It is said that Pythagoras, the great Greek mathematician and philosopher, loved not only numbers and letters but also jokes. It turns out that many centuries ago, he invented a cup that you can fill up to a certain level, but if you go over the limit, the cup empties its contents. With this cup, Pythagoras wanted to show others how excess leads to failure.

Surprise your friends and learn through this fun experiment how to create a siphon.

For this fun experiment you need:

✔ 1 glass of water
✔ 1 plastic cup
✔ 1 empty container
✔ Pair of scissors
✔ 1 flexible straw
✔ 1 piece of playdough or hot glue gun
✔ food coloring (optional)

Process

Take a plastic cup and ask an adult to make a hole in the bottom so that you can put a straw through it (this can be done by piercing the cup with the tip of a pair of scissors). Take the straw and insert it through the perforation, making sure that the flexible end forms a curve inside the glass.

⛔To fix the straw to the glass and prevent the water from escaping, surround the straw with a little plasticine or hot glue (the latter, with the help of an adult).

If you like, add a little food coloring to the water and hold the plastic cup over an empty container or another glass. Slowly begin to fill the glass with the liquid. Look closely at what happens when you fill the glass below and above the curve of the straw.

Discussion

When you fill the glass with water, the short end of the straw begins to fill as well until it reaches the same level of water inside the glass. As long as the liquid level does not rise above the top curve of the straw, the liquid will stay inside the glass as expected. But if you add more water, gravity will create a siphon causing all the water to spill out through the long end of the straw.

Did you know that some toilets work on this same principle? When the water level rises high enough inside the bowl, a siphon is created that flushes the toilet.