Why does cornstarch and water make Oobleck?

When cornstarch and water are mixed together, they form a non-Newtonian fluid known as Oobleck. This fluid exhibits properties of both solids and liquids, depending on the force applied to it.

Cornstarch consists of tiny starch granules that are densely packed. When water is added, these granules absorb the water and become hydrated, forming a loose network of particles that can slide past each other. This gives Oobleck its liquid-like properties.

However, when a force is applied to Oobleck, such as when you poke or squeeze it, the starch granules come closer together and form a more rigid structure. This structure traps the water molecules and prevents them from flowing freely, giving Oobleck its solid-like properties.

As soon as the force is removed, the starch granules disperse again and Ooblek reverts back to its liquid state. This unique behavior of Oobleck is due to its shear-thickening properties, where the fluid becomes more viscous when subjected to shear forces.

The ratio of cornstarch to water determines the consistency of Oobleck. A higher proportion of cornstarch will result in a thicker and more solid-like Ooblek, while more water will make it thinner and more liquid-like.

Oobleck is a fun and educational material that can be used to demonstrate the principles of non-Newtonian fluids and shear thickening. It's also a great sensory activity for kids, as it can be molded, squeezed, and played with in various ways.