Today we will talk about another classic. More than an experiment, it is just a simple science demonstration which only aims to be a trick to entertain the kids and for sure also some adults.
We use balloons in many of our experiments, and this could be a great start for a science session to catch our students’ attention before starting with a different activity.
The idea is to pierce a balloon with a wooden skewer without popping it…Is that possible? Definitely yes. You need a balloon, a wooden skewer (long enough to go through the balloon) and some oil.
Inflate the balloon and tie a knot in the end. Dip the point of the skewer into the oil to make it smooth. And puncture the balloon starting close to the knot you made. You need to do this very slowly , pushing and twisting until you get to pierce the surface.
Now, continue to the opposite side, so that the tip of the skewer comes out of the surface again.The balloon skewer is ready!!
How does this work?
When you pierce a balloon, it usually pops because when the hole is made, the pressure of the air inside the balloon and the tension on the surface, make the hole quickly become bigger, and let the air come out on an explosive way. However, the stress forces on the surface near the knot and in the opposite side are much smaller. So when a hole appears on those parts, it does not get bigger quickly but keeps its size. As this hole is completely filled with the skewer, the air does not come out (or at least not in an explosive way). If you remove the skewer, the air will slowly come out through the holes until the balloon goes flat.
And now that you have some balloons on hand, keep experimenting with them with some of those ideas.