Let’s do some science with WATER! In this experiment, we’re going to make a working water fountain with a 2 liter soda bottle and some simple supplies from around the house. This water fountain works by using air pressure to make the water flow. It’s such a fun project, and you can make it work over and over again.
This water fountain science experiment is fun for preschoolers all the way up through middle schoolers. Little kids will think it’s a blast! Older kids will be able to do this project on their own and really understand the concepts.
The inspiration for this water fountain came from Learn with Play at Home. It’s such a brilliant idea!
This project is just silly fun for a hot summer day, but it also demonstrates important science concepts. Use this activity to go with a study on matter. It’s the perfect way to demonstrate that air is matter because it takes up space.
- 2 liter soda bottle
- Plastic bendy straws – 4 or so
- Hot glue
- Balloon – we used a 9 inch balloon, but a smaller one will also work
- A container for catching the water
- Food coloring (optional)
- Drill or something to make a hole in the plastic bottle
You can do this experiment outside with no container to catch the water, but one big benefit of the container is that you can reuse the water over and over.
Step 1: Prepare the Water Bottle
Drill a hole in the water bottle that is the same size or slightly bigger than the straw. If the hole is too small, you’ll have to collapse the straw to get it in. If the hole is too large, you can easily fill the gap with some hot glue.
Step 2: Add a Straw
Insert the straw into the hole in the bottle so that the straw is angled down toward the bottom of the bottle. You want the bendy end of the straw to stick out of the bottle.
Secure the straw with hot glue. Use extra glue on the underside of the straw to support it at the proper angle.
Step 3: Start up your Fountain!
We used the same under-the-bed tub that we used for our Ocean Science Experiments. We also colored the water blue just for fun, and to make it easier for you all to see what’s happening in the pictures.
Fill your bottle with water.
You’ll notice that if the height of the water in the bottle exceeds the height of the straw, water will start flowing out of the straw.
In the picture below, the height of the water in the straw is equal to the height of the water in the bottle.
If you tip the bottle a little, water will pour out. But it won’t flow out on its own unless you tip it.
Now blow up the balloon. Pinch off the balloon to keep the air from flowing out, and stretch it over the top of the bottle.
The air in the balloon will push down on the water in the bottle and force it out of the straw! Impressive!
The Science Explanation:
The air will leave the balloon because the air pressure inside the balloon is higher than the air pressure inside the bottle. As air flows into the bottle, the air pressure increases, which puts pressure on the water. This pushes the water up the straw and out of the bottle with a surprising amount of force!
The water fountain is a lot of fun to play with! Kids will definitely want to try this more than once.
Variation: Make a Water Tower
We decided to lengthen the straw by connecting more straws. We put a small piece of duct tape around each connection. Then we could pretend that our bottle was a water tower sending water through the pipes (straws) to a building. We added a separate container to be our building.
Real water towers use the force of gravity to make water flow. A pump fills the tower, and then the water flows out of the tower and through the city pipes because of gravity. I’ll link a very helpful video below!
Because of the pressure of the air rushing out of the balloon, we were able to get the water to flow uphill in the straw, and then back down again.
It was interesting to observe that when the water level was low in the bottle and the pressure started to drop, we could lift up the bottle and greatly increase the pressure. This was gravity at work, just like a real water tower!
Here’s a really interesting YouTube video that explains how water towers and city water delivery work. This is so well done and easy to understand!
Need more science experiment ideas?
Be sure to check out our Ocean Science Experiments for more science activities with water.
And here’s another awesome way to demonstrate that Air Takes Up Space.