Simple Siphon

How Does a Siphon Work?

 

Materials

• scissors
• plastic tubing
• 2 plastic bowls
• 2 or 3 books
• tap water
• food coloring

Try This

1. Cut a piece of the plastic tubing about as long as your arm.
2. Place the first bowl on the books.
3. Pour tap water into the first bowl and add a few drops of food coloring.
4. Place the second bowl on the table. The tubing should reach from one bowl to the other.
5. Place one end of the tubing in the colored water. Suck on the free end of the tubing until all the air is removed and the tubing is full of water. Hold your tongue over the end of the tubing to keep the water in place.
6. Carefully remove the end of the tubing from your mouth and hold your finger over the end as soon as your tongue lets go.
7. Place the end of the tubing in the second bowl.
8. Remove your finger. What happens?

What's Going On?

When you removed your finger from the end of the tubing, the water steadily flowed from the upper bowl to the lower bowl. This is how a siphon works. The water kept moving through the tubing once it started because the pressure of the air on the water in the upper bowl pushed the water down the tubing. The weight of the water in the long end of the tubing also pulled the water down. Also, water is attracted to itself; hence, as it flows out, it pulls the water behind it, like a train of elephants holding each other's tails.