When Liquids Meet (Grades K-2)

Find out what happens when two different liquids meet in this simple hands-on science experiment. 

Colored Liquids swirl together

What You Need

  • Four clear 8-ounce cups or 16-ounce deli containers
  • Water
  • Food coloring (red, green and blue work best) 
  • Cooking oil
  • Milk
  • Plate (or another flat-bottomed container)
  • Toothpick or cotton swab
  • Liquid dish soap

What To Do


Add the same amount of water to each container. Put one drop of food coloring in the first container and observe what happens. Now try a different color in each cup. What do you notice? 

The food coloring normally begins to drop through the water and starts to dissolve. Since food coloring is mostly made of water and dye, the food coloring will eventually disperse, or spread through the water. 

Try this: What happens if you try the same experiment with warm water? 


Rinse out the containers used for the previous experiment. Fill each container about ¾ full with oil. Put one drop of food coloring in the water and observe what happens. 

Try adding another color to the same cup. Observe what happens. What questions do you have? 

Water and oil do not mix because they have different densities. The food coloring will stay in a rounded ball, and bob up and down in the oil. 

What happens if you cover and gently shake the container, or if you stir it? Now wait five minutes, and observe again. What do you notice? 

Food coloring drops going into water


Pour just enough milk to cover the bottom of a plate or another flat-bottomed container, like a pie plate or cake pan. Add four drops of food coloring and observe. 

Coat the end of a cotton swab or toothpick with a drop of dish soap. Touch the toothpick to the surface of the milk, and observe the reaction. 

You can try different dairy products (whole milk, cream, skim milk) to see if you notice any differences. 

Milk has fat in it, which behaves like an oil with water. Water and fats do not mix, but when you add a drop of soap, the fat bonds in the milk break apart and allow the food coloring to spread and mix.