Everything Kids' Magical Science Experiments Book (15 page)

Start at the letter marked with a dot. Collect every other letter around the circle, clockwise, until you have them all. You will need to go around twice! Read the letters in order to find out what this scientist has discovered.

We didn't tell you which way to go around the circle —you will have to discover that by yourself!

Don't you hate it when you have a balloon all blown up and it unexpectedly springs a leak? All your work is wasted, and try as you might, it's nearly impossible to reinflate a balloon once it's been deflated. But this time you will actually be able to repair a hole in a balloon, hopefully before all the air leaks out. Granted, the fix won't last forever, but it will do the trick for a while at least.

Question: Can you repair a leak in a balloon?

• Medium latex balloon
  
• Penny
  
• Vegetable oil
  
• Small needle or pin
  

1. Place the penny inside the balloon before inflating it.
   
2. Inflate the balloon so that it is more than halfway, but not all the way, inflated. Tie off the end.
   
3. Practice swinging the balloon around so that the penny inside spins around the inside of the balloon. You can best do this by holding the balloon near the knot and letting it hang down.
   
4. Dip the needle in oil and carefully insert it into the end of the balloon opposite the knot. Remove the needle, leaving a small hole.
   
5. While holding the balloon as before, allow the penny to align itself over the hole in the end of the balloon.
   
6. Slowly turn the balloon right side up and the penny should stay in place, effectively sealing the hole.
   

Try as you might to seal a hole in a balloon from the outside, it will most likely fail. Some people try to use a piece of tape, or glue, or other adhesive. But the air inside typically pushes against the seal and the hole stays unpatched. But the penny seals the hole from within because of the difference in air pressure inside the balloon compared to outside the balloon. When you blew up the balloon, you filled it with air that is compressed inside. This produces more air pressure inside than outside. As a result, when the penny is allowed to cover the hole, the higher air pressure inside the balloon pushes outward on the penny, keeping it in place over the hole and preventing any more air from leaking out.

There are a number of variations of this experiment that you can try. For example, you can try other coins to see which are most effective at sealing holes. You can also try dipping the coins in different liquids, such as oil or water, to see if the addition of those liquids forms a tighter seal than the coin alone. Another option is to try poking the hole in different places on the balloon. Is there a reason why you were instructed to make the hole at the end opposite the knot? Finally, you can time the experiments to see just how long the penny seal holds. If you work at it, you might be able to perfect the sealing technique and it could lead to a new way to fix leaking tires!

Question: How do you peel a banana without using your hands?

Peeling a banana isn't the most difficult task ever. But wouldn't it be amazing to be able to watch a banana peel itself? You can, with this activity. You will have to open the top of the banana, just enough to reveal part of the fruit inside. Then you will rely on a difference in air pressure to do the rest of the work for you.

You have already seen a few situations where higher air pressure causes something to be pushed toward lower air pressure. In this experiment, the burning paper uses up some of the available air in the bottle. With less air inside the bottle, the outside air pressure will push the banana down into the bottle. By opening the peel slightly, you allow the banana to be pushed down into the bottle and peel itself.

SAFETY NOTE:
When this experiment is complete, the banana will be covered in smoke and perhaps burnt paper. Please do not eat any food item used in a science experiment.

KIDS' LAB LESSONS

• Glass bottle with a mouth approximately as large as a banana
  
• 1 ripe banana that, when peeled, is about the same size as the mouth of the bottle
  
• Small piece of paper
  
• Matches or a lighter
  
• Adult helper
  

1. Peel back the tip of the banana, exposing the fruit inside.
   
2. Ask your adult helper to carefully light the paper and slide it inside the bottle. Alternately, your helper may be able to place the paper inside the bottle and use the long tip of a lighter to start the paper burning.
   
3. Place the banana, exposed side down, into the mouth of the bottle. Be sure there are no air holes around the banana.
   
4. As the paper burns itself out, watch as the banana begins to peel itself.
   

1. It's possible that the flame went out before the paper was completely burned. Why do you think this happened?
   

   

2. Describe what happened to the banana after the flame went out.
   

   

3. Why do you think the difference in air pressure causes the banana to be pulled down into the bottle?
   

   

4. Why is it important that there are no air holes at the mouth of the bottle? What might happen in this experiment if there were (air holes)?