From: utzoo!decvax!yale-com!leichter
Newsgroups: net.physics
Title: Re: Smothering a Candle
Article-I.D.: yale-com.590
Posted: Thu Dec 23 10:03:33 1982
Received: Fri Dec 24 05:46:41 1982
References: rabbit.1013

Well, the return of an old problem.  The explanation isn't incorrect, it's
just incomplete.  As the candle burns, it converts the oxygen in the jar
into carbon dioxide, and some water vapor.  The actual change in volume
of gas would be complex to calculate, I'd expect - each O2 in the air
that gets turned into CO2 is a 1-1 molecule sway; but the O2 to H2O reaction
is 1 to 4.  HOWEVER, CO2 is quite soluble in water, and the H2O probably
condenses out, too; so the net effect is that these gases disappear from
the gaseous phase into the water, the amount of gas in the jar decreases,
and the water rises.

This explanation is still only approximate, of course; the burning candle
also gives off a lot of complex organic molecules.  There are limits to
physics and chemistry, however...

What's "right" about the standard explanation is that the water does, indeed,
rise to take the place of oxygen that's no longer in the gas; and, in fact,
the amount of rise is about what you'd predict based on the percentage or
\\\of O2 in air.  You can demonstrate that CO2 is going into the water, I
believe, by dissolving lime (not the fruit) in it first; it will then turn
cloudy as CO2 is added.
							-- Jerry
						decvax!yale-comix!leichter
							leichter@yale