I saw a video of a science experiment I thought I'd share. This is a simple activity requiring few resources (milk, plates, food coloring, soap and cotton swabs) that you can perform with your students.
If you place a bit of milk in a plate with a few drops of food coloring in different hues, adding a bit of soap ignites a spectacle of swirls and spinning colors. Kids would love to see the colors mixing together in a really surprising visual effect. Explain the science behind it (involving the molecules in the soap "chasing" the molecules in the milk). The video below explains the concept and shows you how the colors look once the soap is introduced. You can also turn it into an experiment for students to record how the colors react in different types of milk and other liquids. I've included a printable sheet for students to record their data during the activity.