March 2014

Windbag Challenge – The Bernoulli Bag (3/19/14)

Here’s the challenge… How many breaths do you think it will take to blow up an 8 foot long bag? Depending on the size of the person, it may take anywhere from 10 to 50 breaths of air. However, with a little practice… and some scientific powers… you will be able to inflate the bag using only one breath!

MATERIALS

  • The “Windbag” is a long piece of plastic in the shape of a tube. You can purchase windbags on science supplier websites or you can make your own long bag using a product called a Diaper Genie refill available at major discount stores. We like to make our own at Hands On!, because it less expensive and who has time to wait for the fun?!?!
  • You can do this experiment by yourself, but it’s definitely more fun when you try this with friends or family members!

EXPERIMENT

  1. Cut off a 4-5 foot section of the Diaper Genie bag for kids, or a 6-8 foot section for grown-ups. Be sure to tie a knot in only one end of the bag.
  2. Invite a friend or family member to blow up the bag, keeping track of the number of breaths it takes.
  3. Then, squeeze all of the air out of the bag.
  4. Explain to your friend or family member that you can blow up the bag in one breath. They probably won’t believe you, but that’s all part of the fun and surprise.
  5. Have your friend or family member assist you by holding onto the closed end of the bag. Hold the open end of the bag approximately 10 inches away from your mouth. Be sure to make the opening as wide as you can with the index fingers and thumbs of both hands.
  6. Using only one breath, blow a long, steady stream of air into the bag (like blowing out candles on a birthday cake). You MUST keep your mouth off the bag (about 10 inches away) and keep the opening of the bag as large as possible. The secret is in the open space between your mouth and the bag. If you do it correctly, you will see the bag quickly inflate. The trick is to seal the bag with your hand as fast as possible so that none of the air escapes. Tie a slipknot in the end of the bag or let the air out and try again.

The ULTIMATE Windbag Challenge

  • Blow up multiple windbags, being sure to tie knots on the end of both sides. Work with friends or family to build a large freestanding Windbag structure. The structure can be held up only by the Windbags themselves. (YOU WILL NEED A LARGE OPEN SPACE FOR THIS)

HOW DOES IT WORK?
The long bag quickly inflates because air from the atmosphere is drawn into the bag from the sides along with the stream of air from your lungs. In 1738, Daniel Bernoulli observed that a fast moving stream of air is surrounded by an area of low atmospheric pressure. In fact, the faster the stream of air moves, the more the air pressure drops around the moving air. When you blow into the bag, higher pressure air in the atmosphere forces its way into the area of low pressure created by the stream of air from your lungs. In other words, air in the atmosphere is drawn into the long bag at the same time that you are blowing into the bag.

 

Green Leprechaun Snow (3/5/14)

MATERIALS

  • New, unused disposable diapers (several brands in the same size if possible)
  • Newspaper or thick trash bag (for work surface)
  • Scissors
  • Zipper locking sandwich bag
  • 8-ounce plastic cup
  • Water
  • Green food coloring
  • Salt
  • Plastic spoon or popsicle stick (for stirring)

DIRECTIONS

  1. Put a brand new, unused disposable diaper onto a piece of newspaper or thick trash bag as a work surface.
  2. Cut through the inside lining very carefully and remove all the material inside that looks somewhat like cotton.
  3. Put all the “cotton” material into a clean, sandwich sized zipper locking bag.
  4. Blow some air into your bag and make it puff up, then seal the bag.  Just don’t blow too much air into it, otherwise it may pop!
  5. Shake the bag for a few minutes to remove a powdery polymer from the “cotton”.
  6. Remove the “cotton” from the bag and which will leave behind the dry polymer you just extracted from the diaper.
  7. Pour the polymer into a plastic cup and fill the cup with water.  You can make “Leprechaun Snow” by adding 2-3 drops of green food coloring to your water before adding it to the polymer.  Mix it with your spoon or popsicle stick until the mixture begins to thicken.
  8. After a few moments the polymer and the water create a sort of “gel”.
  9. You can turn your cup upside-down and see how it has solidified.  Be sure to only hold it upside down over your protected work space otherwise it may stain your clothes, floor, or anything else it touches.
  10. Now you get to take it out and play with it on your protected work surface!
  11. Put the gel pieces back into the cup and push them down with your fingers. Add a teaspoon of salt, stir it with a spoon and watch what happens. Salt messes up the gel’s water-holding abilities. When you’re finished, pour the salt water goo down the drain.
  12. Grab a new diaper and slowly pour about 1/4 cup of warm tap water into the center of the diaper. Hold the diaper over a large pan or sink and continue to add water, a little at a time, until it will hold no more. Keep track of how much water the diaper can absorb before it begins to leak.

HOW DOES IT WORK?

The secret to the “Leprechaun Snow” is a polymer called sodium polyacrylate, which is superabsorbent. A polymer is a long chain of repeating molecules.  “Poly”=many, “mer”=parts.  When superabsorbent polymers come in contact with water, they begin to expand because water is drawn in and held by the polymer’s molecules. In other words, the polymers are working together to act like one gigantic sponge!

A diaper contains the “cotton” to help spread out the polymer throughout the diaper for catching any “accidents”.  That way, the baby doesn’t have to sit on a gross, squishy pile of wet gel. A small amount of the polymer will hold a large amount of water, but it does have its limits.  At some point, the baby would be sure to let you know that the gel is full and it’s time for a new diaper!

NOW TRY THIS!

A good experiment has a variable, something that changes, and then you can compare the results.  Try changing the brand of diaper (be sure to use the same size).  Test a variety of diapers out to see just how much water they will absorb.  Compare your results to the absorbency of the first diaper you tested.  Everything in your experiment needs to stay the same except for the brand of diaper. You’ll find out extremely quickly if you get what you pay for or if there really isn’t a difference between the brands.