So, we’re braving the elements Brady, to repeat the experiment that we did quite some
time ago, so you will remember that we had a very small balloon of hydrogen
Match on a stick to hydrogen, big bang coming!
Are you ready?
Yep!
Here we go!
And the fact that we’ve come outside, might actually give you an idea of what we are going
to do, cause we are going to make it a little bit bigger, so let’s go and fill a balloon.
Alright, cool.
Well, hydrogen, I think is very important because, it is the simplest atom, it’s the
atom, consists of a positively charged proton which is relatively large and a negatively
charged electron, that goes round it.
Electric match?
I think an electric match will go well on that.
Yep.
Oh, look at the tension on the balloon!
Hold it, I’ve really gone for it and blown that one up.
The tension!
What happens is that hydrogen is reacting with oxygen and H2 plus O2 reacts to form
H2O and an oxygen atom and then that oxygen atom goes on to react with another hydrogen
molecule to make more water and the reaction generates a lot of heat and that heat, heats
up more gas to make it react faster, so you generate more and more heat, so the reaction
that begins quite slowly with the first few molecules, runs away and that is why you get
the explosion.
So here we have a rather large balloon of hydrogen, Neil is just preparing our electric
match which we are going to attach to the side of this balloon.
And some of the biggest explosions in the 20th century, the Chernobyl reactor, the space
shuttle that blew up when it was taking off, were in fact explosions caused by hydrogen
and oxygen.
So we’ve filled up a balloon of hydrogen, and I think if you look at the hydrogen balloon
you will see that it is slightly larger than those we have attempted before. Now we are
going to try to detonate it or burn the hydrogen, in the air by giving it a match and the match
we are going to use is again an electric match, which is connected to our detonator box.
If you stick a pin in the balloon, the balloon will burst because the rubber will break,
but the hydrogen will come out and it won’t react with the oxygen because the hydrogen
is cool, it’s at the same temperature as the air, but the reaction of hydrogen and
oxygen like many reactions involves so called activation energy, you have to put in a certain
amount of energy to get it going. But once you get it going, you get more heat coming
out, than you put in to start it off.
So, let’s arm the circuit, 5-4-3-2-1.
That was more like it.
Lovely!
When Pete puts the match to the balloon, first of all the match burns a hole in the balloon,
and then the heat gets the hydrogen and oxygen near the outside of the balloon and they start
reacting and the heat then spreads through the volume of the hydrogen and oxygen, faster
probably than the balloon is bursting and as it spreads through the temperature builds
up and up and up because you are generating so much heat.
The reason that you hear a noise, is because, it causes a rise in pressure which sends a
pressure wave out through the air and it hits your ears or the microphone on your camera.
I honestly don’t know why you see any colour. I suspect that the colour may actually be
caused by the burning balloon which contains carbon and is really like the flame on a candle.
Because normally when you have a hydrogen/oxygen flame you don’t see any colour at all. Alternatively,
it may be some impurities in the gas, but I suspect that what you are seeing in the
fire ball is just the burning of the balloon. The other thing which is really quite exciting
about hydrogen is that in principle if you heat hydrogen to really high temperatures,
you can get two hydrogen atoms to fuse together, or rather, it will not work with hydrogen,
but it will work with a heavier form of hydrogen which is know as deuterium where instead of
a proton and an electron, you have a proton and a neutron, which is a neutral particle,
and an electron, and two molecules of deuterium can fuse together to make one atom of helium
which has two protons, two neutrons, and two electrons and this produces a lot of energy.
It is the basis of the so-called hydrogen bombs, which are like super atomic bombs,
but which require an enormously high temperature to get the reaction to go.
You can probably hear it hitting and fizzing into the bottle there.
There is great hope that in the end much of the world’s energy crisis can be solved
by doing this so called nuclear fusion of deuterium to make helium which would produce
energy extremely cleanly.
So here, we’ll just tie it off, if my Welsh hands can actually tie a knot on a balloon,
‘cause, you know we are all a little bit bizarre.
Deuterium gas, in all its properties, will be very similar to that of hydrogen, of course
it is denser, because it has a neutron as well as a proton but it is still much lighter
than air so a deuterium balloon will still float up to the ceiling and make Pete look
just as stupid as the hydrogen one.
You’ve got to keep hold of it.
Or you lose it
Or you lose it, you know!
I was thinking more of fusing it, that sounds like a really big explosion we could do out
the back.
No! Fusing reactors are way beyond what Pete can do unless he is a lot cleverer than I
think.
I got a balloon! I had a balloon of hydrogen!
That is the second time you have done that!
Now it’s going to go up there eventually anyway!