Neal's been really active and he and
he's ordered in a special piece of co2
for us which he's going to get out of
the box now so we're going to cut the
co2 and a half so here Neil's cutting
the the co2 now with a saw and this is
the typical saw that you might find in a
hardware shop or a do-it-yourself shop
so and what we're going to do today is
we're going to use this as a reaction
vessel and we're going to burn some
magnesium inside it by containing the
magnesium turnings in co2 we're going to
be lighting or we're going to be
oxidizing the magnesium in essentially
an oxygen-free atmosphere because the
magnesium is going to steal the oxygen
from the carbon dioxide there can be few
people who haven't heard about co2 and
global warming if you have the Sun here
and there is light coming out of the Sun
mostly visible light or just light that
is just into the infrared it goes
through the atmosphere which is
transparent and is absorbed by the
surface of the earth which gets hot and
because everything that is hot gives out
heat ray heat or energy at some sort of
wavelength the heat comes out from the
earth but at much longer wavelength of
light than from the Sun because the
earth is much cooler than the Sun and it
comes out at a wavelength that can just
be absorbed by the co2 so the co2 in the
atmosphere absorbs it and stops it
getting out it doesn't stop all of it
getting out but the more co2 you have in
the atmosphere the more infrared that is
absorbed and the higher the heating
temperature on the atmosphere so on the
earth the temperature on the surface is
quite a pleasant 15 degrees centigrade
or whatever the sort of temperature we'd
like to live at on the planet Venus
which is much close to the Sun which has
a huge amount of come dioxide in the
atmosphere
this temperature the surface is several
hundred degrees centigrade so it's
really hot and baking and if that wasn't
bad enough there's sulfuric acid in the
atmosphere as well just to spice it up a
bit yep
and now we've placed on the top of our
crucible so the co2 is stopping the
oxygen from the atmosphere getting in so
the magnesium is now nicking oxygen from
the co2 reducing it to carbon and using
that oxygen to oxidize the magnesium
oxide there is no argument among
scientists about the fact that co2 does
cause warming of the atmosphere the
argument at the moment is how much of
the temperature rise that people have
seen in recent years is due to carbon
dioxide but clearly the more carbon
dioxide you have in the atmosphere the
higher the temperature is going to be
and my personal opinion is that we are
causing this calm dioxide in the
atmosphere by burning out fossil fuels
which cannot be replaced and if we use
less fossil fuels it has to be a good
thing and so if it turns out that it is
a scare and that global warming is not
as serious as most scientists believe we
won't have lost anything because we'll
have much bigger reserves of fossil fuel
than we would have otherwise so we have
nothing to lose and we have a lot to
gain because if the scientists are right
and there's a 90% chance that they are
right that there are disastrous
consequences of going on as we are
I think should we do it again and we can
put some more spanked into it yeah what
do you reckon new so we going for take
two because we enjoyed the reaction so
much and I'm we've invited Martin down
to come and have a look because he told
me he's never seen this reaction before
so I'd like to see the look on his face
now I've never seen this at all quite
excited
that's really good never seen that
before and yeah I'm very pleased by once
and I what's inside yeah so we'll have
to wait for it to cooler yeah now you
can see the chemical reaction still warm
so it's cooling down but we can see that
there's two real products or two new
compounds inside a white one on the top
which is magnesium oxide and if we bury
in a little bit further or look
underneath we can see a very dark gray
or black one and this is elemental
carbon
so you can have some good fun with co2
as well because if you take a small
piece and then place the coin on the co2
the co2 takes the heat it acts as a heat
sink and takes the heat away from the
coin starts to evaporate and you get a
lot of gas generated which has to escape
now let's see what happens so the co2
goes directly from being a solid into a
gas so you can see it vaporizing in my
hands now I've got to keep it moving
because it's quite cold and if I leave
it on my hands for too long it'll
actually cause a frost burn if you put
those molecules in a sealed container
like so seal that end up instead of them
just sitting there they'll want to push
out push out against the sides of the
container so we'll put a few pellets of
the dry ice in here and leave it there
and stand back and so because it's being
heated up it's going from solid straight
to a gas and that those gas molecules
are pushing up against the sides of
their film canister and the only weak
point of the canister is the bottom
which is the lid we're going to speed up
that sublimation process by dropping a
piece of this into some water which is
it somewhere near room temperature so
now you can see that the co2 itself is
evaporating to form co2 gas which is
then collecting inside the beaker and
you can see that as this frothy white
gas but when something will happen we
don't know the unpredictability of
science I would just leave the other one
to go now yeah it does that to the kids
as well brilliant
thought I'd take up a light up here you
see a great demonstration of the density
of co2 much more dense than air and you
see as it comes out at the top of the
beaker starts to fall so you can see the
force generated by just putting a few
pellets of carbon dioxide in a tiny
container like this it sounded like a
shot I'd wrung out that's what happens
in a small container like this in
science you know we like to scale things
up so what we're going to do now is put
the dry ice into a large container our
workshop made us a cannon just for dry
ice so as you can see we can actually
put a lot more dry ice in there I'm
going to aim at the fume cupboard there
it's probably the most resistant kit
we've got in here
so let's see how long this will take
bullseye we're just there I think it was