Water Power

The dog days of summer are upon us. We have been playing in water of one form or another every single day. There is the beach, the splash parks, the sprinklers, the swimming pools…and science experiments.

This experiment, constructed of very simple supplies, demonstrates how a hydroelectric power station works. Many dams produce hydroelectric power by harnessing the incredible power of falling water to turn enormous wheels (called turbines) that then drive machines (called generators) that produce electricity. The Hoover Dam is one of the largest dams of this kind, providing electricity to Arizona, Nevada, and California.

This idea came from 50 Science Things to Make & Do, one of our very favorite science activity books. Ready to see how water power works? Let’s get started.

Total Time: 30 minutes to make your bottle, then only a minute to do the experiment
Safety Concerns: An adult will need to do the cuts in the bottle. Because the plastic is slippery, cutting it can be dangerous for anyone!

Materials You Need:
A two-liter bottle
2 straws, cut into 1-inch long pieces
A pitcher full of water


  • Cut the top off the bottle. If there are sharp edges be sure to put some tape over them so nobody gets hurt!
  • Using the thumbtack, poke six holes around the base of the bottle. Use the pencil to widen the holes. Don’t be dainty here, it takes some real muscle to make those holes!
  • Push a straw piece into each hole and secure it with tape.
  • Make three holes at the top of the bottle and tie a piece of string through each hole. Each string should be about the same length.
  • Tie all the strings to a fourth piece of string at the top.
  • Making sure you are outside or in a bathtub, pour water into the bottle and watch it spin as the water pours out of the straws!

Print These Instructions

Check out our video when we did this experiment. I apologize in advance for the background noise: we live on a very busy street! When we do this experiment again we are going to put the holes for the straws lower. We found that the more water in the bottle, the faster it spun around, so putting the straw holes further down should make it spin faster. It would also be fun to experiment with bottles that are taller/shorter and see if it makes a difference if you put more or less straw holes in the bottom. We have a lot of hypotheses to test!

Want more plastic-bottle-inspired fun? Check out the amazing upcycling some people are doing with their two-liter bottles and caps.
Also makes a great bath toy! Or a tacky Christmas tree ornament!

TGIF Linky Party hosted by 123Homeschool4Me

Head on over to 123Homeschool4Me to get tons of free kid activities for the weekend!

2 responses to “Water Power

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