Sunday, January 17, 2010

Banana Split - Experiment #329

"Can you place a banana in a bottle without using your hands? Amaze your friends with this party-trick science experiment. Watch carefully, because the banana is quicker than the eye in this split-second surprise. Moreover, it all has to do with molecules and air. Careful - boiling water involved! Also, it is best to do this in the sink.

You will need:
1/2 banana, peeled
teakettle with boiling water
clean, long, narrow bottle with banana-size mouth
dish towel

What to do: Put the funnel into the bottle neck and carefully fill the bottle almost to the top with boiling water (adult help recommended). Remove the funnel. Wrap a dish towel around the bottle and gently swirl the water around; then pour it out. Quickly, fit the pointed end of the half-banana downwards into the bottle neck so that it makes an airtight plug. (Watch the variables - the size of the banana and bottle neck, the amount of hot water, the time it takes - and be patient! You may have to do this experiment several times to get it right, but you will succeed!)

What happens: The banana is sucked down into the bottom of the bottle.

Why: The heat from the boiling water causes the air inside the bottle to expand, forcing some of it out. When the banana is placed into the mouth of the bottle and the cooling air inside the bottle shrinks again, the air pressure inside is reduced and the greater air pressure outside shoves the banana ahead of it into the bottle. This gives you an idea of what happens when air is removed from a space and nothing takes its place (partial vacuum). Just small differences in air pressure can cause things to move.

What now: You want to recycle the bottle, but the banana is inside it! WHAT CAN YOU DO? Just wait a few days. Let the bacteria in the banana do their chemistry work. Bacteria give off enzymes that break down proteins and starches. The banana will eventually change chemically (ferment) and soften enough to be removed easily." If a monkey tries this, he would want to get it out immediately to eat it!

What happened when CKS tried it?: It worked on the first try! The banana was going so slow, you had to squint a little to see it moving into the bottle. And wait a sec....when it gets in the bottle, it goes 'BOMP'! It sucks in really fast and scares you a little.

CKS rating: 4 stars - Like 3 ice cream cones!

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