Needle through a Balloon

Have you ever seen someone pop a balloon with a needle? Is it possible to stick a needle through a balloon without popping it?

 
You will need the following materials:

 • balloons

• long wooden or metal skewers

• petroleum jelly

Directions:

*Blow up a balloon – not too full – and tie the opening shut.
*Dip the tip of a skewer in Vaseline and spread the Vaseline along the entire length of the skewer. 
*Insert the skewer with a gentle twisting motion into the end of the balloon opposite the knot. 
*Continue pushing and twisting the skewer until the tip emerges from the other end, near the knot.

If your careful, you can stick the skewer through the balloon without popping it!

*The rubber in the balloon consists of many long molecules that are linked together. It's similar to the way all of the noodles in a plate of spaghetti stick together. These long molecules are called polymers; when molecules of a polymer are chemically attached to each other, it is called cross-linking. These links hold the polymer molecules together and allow them to stretch…up to a point. When the force or tension pulling on the cross-links is too great, they will break, and the polymer will pull apart.

     * Results when inserted through the ends     

*If you place the needle in the sides of the balloon it will pop because there are fewer polymer molecules holding it together.  The rubber at the ends of the balloon is stretched out less than in the middle of the balloon. Therefore, there is less force pulling on it. This allows the tip of the skewer to break some polymer cross-links, push aside the molecules of rubber, and slide into the balloon. 

 
In the side of the balloon, there are fewer polymer molecules. When you push the tip of the skewer through the rubber in the side of the balloon and the skewer breaks a few of the cross-links, the tension on the remaining cross-links is too great, and the balloon pops.

Cautions:

* Any needle used, either wooden skewer or an actual needle, are sharp so make sure younger kids are supervised at all times.

*In case the balloon pops, make sure there is no one stand close to you because the balloon peices can flying in all directions.

Questions:

Why doesn't the balloon pop?

 
Now try to stick the skewer into the side of the balloon.What happens?

 
Does it look lighter or darker than the rubber in the rest of the balloon?

 
Do you think there is a way to stick a skewer through the side of a balloon without popping it?

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