Weird Science: Ulu Ke Kukui

Weird Science: Ulu Ke Kukui

WAIANAE (HawaiiNewsNow) - Dr. V traveled to Waianae to show youth in the community a fun balloon experiment. Check it out!

Dr. V Show: Balloon Science

Things you need:

  • Several balloons
  • Bamboo skewers
  • A little cooking oil or dish soap
  • Water
  • Candle

The experiment:

HOT Balloon

As always, please perform your experiments under the supervision of an adult.

Blow up one of the balloons and tie it off. Light your candle. What do you think will happen when you hold the balloon over the candle flame? Give it a try. Next, fill another balloon with some water, then blow it up and tie it off. Now, try holding this balloon over the candle. What happens?!

Skewered Balloon

Blow up your balloon then let some of the air out and tie it off. Take a skewer and dip it in the cooking oil or dish soap and rub it in along the length of the skewer. Then, push the skewer through the end of the balloon with the knot. You should be able to push the skewer all the way through and push it out the opposite end of the balloon. You've skewered the balloon! What happens when you try pushing the skewer through the side of the balloon?

How does it work?

HOT Balloon

Water is very good at soaking up heat. Because the balloon is very thin, the heat passes through it quickly and heats the water on the inside. As the water near the flame starts to get hot, it moves up, letting cooler water take its place to soak up more heat. This process lets the water balloon absorb a tremendous amount of heat without popping.

The black stuff on the balloon is carbon. It did not come from the balloon. It came from the candle flame. The balloon has not been burned or damaged.

Skewered Balloon

The rubber in the balloon consists of many long molecules that are linked together, 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. The rubber at the ends of the balloon is stretched out less than in the middle of the balloon, and looks darker. Therefore, there is less force pulling on it. This allows the tip of the skewer to break some polymer cross-links and slide into the balloon. In the side of the balloon, there are fewer polymer molecules and they are all stretched out, making the balloon more see-through. When you push the tip of the skewer through the side of the balloon and the skewer breaks a few of the cross-links, the stress on the remaining cross-links is too great, and the balloon pops.

Ulu Ke Kukui

www.ulukekukui.org

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