This post was inspired by an experiment in the back of the book Flash Facts, a STEAM Graphic Novel I shared in a post last week. The book is a series of short STEM inspired stories featuring DC Superheroes, and there are eight fun experiments in the back of the book. This experiment was one of our favorites, and I’ve used their basic idea and added on to make it our own for this post.

In this experiment kids can see water molecules moving around by using food coloring. They also discover that molecules move faster in hot water than cold water. You and your kids will love this super simple, super fun, and super educational STEAM Activity that’s inspired by a super book ;)!


  • 3 clear cups or glasses
  • Hot water
  • Warm water
  • Ice water
  • Food coloring (I recommend a darker color like green, blue or red, so it’s easier to see in the water)


  1. Fill one cup with ice water. You can start with ice cubes in the water to make it extra cold, but remove the ice cubes with a spoon before adding the food coloring.
  1. Fill one cup with warm/room temperature water.
  1. Fill one cup with very hot water (I used the hottest water from my kitchen sink) – parents do this step so kids don’t get burned.
  1. Line up the 3 cups in a row in front of your child.
From left to right: cold water, warm water, and hot water. We removed the ice cubes from the cold water right before adding the food coloring. My kids chose to use green food coloring.
  1. Put one drop of food coloring in each cup (try to do this quickly, one after the other, starting with the ice water and ending with hot water so you can see all affects at once). Do not move the cups or stir the water in any way.
  1. Observe what happens to the food coloring, and how it moves through the water in each cup.
Hot water
(1 minute after adding food coloring)
Warm water
(1 minute after adding food coloring)
Cold water
(1 minute after adding food coloring)
Immediately after adding food coloring
2 minutes after adding food coloring

STEAM Concepts Learned:

  • Science: Your kids are seeing the magic of molecules in action! Water is made up of many H2O molecules that are moving around in each cup. When you heat up the water molecules they move faster. When you add the food coloring, you are seeing the molecules move through the color and move it around the cup. The coloring spreads quickest in the hot water because those molecules are moving the fastest, and the coloring spreads the slowest in the cold water because those molecules are moving slower by comparison.
My kids liked putting their hands on the cups to feel the hot, warm and cold water while watching the food coloring move around in the cups.

My kids really loved this simple science experiment. It was so quick to set up and see the reaction, and you probably have everything you need at home right now. I hope you try this fun activity with your kids and let me know how it goes!


Some of the links below are affiliate links, which means that if you click on a product link I may receive compensation at no additional cost to you. I only link to products and pages I personally use and highly recommend. As an Amazon Associate I earn from qualifying purchases. Thank you for your support!

You have Successfully Subscribed!