Oobleck presents a fascinating puzzle, often baffling those who encounter it for the first time. This mysterious substance challenges our everyday understanding of how matter behaves, leaving many to wonder if it is a solid, a liquid, or something entirely different. Its intriguing nature sparks curiosity about the fundamental properties that define states of matter.
Understanding Traditional States of Matter
To appreciate oobleck’s unique characteristics, it helps to first consider the traditional states of matter.
Solids possess a definite shape and a definite volume, maintaining their form unless acted upon by an external force. Their particles are closely packed and vibrate in fixed positions.
Liquids, conversely, have a definite volume but take the shape of their container, allowing them to flow freely. The particles in a liquid are close together but can move past one another.
Gases lack both a definite shape and a definite volume, expanding to fill any container they occupy. Their particles are widely spaced and move randomly.
Oobleck’s Peculiar Behavior
Oobleck demonstrates a remarkable duality, exhibiting properties of both liquids and solids depending on the applied force. When left undisturbed, it behaves much like a liquid; one can slowly pour it from one container to another, and it will conform to the shape of its vessel. A finger gently dipped into oobleck will sink slowly, just as it would in water. However, applying sudden pressure transforms its demeanor entirely. A swift punch to the surface will cause it to feel solid and unyielding, resisting the impact. It is even possible to roll a ball of oobleck in your hands, but if you stop applying pressure, it will quickly melt back into a liquid state. This rapid change in consistency is what makes oobleck so captivating.
The Scientific Classification: Non-Newtonian Fluids
Oobleck is neither a true solid nor a true liquid; instead, it is classified as a non-Newtonian fluid. Unlike Newtonian fluids, such as water, whose viscosity remains constant regardless of the applied stress, the viscosity of a non-Newtonian fluid changes under different shear stresses. Oobleck specifically falls into the category of a shear-thickening fluid, meaning its resistance to flow, or viscosity, increases when a shearing force is applied.
This phenomenon occurs because oobleck is a suspension, a mixture where solid particles are dispersed in a liquid. In the case of oobleck, fine cornstarch particles are suspended in water. When a sudden force is applied, the water is squeezed out from between the cornstarch particles, causing them to jam together and form temporary, rigid structures. This temporary particle interlocking gives the mixture its solid-like resistance until the force is removed, allowing the water to flow back in and the particles to separate, returning it to a liquid-like state. This explains why it resists rapid movements but flows easily when handled gently.
Making Oobleck and Seeing it in Action
To create your own, simply mix two parts cornstarch with one part water in a bowl. Start by adding the water slowly to the cornstarch, stirring until you achieve a consistency that is thick but still pourable. You can then experiment with its fascinating behavior.