okay yeah
Neil is repeating an experiment which is
quite a famous one where you take a
lighted methane oxygen torch and plunge
it into soapy water so of course when
you put it in it cools down and the
flame goes out so you blow bubbles and
the bubbles contain a mixture of oxygen
and methane a potentially explosive
mixture and when you put a flame to it
it goes off with an enormous bang and
very rapidly fortunately I wasn't there
or my ears would still be ringing
we've already shown you videos with soap
bubbles that just contain methane and if
you like those they burn really quite
gently and in a controlled way in fact
Sam tang has done it on her hands the
heat is not enough really to damage you
now when you do with oxygen and methane
the amount of heat to liberate is
exactly the same methane plus oxygen but
it liberates the heat very rapidly so
you get a big pulse of heat rather than
this gentle burning that you see in
Sam's bubbles the methane is not mixed
with the air and so it takes time for
the oxygen from the air to diffuse into
the gas and so it burns relatively
slowly brilliant in the case of Niels
bubbles first of all we're using pure
oxygen there's no nitrogen from the air
and the methane and the oxygen are mixed
in just the right ratio to burn really
well and they mixed at a molecular level
so once the reaction starts it can go
really rapidly and it's not limited by
the rate at which the gas is mixed so
this is premade for Destruction yes and
so you get a very rapid explosion
it goes so fast that even our
slow-motion camera doesn't see very much
so the take-home message from all of
this is that if you have your chemicals
properly mixed in this case meeting and
oxygen the reactions can go very much
faster if you want an analogy it's like
eating spicy food if you have the chilli
sauce on one side and gently dip in your
food there's a gentle warming up if it's
all mixed in together
the first mouthful is foul so what I
thought we'd do is investigate today an
explosive mixture of methane and air and
to do that we're going to use this very
crude device it's just simply can now me
and Neil have doctored it slightly by
drilling a couple of holes okay one in
the bottom and one in the top