You may have heard you can drain a fish tank with a siphon, but have you ever made one, just for fun?
With a few feet of clear, plastic tubing, you can create your own siphon, make a “roller coaster” for small objects,and watch physics in action.
You’ll need a long piece of flexible, plastic tubing (maybe 5 feet), a large container set off the ground, and another container to catch the water so you can reuse it. A hose is also helpful, if you’re outside.
Fill the upper container with water and put one end of the tube UNDERWATER in this container. For the siphon to work, one end must be submerged under water in the upper container and the other end must be lower than the level of the water! You can weight the upper end down to keep it submerged.
There are several ways to start the siphon. You can submerge the entire piece of tubing in the water to remove all the air, put your thumb over one end, remove it from the water and lower it below water level before removing your thumb to start the flow. Alternately, we’ve found it’s easiest to put one end of the tube in the upper container, have the other end out and lower than water level and then put the running hose to the underwater, upper end of the tubing to remove all the air and start the water running out of the lower end. Remember to keep the upper end underwater or your siphon won’t work!
You can put tiny objects at the mouth of the siphon and watch them get sucked through from one end to the other. We wrapped our siphon around a broom handle to make a water ride for broken water balloon fragments.
Exactly how siphons work is a little bit complicated, but it has to do with atmospheric pressure and gravity, which give the water in the upper container more potential energy than the water in the lower container. This energy allows the water in the siphon to essentially flow “uphill” for a short distance before it drops to the lower container. You can go to “Ask a Physicist” for a more detailed explanation.