[UAGCNews] Krampf Experiment, Why Thing Go Bang

Fri Apr 25 14:21:09 CDT 2008

If you have kids who love to do experiments - Robert Krampf sends
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Robert Krampf's Experiment of the Week
Why Things Go Bang!

Success! (I hope!)  If you got this, then the new mail system is
working.  If you did not, then please let me know as soon as you
don't get it.  (smile)  In reality, I will know, because the
emails will all bounce back to me.  I am using a new program,
Mail Machine Pro, which will replace Yahoo Groups and Topica.
This should fix the problem of people being bumped off the list
repeatedly, and correct several problems on my end of things too.

Coming Soon!  Member's section of krampf.com
For a small fee ($19.95/year) members will get:

1.  At least two (2) member's only videos per month.  These will
be either additional Experiment of the Week videos, or new videos
from my Basic Concepts in Science, Cabinet of Curiosities, and
Science Sites video series.
2.  Access to the Experiment of the Week videos without the
Google ads
3.  Access to an archive of the past Experiment of the Week
emails, all rewritten and sorted by subject, to make it easy for
you to find all the experiments on sound, chemistry, etc.
4.  The chance to help support my efforts to make science fun.
Your membership fee will help me create more content for both the
member's and public parts of the website.

The public side of krampf.com will be free, as will these
Experiment of the Week emails.  There will be fewer free videos,
but you will still get at least two (2) per month.   

What's New This Week:
    Video:  Why
<http://krampf.com/newsletter/clink_track.php?cust_id=13967&link_
id=5>  Things Go Bang

Why Things Go Bang

Most sounds are caused by vibrations, but think about the sound
of a firecracker going off.  Now think about lightning, popcorn,
and explosions.  All of them make sudden, loud noises, and all
those sounds are the result of air getting bigger.  That's right.
Just air getting bigger.  

To explore that, you will need:

a balloon
something with a sharp point
one of the plastic canisters that film comes in (You can also use
a plastic pill vial, with a snap on cap.  Don't use one of the
child-resistant caps, because it won't work.)
vinegar
baking soda
tissue paper

First, blow up the balloon.  What is in the balloon?  Air, right?
The air in the balloon is being squeezed, making it smaller than
it usually is.  If we let the air out of the balloon, it will get
bigger, expanding to its original size.  If we let the air out
slowly, it expands slowly, and does not make much noise.  On the
other hand, if we took something sharp, like a pin, and made a
hole in the balloon, it would rip, letting the air get bigger
very quickly.  As the air expands, it pushes the air around the
balloon out of the way.  That air pushes on the air beside it,
which pushes on the air beside it, causing a wave of pushed air
to move out in all directions.  When this wave of pushed air
reaches your eardrum, you hear a loud sound.  The more the air
expands, the bigger the push and the louder the sound.  Ok, you
can pop the balloon now and hear it for yourself.  

Another way to see that the bang is caused by expanding air is to
make a pop with a plastic film canister.  Take a small piece of
tissue paper and put about half a teaspoon of baking soda into
the center.  Fold the sides in and twist it to make a small
package that will contain the baking soda and is small enough to
fit easily into the film canister.  Put about a teaspoon of
vinegar into the canister.  Have the lid ready.  Drop the packet
of baking soda into the vinegar and quickly put on the lid.
Stand back and watch.  After a second or two, the cap will fly
off the canister, with a loud pop.  Try it again, without the
lid.  Does it make a pop?

When you mix vinegar and baking soda, they give off a gas called
carbon dioxide.  That is what makes all the bubbles.  With the
cap on, this gas is trapped inside the canister.  As the chemical
reaction makes more and more gas, the pressure builds up.  Soon,
the pressure is enough to pop off the cap, letting the gas expand
suddenly.  That produces the push to make the wave that your ears
hear.

The same idea applies to firecrackers, lightning bolts, popcorn
popping and many other sounds.  They involve gases expanding very
suddenly, producing the wave and causing a bang.  You can even
hear a sound from the expanding gases when you open a can of
soda, and from the tiny pops of the bubbles in the foam popping.
That sounds like a nice experiment for a warm spring day!

Have a wonder-filled week!

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