Science experiments are my favorite activity to do with my kids, especially when you already have the supplies on hand. This is one of my favorites:
What you'll need:
2 percent milk or half & half (do not use nonfat milk)
Food coloring (at least two colors)
Clear dish soap
Fill a white bowl with milk or half & half. If you don't have a white bowl, make sure you pour enough milk into the bowl so you can't see the bottom. Add a few drops of food coloring. Now add a drop of dish soap and watch what happens!
Make sure you use at least 2% milk or half & half since the fat in the milk helps to cause the reaction. The milk's fat and protein are very sensitive to chemical changes. The chemicals in the soap cause the chemical bonds that hold the protein together in the milk to weaken. The dish soap also reacts with the fat in the milk, which is why we see these colorful swirls.