What happens when you mix cornstarch and water?


When you mix cornstarch and water, you create a fascinating substance with unique properties. This mixture, commonly known as oobleck, is a non-Newtonian fluid which means it doesn’t behave like a typical liquid or solid. Instead, it exhibits both liquid-like and solid-like properties depending on the force applied to it. Let’s explore the science behind this intriguing concoction.

1. Understanding Cornstarch

Cornstarch, also known as cornflour, is a fine white powder extracted from the endosperm of corn kernels. It primarily consists of starch, a complex carbohydrate made up of long chains of glucose molecules. Cornstarch is commonly used as a thickening agent in cooking and baking due to its ability to absorb and hold water.

2. The Role of Water

Water is a vital component when mixing with cornstarch. It acts as a medium for the starch particles to suspend and interact with each other. Without water, the cornstarch particles would remain separate and not form the unique substance we’re interested in.

3. Non-Newtonian Fluids

Non-Newtonian fluids, like oobleck, do not follow Newton’s laws of viscosity. Instead, their viscosity (resistance to flow) changes based on the amount of force applied. Oobleck specifically falls into the category of shear thickening fluids, meaning its viscosity increases when stress or pressure is applied.

3.1. Shear Thickening

When a force is applied to oobleck by stirring, squeezing, or punching it, the cornstarch particles align and interlock, forming a temporary solid-like structure. This alignment increases the viscosity of the mixture, making it harder to stir or move quickly.

3.2. Shear Thinning

Conversely, when oobleck is left undisturbed or gently poured, the cornstarch particles have time to settle and slide past each other without significant resistance. This allows the mixture to flow and behave like a liquid, with lower viscosity.

4. Oobleck’s Unique Properties

Oobleck exhibits several interesting properties that make it a fascinating substance to experiment with:

4.1. Solidification under Pressure

When a significant force is applied to oobleck, such as squeezing it in your hand, it solidifies and becomes rigid. This phenomenon is known as dilatancy and is a result of increased particle interactions under pressure.

4.2. Liquid Behavior under Gentle Force

When oobleck is poured or gently stirred, it behaves like a liquid, flowing smoothly and easily conforming to its container. This property allows it to be poured like a liquid, despite its ability to solidify under pressure.

4.3. Non-Stickiness

Oobleck has a unique non-sticky texture, making it easy to wash off hands or surfaces. This property is due to the lack of adhesive forces between the cornstarch particles.

5. Applications and Fun Experiments

Oobleck’s fascinating properties have led to various applications and fun experiments. Some notable examples include:

5.1. Body Armor and Protective Gear

Researchers have explored using non-Newtonian fluids, including oobleck-like mixtures, in body armor and protective gear. The ability of these fluids to harden upon impact could potentially provide enhanced protection against blunt force trauma.

5.2. Science Demonstrations

Oobleck is a popular substance for science demonstrations and hands-on learning activities. Its unique properties can be used to explain concepts like viscosity, Newtonian vs. non-Newtonian fluids, and the behavior of matter under different forces.

5.3. Sensory Play and Stress Relief

Oobleck’s intriguing texture and responsiveness make it an excellent material for sensory play and stress relief. It can be used in sensory bins, as a stress ball alternative, or for therapeutic purposes.

6. Precautions and Cleanup

While experimenting with oobleck can be fun, it’s important to consider a few precautions:

6.1. Containment

When mixing cornstarch and water, it’s essential to contain the mixture in a suitable container to prevent spills and messes. A shallow tray or bowl works well for small-scale experiments, while larger containers may be needed for more significant demonstrations.

6.2. Environmental Impact

It’s crucial to dispose of oobleck responsibly to avoid environmental harm. Since it contains cornstarch, which is biodegradable, you can safely dispose of it down the drain, ensuring it doesn’t clog your plumbing.

6.3. Cleanup

After playing or experimenting with oobleck, you can easily clean up any spills or residue using warm water. The mixture will dissolve and wash away without leaving a sticky residue.

7. Conclusion

Mixing cornstarch and water creates a mesmerizing substance with intriguing properties. Oobleck’s ability to transition between liquid and solid states based on applied force makes it a favorite material for scientific exploration, educational demonstrations, and sensory play. Understanding the science behind oobleck allows us to appreciate its uniqueness and potential applications in various fields.

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