Time: 10 minutes.
Materials:mixing bowl, spoon, corn starch, water, food coloring (optional)
- In a mixing bowl, mix 1/2 cup water with 2-3 drops of food coloring.
- Add about 1 cup cornstarch; keep adding by 1 tablespoon increments until the mixture appears firm or is hard to stir.
- Slosh the oobleck around in the bowl. Does it flow like a liquid? What happens when you try to run your hands through it? Or try to pick up a fist-full and squeeze? Now try cutting it with a knife. What happens? Run you finger through the oobleck, both quickly and slowly. Try to stir in some food coloring. What happens? Why is it so hard to stir?
What’s happening: This concoction is an example of a “Non-Newtonian” fluid – meaning, it mostly acts like a liquid, but sometimes acts more like a solid. When you press on the oobleck by stirring it or running your finger through it, the molecules compress and make the oobleck feel like a solid. This is how quicksand works!
Time: 5 minutes.
Materials: shallow container, toothpick or pencil, milk, food coloring, liquid soap
- Pour enough milk into a shallow container to cover the bottom to a depth of about ½ inch. (The greater the surface area, the cooler this experiment is, so choose a wide container.)
- Place dots of food coloring in different spots on the surface of the milk, about the size of a dime, making sure the spots aren’t touching. (Use different colors for different spots.)
- Place a glob of liquid soap on the tip of the toothpick or pencil. Say 1-2-3, then plunge the glob of soap into the center of each of the colored dots. The colors will go flying through the milk!
What’s happening: The soap is breaking up the surface tension of the milk. The milk molecules usually cling to each other, but wherever the soap touches them, it makes them spread apart. The food coloring helps you see the movement of the milk molecules in reaction to the soap.
Time: 5 minutes
Materials: small glass, baking soda, vinegar or lemon juice, food coloring (optional)
- Mix ½ cup vinegar or lemon juice with food coloring.
- Put a tablespoon of baking soda in the bottom of a glass.
- Move the glass over a sink, and pour in the liquid. Watch out – the glass will erupt like a volcano!
- A fun variation: put the vinegar or lemon juice in an empty plastic water bottle. Scoop the baking soda into a balloon. Carefully attach the balloon to the top of the bottle without spilling its contents. Once it’s attached, tip the balloon up and dump in the baking soda. The balloon will blow itself up!
What’s happening: A chemical reaction is occurring between the acid (vinegar or baking soda) and base (baking soda). This reaction forms a gas (carbon dioxide – the same stuff we humans breath out!), which is what causes all the bubbling, and causes the balloon to inflate.