The 10 Coolest Water Experiments for Kids

It’s a great day when play is also educational! With these 10 water experiments, kids (and supervisors!) can explore some of the most intriguing properties of H2O. These tests are perfect for all ages. Just grab a few supplies (and maybe a towel) and you’ll be well on your way to learning how water works.
1. Watch Objects Float or Sink
One of the fundamentals with water science is asking, “Will it float?” Even little ones can get a kick out of these observations. After they watch a lump of clay sink to the bottom of a water bin, teach then to flatten out the shape so the clay will float. For those bigger kids, run some experiments with fruit. Object density determines whether lemons, limes, and oranges float or sink. You’ll see that an orange floats in water. But when you remove the peel, that same orange will sink! That’s because the rind is filled with tiny air pockets—kind of like a life vest—to keep the unpeeled orange afloat. Lesson Learned: Sure, the orange peel has mass, but density isn’t just about weight.
2. Measure Volume with Sponges
Different types of sponges can hold more water than others. All you need are measuring cups and sponges for this study. Get a collection to test multiple varieties and encourage your little scientists to make a guess or “hypothesis” as to which one will have the biggest capacity. Lesson Learned: This one is all about absorption. (A great lead-in to our next experiment…)
3. Indoor Clouds and Rain Science
Interested in the water cycle? This cloud-in-a-jar experiment is a fun way to learn about rain. Just fill a jar with water—almost to the top. Then cover it with a shaving cream “cloud.” Use drops of blue food coloring to simulate water droplets collecting in the cloud. The more droplets there are, the heavier the cloud gets. (Sort of like the sponge experiment.) Until finally…it rains! Lesson Learned: Water cycle basics. When enough water collects in the clouds, gravity makes the droplets fall down as rain.
4. Water Moves in Mysterious Ways
Rain might drop, but water also has a way of defying gravity. Watch the water travel “uphill” by making a special path between two cups. Simply twist a paper towel sheet into a tight rope or wick. Then place one end of the rope in a cup of water and the other end in an empty cup. Practice patience, and you’ll start to see water crawling up the line! Lesson Learned: There’s an adhesive force at work between the water and the paper towel that actually draws the water up. It’s called capillary action.
5. Use Capillary Action to Dye Daisies
The capillary action process is how plants grow and get their moisture. Water travels up through the roots and spreads through the rest of the plant. You can see it happen right before your eyes with food coloring. Kids can watch the water travel up celery stalks when they’re placed in colored water. With a little more time you can even make a colorful daisy bouquet. Lesson Learned: More capillary action—in action!
6. Make a Rainbow on your Windowsill
With just a piece of white paper, a clear glass of water, and some sunshine, a budding scientist can create their very own rainbow. Just set the water glass on a windowsill and watch the rainbow appear on the paper. Lesson Learned: Rainbows form when light passes through water. That’s why we see them after it rains.
7. Explore the Freezing Process with Salt
Show kids why we spread salt on sidewalks in winter with this easy freezing experiment. Take two identical containers and fill them halfway with warm water. Next, stir some table salt into one of the containers. Add it in slowly until no more salt will dissolve. Label each container (salt vs. no salt) and place them in the freezer. Check back every couple hours to see how quickly each sample freezes. Lesson Learned: Salt affects how ice forms. When left alone, water will freeze at 32 degree Fahrenheit. If you add salt, the temperature needs to be much, much lower.
8. Investigate Air Pressure through Water
Another gravity-defying water study can help kids learn about air pressure. Fill a cup to the very top with water and gently place a piece of cardboard over it. When you turn the cup upside down (preferably over the sink) the water should “miraculously” stay inside! The key is to make sure no air bubbles got in the cup with the cardboard. Lesson Learned: If everything goes according to plan, you’ll see that the air pressure outside is stronger than the pressure of the water inside the cup.
9. Study a Leak-Proof Bag
Okay, so we’re normally all about reducing plastic waste, but this experiment is too cool to pass up. Fill a plastic zipper-lock baggie with water and watch how polymers prevent leaking when you poke them with pencils. (Use caution, people—we don’t want to poke little hands!) Even with the holes, the bag should stay intact and sealed. The polymer molecules seal around the pencil holes to keep you dry. Lesson Learned: It’s not magic—it’s science!
10. Play Music with Water and Wine Glasses
Last but not least, check out resonant frequency with water and singing wine glasses. Start by carefully pouring varying amounts of water in a collection of wine glasses. Then wet your finger and trace it around the rim of the glass. Hear anything? The right amount of pressure and friction will get little scientists (and musicians) studying the way vibrations and frequencies work. Lesson Learned: The resonant vibration of wine glasses tends to fall within the range of human hearing—allowing us to hear unique tones.