On Sun, 28 Nov 2010 07:59:09 +0000, Ted Frater
wrote:

Are there any chemists here?

Sure are. :-)

I ask because im interested to know why water makes it burn so much
hotter/faster etc.
Could it be that oxidising magnesium splits water, ie hydrogen oxide
into its seperate parts? of oxygen and hydrogen?

Yes, when magnesium burns in steam, or when you have a largish chunk
of burning Mg and throw water on it, the Mg combines with the oxygen
from water and releases hydrogen gas. And the H2 burns in air. Lots
of fun.

Mg + H2O -- MgO + H2

Similar reactions with CO2 and with sand:

2 Mg + CO2 -- 2 MgO + C (soot)
2 Mg + SiO2 -- 2 MgO + Si

IF it does it might just be a keyto maing a car run on water if the
magnesium acts as a catalyst at its burning temperature.

Nope. Say you have a reaction that "goes" but is much too slow, such
as nitrogen reacting with hydrogen to give ammonia. A *catalyst* is
something that makes that sort of reaction go faster. The catalyst is
recovered after the reaction, it is not consumed.

When magnesium burns, it's *consumed*. Gone.

And in case the inevitable question arises....no, you can't
economically fuel a car on magnesium or hydrogen or insert magic fuel
here as long as the fuel chosen is obtained by electricity. UNLESS
that electricity is generated from an inexhaustible source (sun, wind)
or cheap renewable source (plant matter). To make Mg or H2 requires
electrical energy that is exactly equal to (well, MORE than) the
energy obtained by burning that material.

It's the whatever law of thermogoddamics, I forget which one. :-)
--
Best -- Terry