September’s challenge is….
To do the leak-proof bag experiment you simply fill a clear plastic bag (a zip-lock one works well) about 2/3 full of water.
Carefully poke a sharp pencil right through the water and out the other end. No water spills!
Try it with other sharp objects–like kabob skewers!
So, what’s the secret? Zip-lock bags, like other plastics, are made from polymers–long chains of molecules. When you poke through the bag, you force the polymers apart, but they quickly press back as much as possible. As they press towards the pencil, they practically seal the hole you made.
Now, your pencil can always wiggle more space between the pencil and the bag, so you may want to practice over a sink before doing it over someone’s head!
When you’re done, hold the bag over the sink and pull the pencils out. These “fountains” are just as exciting as the leak proof bag!!
Have fun! Why not post a picture of your Science in action on Twitter, or send an email or bring it in to show?