Learn how to keep water from flowing through a screen.
Don't throw away that plastic mesh bag from the grocery store used to sell onions and potatoes. You'll amaze your friends with this cool experiment that defies gravity and uncovers the mystery of surface tension.
- Plastic mesh bag used for produce at the grocery store
- Wide mouth bottle
- Rubber band
- Index card
- Pitcher of water
- Bucket to catch the falling water
- Plastic mesh bags come in all shapes and sizes. The mesh bags used to sell small onions or cloves of garlic seem to work well. Cut a piece of mesh from the bag large enough to drape over the mouth of the bottle.
- Stretch the mesh over the bottle and use a rubber band to secure it in place.
- Fill the bottle with water by pouring the water through the screen. This proves to your friends that the water easily flows through the screen. Fill the bottle almost to the very top.
- Cover the bottle with an index card. Hold the card in place as you turn the card and the bottle upside down. Slowly remove the card from the opening and the water mysteriously stays in the bottle. Oh, did we mention that you should probably hold the bottle over the bucket? Or you can just hold the bottle over your friend who is holding the bucket.
- Tip the bottle slightly to the left or right and the water will fall. Shake the bottle and the water will fall. Touch the screen and the water will fall. It might be a good idea to tell your friends about this so they have a chance to run.
- If you have a very steady hand, try this. While the bottle is turned upside down and the water is defying gravity, gently feed a toothpick through one of the screen holes without breaking the water seal and watch it float to the surface. Okay, this is easier said than done, but be sure to watch the video of Steve Spangler doing this.
How does it work?
If you dip a piece of the screen (the mesh bag) into a glass of water, you notice that the water fills the screen holes. A force called cohesion, which is the attraction of molecules that are the same to each other, causes this effect. The surface tension “membrane” is always trying to contract, which explains why falling droplets of water are spherical or ball shaped. The water stays in the bottle even though the card is removed because the molecules of water are joined together to form a thin membrane between each opening in the screen. Tipping the bottle or touching the screen will break the surface tension and surprise everyone with a gush of water!
Water Jar Wonder
August 29th, 2011
Click the thumbnail below to see the video.
adolsk polonski - May 21, 2010
Simple and Efficent. Thanks we got an A+ because of you.