Brady thought that tin was a really
boring element but we've changed his
mind showing him that it does more than
it says on the tin what we can show you
is how tin melts how you can join wires
on the battlefield while you're being
fired at by the enemy how you can stop
things growing on the bottom of ships
and also give you a few hints about a
first-year chemistry course if you come
here to the University tin is in group
14 the same group as carbon so it is
below germanium and above LED it was
really valuable in prehistoric times
because it was found that when you mix
it with copper you could make bronze and
bronze melts at a lower temperature than
copper so it's easier to make weapons
and the weapons were harder tin is found
in a variety of minerals they're love
sources of it in China in Malaysia and
also in Cornwall in the West of England
after the ore has been crushed and
washed the tin oxide is dried and
samples tested for quality and good
stomp orchard Year with 140 pounds of
tin from a ton of ore there are still
many abandoned tin mines in Cornwall
they're quite dangerous when you walk
across the Moors there are open shafts
which if you're not looking where you're
going you can fall down eventually
Cornwall do provide a third of all the
tin required by this country we have
been trying to look at tin beginning
with the metal
one of the interesting things about tin
is that it melts are quite a low
temperature so if you heat it up it
melts around 230 degrees centigrade so
even with a gas torch you can melt it
quite easily in the glass test tube this
low melting point is very useful for a
whole series of applications
particularly for so-called solder that
is joining things electrically this is
solder it is the metal which is used to
make electrical connections in this case
on a very old computer memory board now
to make joints like this requires
precise tools and it's a bit boring but
what we want to show you is how people
joined wires together on the battlefield
for example in the Second World War
you've got to imagine you're on the
battlefield people are shooting at you
you need to put down the telephone wires
so you can talk to the groups on either
side of you and the last thing you want
to do is to get out to soldiering iron
and wait for it to heat up and so on I
remembered that I had some self
soldiering joints which I got when I was
an army cadet when it was about 15
there's a copper tube with some solder
inside and some material that burns so
that you can light it like a match so
you take the two bits of electrical wire
you want to join post one piece of wire
in each end and then you light it the
solder is inside I've had these 56 years
and they weren't new when they got them
so they probably come from the Second
World War
they're probably surplus I thought they
would work Neil was a bit dubious as
usual I was right
so Neal set fire to the red part which
is some sort of igniting mixture and it
flared up quite quickly and then you can
see the whole tube gets very hot now of
course you can't see the solder because
that's inside there as it gets hot the
solder melts and runs round the wires
and then as it cools down it solidifies
fixing the wires into the short piece of
copper tube on one occasion we did it
more than once you could see the solder
coming out just on one side
[Music]
just to showed that the solder was in
there I persuaded Neil and our new
assistant Connor who's joining our team
to heat one of these pieces vertically
so that when they sold the melt it will
drop out the bottom
just to show you that it got hot we put
the thermocouple which measures
temperature into the top so you can see
the temperature going up and you can see
the solder running out
[Music]
so we were really quite excited then we
thought tin is in the same group as
carbon-carbon burns so perhaps tin will
burn well in a bunsen we found some very
nice finely powdered tin Neill started
sprinkling the tin into the flame of the
Bunsen burner and it was really
beautiful you could see all sorts of
swirling flames and when the tin went
into the flame you got quite a bright
coloured light now there's some argument
whether it was violet or lilac and that
there was a touch of green as well which
I think came off your spatula it was
really much more beautiful than any of
us had expected and then Neil had a
really good idea he fed the powder into
the air hole of the Bunsen burner the
stream of gas then blew the powder up
into the flame and that looked even
better
so we take two really good experiments
demonstrations and so we felt really
ready to go for a third now ten is very
well-known of having two different forms
of the metal one of them is shiny and
looks just like any other metal the
other one is meant to be a sort of
brownish color and crumbles away this
transition between the two happens at
low temperature and I'd seen the
terrific time-lapse video on YouTube
where you can see a block of metallic
tin gradually crumbling away as this
so-called tin pest spreads across so we
thought we will try the same but perhaps
we were not quite so patient
[Music]
so first of all I had the dice tin
soldier and we tried dunking the soldier
in liquid nitrogen
[Music]
he came out looking much the same but we
hoped it had transformed inside so Neil
thumped it with a hammer that was
successful it shattered the bits but
there was absolutely no evidence that
the metal had changed
it was just Neil's power that smashed it
so we then tried a different experiment
melting the tin and pouring the molten
tin the liquid tin into liquid nitrogen
the thinking here was that if we froze
the liquid quickly it would go into the
unstable form directly without going
through the metallic one so it was
really quite spectacular when it went in
there were great plumes of vapor vapor
water vapor as the nitrogen evaporated
and when we took it out it was a rather
beautiful shape of long piece of tin
where it was the shape of the test tube
so it looked byte artistic but he didn't
demonstrate what we wanted we thought
perhaps we were being a bit impatient so
we left it in liquid nitrogen overnight
one a piece of string in case it
crumbled away and sadly when we took it
out the next day still hadn't
transformed
[Music]
the ones we've been completely
unsuccessful I think that when we did
we've done it at too low a temperature
you probably need it a bit below
freezing point of water so minus 10
minus 20 degrees centigrade and when
it's really cold liquid nitrogen
temperature the atoms don't have enough
thermal energy to rearrange if we left
it in liquid nitrogen for a couple of
years perhaps something would happen so
as well as bronze there's a very
well-known alloy of tin computer
originally it was tin and lead it's no
tin with other metals is particularly
famous in Malaysia you get many
souvenirs and when I was in Malaysia I
was given this plate made that pewter
and the reason why people liked it is
because you can melt it quite easily and
make it into elaborate shapes like the
pattern on this plate now we really
haven't talked about the chemistry yet
tin is in the same group as carbon so it
has four electrons in the outer shell
but unlike carbon it can either use two
of these electrons or four of these
electrons for bonding when it uses two
electrons it forms
say tin dichloride stannous chloride
which is a salt rather like sodium
chloride so it dissolves in water makes
a slightly cloudy mixture if you put too
much in but it dissolves but it will not
dissolve in organic solvents like
cyclohexane on the other hand if you use
four electrons you can make compounds
like tin tetra iodide which is one of
the compounds our students make in the
first year lab and we had two samples
made by students and you can see the
colors are a bit different because one
made a pure sample than the other the
two
tetra iodide is like an organic compound
if you put this one in water the tin
iodine bonds react with the water so you
get hydrogen iodide which you can't see
and you get a precipitate of tin oxide
which is white if you put it in an
organic solvent it dissolves so you get
a nice yellow solution I won't say any
more
or you might cheat when you're a student
here tin oxides are important in screens
on smart phones and similar things
because this display consists of a
material which is sandwiched between two
electrodes and obviously the electrode
through which you're looking has to be
transparent and indium tin oxide that's
a mixed oxide of indium and tin is
trettel ectric lis conducting but is
transparent so indium tin oxide is a key
component of most smartphones and other
displays so if you're watching this
you're probably watching it through a
thin film of indium tin oxide the final
application of tin that I want to tell
you about involves chips
this is a wooden ship but it's the only
one I could find when the ship is made
obviously the bottom of the ship is
absolutely clean but as it sails around
the Seas various marine organisms
mussels barnacles and so on fix
themselves to the bottom of the ship and
start growing so eventually the bottom
of the ship looks rather like my hair
with covered in these marine organisms
and this greatly slows down the ship it
doesn't go through the water so easily
so for centuries people have tried
different sorts of coating on the bottom
of ships for so called antifouling to
stop organisms growing on them a very
successful method is involved using
organo tin compounds usually derivatives
of tributyl tin these are very effective
in preventing growth on the bottom ship
the problem is that the tin can leech
dissolve off the bottom of the ship and
particularly near ports because there
are a lot of ships there and they spend
quite a lot of the time there and when
the tin comes out of course it stops the
organisms the barnacles fixing onto
rocks and all sorts of things so in
recent years there's been quite a strong
movement to stop using tin in
antifouling paints and to use clever
paint chemistry to make the bottom so
smooth that nothing can stick to it
there you go
and to think I thought a video about 10
would be boring as you probably know
we've made videos about all the elements
on the periodic table but like the one
you just watch then we're redoing them
making them bigger and better if you'd
like to support us help us make those
new videos like the people whose names
you see on the screen at the moment you
can back us on patreon go to
patreon.com/scishow with them this video
about the professor's tire collection
you haven't lived until you've seen a
video about the professor's tire
collection anyway there are links down
in the video description thank you so
much for watching and we'll be back soon