Re: Forwarded mail....

Date: Mon Dec 30 2002 - 18:57:27 PST

Hi Jen


When you breathe helium the pitch of your voice goes up.
This is because the resonant frequency of your vocal apparatus is increased due
to the speed of sound (molecular velocity) increase, due to the light molar mass
of the helium. (Many people claim that this increase is due to the vibration rate
of the vocal chords but this is an error.)

You can quantify this problem by measuring the resonant frequency of a coke
bottle full of air (29 grams per mole) Then finding the resonant frequency of the
bottle full of helium. ( 4 grams per mole) Of course you'll have to play the
bottle while hanging upside down so that the helium stays in the bottle, but this
should greatly entertain your teacher.

A musician can give you the pitch change as well as a frequency meter.

The resonant frequency is proportional to the speed of molecular motion.

Paul Doherty

> ________________________
> Deb Hunt
> Snacktalk Moderator
> Exploratorium
> 3601 Lyon Street
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> ---------- Forwarded message ----------
> Date: Tue, 3 Dec 2002 16:45:23 -0800 (PST)
> From: Jen Wetmore <>
> To:
> Hi, my name is Jen and i am in 11th grade chemistry. I am looking for an experiment to
prove the relationship between molar mass and gas particle velocity that i could
do in the
classroom. Do you have any suggestions? Thanks
> Jen
> ---------------------------------
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