What You Did
You made what is commonly known as “oobleck”, which mimics the properties of both liquids and solids, depending on how much pressure you exert upon it.
Intended Results
Your mixture should act like a liquid: it will run through your fingers and pour or drip into a bowl and you can submerge your hand in it. Your mixture should act like a solid: push on it firmly with your fingers or quickly smack it with the back of a spoon.
Unintended Results
My original experiment called for a ratio of 2:1 cornstarch and water, but it was too dry, so if you use too little water, your mixture will act like a solid.Evaporation will happen as you play with your oobleck, so you may need to add a small amount of water if you play with it for awhile.If you use too much water, it will act more like a liquid until some water evaporates away. Keep playing with it, and it will behave!
Keep Tinkering
Add food coloring. Vary the proportions of cornstarch and water. Store it in a zippered sandwich bag
Explored Concepts
states of matter, viscosity, non-Newtonian fluids, water cycle, evaporation