Skip to Content

Amazing Hot and Cold Water Density Experiment

Save this idea for later!

One of my favorite things to do are STEM activities and ocean science experiments! I love seeing the reaction on a child’s face when they see science work before their eyes.

A lot of science experiments take a long time, but not the hot and cold water density experiment!

In this temperature density experiment, kids will experience water density, color mixing, molecule science, and a whole lot more with just one experiment that takes less than 10 minutes to complete.

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home. #science #stem #stemed #scienceclass #scienceexperiment #elementary #kidsactivities #learningactivities #teachingideas

Try it out at home or in the classroom!

Hot and Cold Water Density Experiment

If you love doing quick science experiments that wow, try this amazing hot and cold water experiment.

Kids will ask to do this one over and over again!

For more density science experiments, try making a sugar rainbow, rainbow density jar, ocean density jar, or a Halloween density jar!

You’ll also want to check out the ultimate list of summer STEM activities and the ultimate list of summer science experiments.  These are super fun ways to add a bit of STEM learning to your summer fun!

Why do a hot and cold water experiment with food coloring

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home.

Today, science experiments for kids are more important than ever. Science and technology are huge parts of our world today, and the future will be even more science and tech-focused.

Kids who aren’t immersed in the world of science and STEM exploration from a young age will be left behind their peers, and may struggle to find work in the fast-changing landscape of future careers.

Science experiments are usually basic, but they can help spark a love of science and discovery in a child that will follow them throughout their life.

The simple science experiment that a child does today may spark their desire to discover something that will change the world in the future.

Every day, young children are using science experiments to solve real-world problems in medicine and technology that have never been uncovered before.

And all these scientific discoveries start with a firm foundation in science and STEM.

Don’t Miss: 31 Creative STEM Activities for Kids

elementary stem challenge cards

THE SCIENTIFIC METHOD FOR KIDS

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home. #science #stem #stemed #scienceclass #scienceexperiment #elementary #kidsactivities #learningactivities #teachingideas

Every science experiment contains four elements:

A Question

Kids should start every science experiment with a question, even if that question is just “what will happen?”

A Hypothesis

Before doing any experiment, children should record what they believe will happen.

An Experiment

This is where the fun part comes into play. Test the hypothesis to determine if it answers the question fully.

A Recording and Analysis

As the test is completed, record what happened and analyze why.

A Re-test

Try different variables and try a new test to see if the original answer is confirmed or disproved.

You may also like: Quick STEM Activities for Kids

hot and cold water experiment

Hot water and cold water experiment explanation

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home. #science #stem #stemed #scienceclass #scienceexperiment #elementary #kidsactivities #learningactivities #teachingideas

Here is the hot and cold water density experiment explanation.

The hot and cold water science experiment works because of the different density of hot and cold water.

Certain liquids are less dense than others. If you’ve ever made a density jar, it’s easy to see this in action.

But… water has the same density as other water, right? So why does it stay separated?

The secret is in the temperature of the water.

The molecules in hot water move faster than those in cold water. Hot water molecules bounce around and leave gaps. This makes hot water slightly less dense than cold water.

So when you put the cold water on the bottom, the denser cold water stays there.

But when you put the cold water on the top, heat molecules rise. So the colors mix right away.

Because you’re mixing primary colors, they mix into secondary colors when the hot water is on the bottom.

elementary stem challenge cards

Hot and Cold Water Science Experiment Kits for Kids

This post contains affiliate links. See my disclosure policy for details.

If you’re in a rush, these are our favorite weather science kits.

SPLASH! Water Science Kit with 23 ExperimentsSPLASH! Water Science Kit with 23 Experiments4M Clean Water Science4M Clean Water ScienceWater: Up, Down, and All Around (Amazing Science)Water: Up, Down, and All Around (Amazing Science)The Emerging Science of Water: Water Science in the XXIst CenturyThe Emerging Science of Water: Water Science in the XXIst CenturyScience4you Water Science Kit ExperimentScience4you Water Science Kit ExperimentWater (Science Emergent Readers)Water (Science Emergent Readers)

What You Need to Do The Hot and Cold Water Density Science Experiment

12 Ball Mason Jar with Lid - Regular Mouth - 16 oz by Jarden12 Ball Mason Jar with Lid – Regular Mouth – 16 oz by JardenSpice Supreme Assorted Food Colors Red Blue Green Yellow 1.2 OzSpice Supreme Assorted Food Colors Red Blue Green Yellow 1.2 OzAmazonBasics Thermal LaminatorAmazonBasics Thermal LaminatorNeenah Creative Collection Classics Specialty Cardstock Starter Kit, 8.5 X 11 Inches, 72 Count (46407-01)Neenah Creative Collection Classics Specialty Cardstock Starter Kit, 8.5 X 11 Inches, 72 Count (46407-01)

Hot and Cold Water Experiment with Food Coloring

Mixing Hot and Cold Water Experiment Set Up

Before starting this experiment, you’ll need to laminate a small card slightly larger than the mouth of your mason jar.

Boil a pot of hot water and fill a large pitcher with ice water.

Hot and Cold Water Science Project

How to do the cold and hot water density experiment

Hot and Cold Water Science Experiment

Fill three jars all the way to the top with ice water.

Fill three more jars up to the top with hot water (but don’t make it so hot that you can’t touch the sides of the jar).

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home.

Dye one cold jar yellow, one blue, and one red. Repeat for the hot jars.

First, do the experiment with the cold water on the bottom.

Place the index card over the mouth of the hot water jar. Press slightly to make a seal.

Flip the jar over and place it on top of the cold water jar (make sure it’s a color combo that will make a secondary color).

Line up the lip of the jars and carefully pull the card out.

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home.

The water will stay separated!

Repeat for the other four jars.

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home.

Carefully grip the center of the jars and flip them. They will mix into secondary colors right away!

If you don’t want the mess risk of flipping the jars, you can simply put the hot water jar on the top and use the index card over the cold water.

Learn about water density, energy, how molecules work, and more in this super fun and easy hot and cold water density science experiment! Kids will be delighted with how fun it is, and the bright colors will many any kid interested in science! It's the perfect STEM activity for the classroom or home.

Then, when you move the card out of the way the colors will mix and you won’t have to flip any jars.

Save this idea for later!