We’re getting into the hottest part of the summer and there is no place my kids (and me) would rather be than in the water when it’s hot outside. Anywhere near the water is perfect for us: playing in the splash pad, swimming in the pool, running through hose water and sprinklers in the backyard, boating on the lake, and doing science experiments that (might) get you wet!

We had a blast trying these three fun and easy water science experiments. The kids got wet, which of course made them enjoy them even more!  A lot of science experiments we find are for older kids, so I searched and searched to find these experiments which would be fun for my 4-year-old and 1-1/2-year-old and these perfectly fit the bill.

Let’s talk about water

Water is a natural resource that gives us life. It is vital to life on Earth, and as I have discussed in my Earth Day STEM for Kids post, I am already trying to teach my kids the importance and value of water and how to do their part for conservation.

Water is a polar inorganic compound composed of one oxygen molecule and two hydrogen molecules. Water can exist as a solid (at temperatures below 32°F), liquid (between 32°F and 212°F) and gas (above 212°). I have more information about the changing states of water in my ocean themed STEM for Kids post.

The three water experiments I’m presenting today are: Create a spinning bottle powered by water, Combining water streams, and Puncturing a bag of water without spilling a drop. We’re going to talk about the properties of water that make each of these experiments work at the end of each experiment below.

Water Fun Experiment 1: Create a spinning bottle powered by water

This experiment demonstrates how water can create enough power to spin a bottle. This is a fun observational experiment for toddlers ages 1+. The preparations should all be done by an adult, but the kids can help pour the water into the bottle to make it spin during the experiment.

Materials needed:

  • 2 liter plastic bottle
  • Push pin
  • Sharp pencil
  • Straw
  • Scissors
  • 4 pieces of string
  • Water


Cutting the top off the bottle with scissors and poking the holes in the bottle should be done by an adult. The sharp objects can be dangerous for small children because they may not understand how to safely handle and use them.


  1. Mark a line about 1/3 of the way down from the top of the bottle, then use this guide to cut the top off the bottle. I found it helps to poke a hole first and use this starter hole to work your scissors in to cut off the top.
  2. Use the tip of a push pin to poke 6 evenly spaced holes around the bottom of the bottle and 3 evenly spaced holes around the top of the bottle. Use a sharp pencil to widen the holes.
  3. Cut a straw into 6 evenly sized pieces.
  4. Push each straw piece into the holes created in step 2, and secure them with tape.
  5. Tie a piece of string through each hole in the top of the bottle and tie the 3 pieces of string together to a fourth string.
  6. Hold the bottle from the top of the 4th string, then pour water into the bottle, filling it to the top.
  7. The bottle will spin as the water pours out of the straws.

What happened:

Flowing water is a powerful energy source. Standing in a fast-moving stream or in the waves on the ocean shore, you can feel the power moving water can create. This experiment uses the energy from moving water to spin the bottle. It is a similar principle to what is applied at hydroelectric power plants. These plants collect waters in a dam, then control the release of water to turn turbines (giant wheels), then a generator powered by the turbine produces electricity. Old wooden water wheel with blades or buckets that help collect the water and propel the wheel were the predecessor to the modern turbines.

***This experiment is adapted from Usborne Activities “50 Science things to make and do”.***


Water Fun Experiment 2: Combining water steams

This experiment demonstrates the cohesive nature of water by combining six separate streams of water into one stream. This experiment is another fun observational experiment for kids ages 1+.

Materials needed:

  • 1 liter plastic bottle
  • Push pin
  • Water


Poking holes in the bottle with a push pin should be done by an adult. The sharp push pin can be dangerous for small children to be around because they may not understand how to safely handle and use it.


  1. Fill the bottle with water and tightly screw on the cap.
  2. Use the push pin to poke 6 tightly spaced (~1mm apart) holes in the bottle, about 1/4 from the bottom of the bottle.
  3. Unscrew the cap to release the water.
  4. The water will be flowing out in six separate streams – run your finger through the streams to make them combine into one large stream. This works best the closer your finger is to the bottle.
  5. Run your finger through the streams again to break the cohesive force and return to six separate streams. For best results, keep your finger very close to the bottle while running it through the streams of water.

What happened:

In this experiment we’re demonstrating cohesion. Cohesion is the attractions of molecules to other molecules of the same kind. Water has especially strong cohesion due to its polar nature and ability to form strong hydrogen bonds with other water molecules. When you run your finger through the streams it causes the separate water streams to combine into one. When you run your fingers though the water streams again, it breaks the cohesive forces separating the streams again.

***This experiment was adapted from Steve Spangler Science ***


Water Fun Experiment 3: Puncturing a bag of water without spilling a drop

This experiment is actually more about the polymer science of the plastic bag than about water. The flexible polymer chains in the plastic bag prevent the water from leaking through the pencil holes. This experiment is another fun observational experiment for kids ages 2+.

Materials needed:

  • Gallon size plastic bag
  • Water
  • Sharp colored pencils


Before you let your children try this experiment, have a talk with them to make sure they understand how to properly handle the sharp pencil. These are the safety tips I used when talking with my kids: hold the pencil close to the tip, face the tip downward and away from people at all times, and do not walk or run with it.


  1. Fill the plastic bag half full with water and seal the bag closed.
  2. Holding the top of the bag with one hand, use your other hand to push the very sharp pencil in one side of the bag and out the other (without spilling a drop).

    I’m so excited that it worked!

  3. Let your preschooler try it themselves and be amazed. My children were timid to try this at first, but after they watched me push a couple of pencils through they were both very excited to try it and did great! 
  4. Let the kids pull all the pencils out to observe that the holes do not close and water begins leaking out of the bag. Plan to have a few extra gallon size bags available. My kids had so much fun with this experiment we probably repeated it about 3 or 4 times.

What happened:

The plastic bag is made out of a polymer (low-density polyethylene). It is commonly used because it is inexpensive, light, strong, flexible, and traps moisture. When you insert the pencil though the bag, the flexible nature of the polymers allow them to form a seal around the pencil preventing water from leaking.

This experiment works best when you confidently push the pencil though in a strong and swift motion. You might notice that if you don’t quickly and cleanly push the pencil though both sides, it will leak. In a few of our attempts my kids and I pushed the pencil in too slowly and did not easily puncture the back side, and we got leaks. This is because once the polymer has been damaged and a hole was created that was larger than the pencil diameter. The Polymer could not return to its original form, so the water leaked.

***This experiment was adapted from Steve Spangler Science ***



We had so much fun learning and getting a little wet with these fun experiments. As you can tell from the photos, I think I may have had more fun than the kids doing these experiments (especially the poking the pencil through the bag experiment – it was so exhilarating when it worked!).

I hope you’ll give them a try in your backyard on a hot day like we did. Afterwards, you can feel good knowing you are instilling an early love for science in your kids by teaching them science is interesting and fun. I love hearing from you. Let me know if you try any of these experiments and how your kids liked them in the comments below. 🙂


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