Cornstarch goop (aka 'Oobleck") is a perfect medium for scientific exploration. There are only two ingredients – cornstarch and water. As the children mix it together, its properties and texture change, providing opportunities to observe and figure out what has happened, and what might happen next.
I set up the activity on individual trays, so each child can have control over their own exploration process from beginning to end. There’s no exact “recipe”, but I start with giving each child an equal amount of water and cornstarch. They can decide if they need more.
Adding color extends the activity by giving more dimensions to observe and interact with. The color also makes it easier to see the physical changes in the mixture, since the color mixes with the more liquid part of the mixture, floating above the solid goop. I used liquid watercolor, which doesn’t stain the way food coloring can.
The goop is also a medium for studying color mixtures. Diffused through the thin cornstarch mixture, the colors swirl and combine slowly, allowing the children to control the combinations, and observe the effects of their actions.