts down the drain, as it can clog pipes. Instead, scrape excess into the trash or let it dry and dispose of the solid mass.
• Experimentation: Encourage further experimentation. What happens if you try to run across a large batch? (It's difficult!) What happens if you put small toys in it? How does it feel when it's warm versus cool?

The Science Behind Oobleck

Oobleck's behavior is a classic example of non-Newtonian fluid dynamics. Unlike Newtonian fluids (like water or oil), whose viscosity remains constant regardless of the applied stress, non-Newtonian fluids change their viscosity based on the stress applied. Oobleck is a type of non-Newtonian fluid called a shear-thickening fluid (or dilatant). The cornstarch particles in the mixture are suspended in water. When you apply sudden pressure, the cornstarch particles jam together, creating a temporary solid structure that resists the force. When the pressure is removed, the particles disperse again, and the mixture flows like a liquid. This phenomenon is due to the way the cornstarch granules interact with the water molecules under different forces.

History and Popularity

The substance known as oobleck gained widespread recognition through its inclusion in science museums, most notably as part of the "Newton's Laws of Motion" exhibit at The Franklin Institute in Philadelphia. It was named after the Dr. Seuss book "Bartholomew and the Oobleck," where a similar sticky green substance falls from the sky. Its simple composition, engaging properties, and educational value have cemented its place as a staple in early childhood education and home science exploration.