Food Coloring Fireworks
Fill a large glass with cold water, leaving a few inches at the top. Fill a smaller glass with about 1 1/2 inches of cooking oil. Use an eyedropper to put a few drops of different food colorings into the glass of oil. Stir the oil a little to slightly break up the balls of color. Carefully pour the oil into the glass of water and watch what happens. The oil should rise to the top of the water and slowly release the food coloring into the water, where it will form intricate designs of streaming color that resemble fireworks in the night sky. Record your observations.
Other Things to Try
Repeat the experiment above but use very warm water instead of cold water. Record your observations and compare them to the results from the cold water experiment.
Drop food coloring directly into a glass of water and note what happens.
Fill a glass with water and slowly pour in oil until it forms a thick layer over the top of the water. Gently add a few drops of food coloring. The food coloring should hang suspended above the water in tiny balls. Break one of the bubbles by poking it with a pencil. Observe what happens.
Repeat the experiment with other liquids such as vinegar instead of food coloring and observe the results.
Reconcile Oil and Water
Fill a transparent bottle about halfway full of water. Add food coloring to color the water. Pour oil into the bottle, put the lid on and shake the liquid vigorously. Observe what happens. Do the oil and water mix?
Repeat the experiment but add a dishwashing soap. Do the oil and water mix now? What might this tell us about how soap helps make things cleaner?
Why It Works
Food coloring mixes easily with water, but oil does not mix well with water or food coloring. When oil and water are combined, the oil floats to the surface because it is lighter than water. When you add food coloring to a glass already covered in a layer of oil, the oil won't let the food coloring get through to the water and causes it to float in small globes. When you poke one of the drops, the food coloring escapes to the water with which it mixes. Dish soap is attracted to both water and oil and helps the two substances mix.