Check out this awesome experiment where you can create your own siphon and witness gravity at work!
Materials:
Two clear cups, a disposable lid, a bendable straw, scissors, any liquid, and a hot glue gun
Time Estimated:
5-10 minutes
Directions:
First, cut a slight angle near the top of your straw. Then, cut the point off and bend it.
With your first cup, make a small hole in the center of the bottom. Make it just big enough for the straw to fit.
Then, push the bottom of the straw through the hole until the bendy end reaches the bottom of the cup. Hot glue the bendy end of the straw to the cup, making sure that air can still travel through the straw.
To prevent liquid from leaking through, apply hot glue around the straw.
Then, place the first cup on top of your second cup and pour in your liquid.
Watch what happens to the liquid once it passes the top of the straw!
Think Like a Scientist:
Why does the liquid stay put underneath the level of the straw?
Conversely, why does the liquid start to drain once it goes past the straw?
How It Works:
In this activity, you constructed a type of siphon known as a Pythagoras Cup! A siphon is any device that allows liquid to flow from one high place to another lower place. This is able to work because of gravity!
Now, before we move on, let’s observe what happens when we experiment with our Pythagoras Cup! First, let’s see what happens if we fill the cup just below the bend of the straw. Then, let’s fill it up far above the straw. What did you notice when you filled the cup to these two different liquid levels? Why do you think the liquid drained only after we poured the liquid above the straw?
As we fill up the cup, the bendy end of the straw starts to fill up as well. The height of the liquid in the cup will always be the same as the height of the liquid in the straw!
Once the liquid level rises above the bend of the straw, the contents will drain completely. This is because when more liquid is added to the cup, the pressure in the straw will increase. When gravity is concerned, liquids always want to travel from high pressure to low pressure. This allows the liquid to be pushed through the straw (area of high pressure) and into the second cup (area of low pressure)!
Now that we know how the cup works, try the experiment again (with a not-so-clear cup), and see if you can trick your friends!
Looking for more fun at home STEM activities for your young scientist? Check out our workbook full of exciting science experiments and empowering activities!
