Okay weíre going to be looking today at copper. This is something looking back at the old
video, itís a short video and there isnít any experimentation in it so I thought weíd
do something a bit practical.
Copper is an element which people are very familiar with because itís such a characteristic
coloured metal, sort of reddish colour, though it gets darker when oxide forms. But itís
quite a soft metal and you can cut it quite easily if you have a cutter like this which
has steel blades, it will just dig into the metal and it should just cut off. When you
cut the metal you get this very nice, shiny, fresh surface coloured just like copper.
This is a ball of copper, copper metal. As you might imagine itís a ball of metal so
therefore it is quite dense and heavy. I mean itís not as dense as, I think Steve told
me this morning, that if we had a ball this size of plutonium he told me it would weigh
about a kilo and a half so he thought. So itís not quite as heavy as that but still
itís pretty heavy and dense.
So this is a very, very nice sample of very fine copper wire. So the copper wire here
is, what width is this? This isÖ phew! Point zero, Iím not even going toÖthatís just
too small, so itís point one of a millimetre.
So inside the beaker weíve got a solution called sodium potassium tartrate, so no copper
in there at the moment. Weíre going to introduce that through this. This is a solution of copper
sulphate.
Copper is very popular for architectural use because if you put it on the roofs of buildings
it then reacts, particularly with carbon dioxide in the air, to give a very nice green colour.
First of all though we need to heat this to about 50∞C, and to the sodium potassium
tartrate we need to add some very weak, hydrogen peroxide so this is only 3% hydrogen peroxide,
so in it goes. We need to make sure they mix together which is why thereís a stirring
bar at the bottom there stirring away. Okay so thatís stirring nicely, so as I said sodium
potassium tartrate and hydrogen peroxide and we need to add only one mill so thatís 1cm3
of the copper sulphate.
The copper wire here is very, very high grade, this is grade one copper wire and itís point
one of a millimetre in diameter and you can see the wonderful copperas lustre coming off
the side there.
What do you mean by grade one copper?
So this is very high purity, this is like 99.99% copper, used for electronics fabrications
and high quality research samples.
Itís also used for electrical wiring, in fact itís used so much that in a country
like the UK each person has about 175 kilos of copper associated with each person, in
the piping, the wiring and so on. The problem is that in many other countries, for example
in China, people have very much less copper associated with them, there isnít so much
electrical wiring in rural parts of China. And if everybody in China had the same amount
of copper associated with them as those in England or America or Canada there wouldnít
be enough copper in all the known deposits around the world.
Copper is actually necessary for life, plants and animals use copper. But actually you can
have a disease called Wilsonís disease which basically your body canít metabolise copper
properly, itís actually an inherited disease.
Ready? Whatís going on there is itís producing a lot of gas so itís reacting to form a complex.
And itís going from the potassium tartrate complex there to well, its producing carbon
dioxide and oxygen, mainly oxygen gas is being produced which is why youíre seeing the fizzing.
And itís become copper oxide, cuprous oxide actually.
Copper is found as a metal lying around in various places in the world. I believe the
name came from the island of Cyprus in the middle of the Mediterranean, but copper has
always been know even in pre-historic times people found small amounts of copper. But
as we use more and more copper people have had to dig deeper and deeper mines. The mine
in Chile where those very brave miners were entombed for more than two months and then
rescued was a copper mine. And to get the metal that we need weíre going to have to
go deeper and deeper and deeper into the earth.
So what weíve got in there now is cuprous oxide itís copper 1 oxide. And itís actually
gone from what was a kind of clear see-through, all right itís got a colour on it, but see-through
solution to something thatís very cloudy. So what weíve got there is a precipitate
of copper oxide.
Copper is very good because it has very high thermal and electrical conductivity. What
that means is that heat flows through it very well and also electricity. If you make wires
for electrical transmission out of copper, when the electricity goes through them you
get very much less heating than say if you made the wires out of iron, and all this heating
is of course lost energy. Youíd do even better if you made the wires out of silver, but silver
is too expensive.
OK. So letís see if we can change this reaction back. So at the moment it started out as being
about 50∞C and itís shot up to about 63∞C, I imagine it was even hotter than that when
it originally changed colour. So weíll see if we can take it back, Iíll put that back
in.
I actually bought this from the British Geological Survey which is just down the road from here,
I think it is in Keyworth I think. And I just saw this and it was a Christmas present from
my husband and I picked it out. I just think itís really cool actually.
What did your husband think of getting that as a Christmas present?
He knows what Iím like! So he buys these things for me he knows Iím a bit of a magpie,
I like to collect shiny things, and pretty things, thatís my copper.
So the colour is gradually changing, itís gone from orange and now kind of a murky yellow.
You can see itís kind of green now. And again a gradual change, it wasnít a sudden spontaneous
straight back to being blue and see-through, you know clear. Now weíve got back to that
clear solution. And again you can see on the stirrer bar all the bubbles of the oxygen,
little bit of C02 forming on that.
Most organisms, you and me, use iron in our blood to transport oxygen, thatís what makes
our blood red. But in some sorts of crustaceans, crabs and lobsters, theyíre different they
use copper. They use a compound called hemocyanin, itís a blue compound of copper. Cyanine is
some classical word for blue. So they really have blue blood. And these hemocyanin use
two atoms of copper in each molecule to transport the oxygen around the body of the crab or
lobster. But itís not nearly as good as haemoglobin, so if you start running after a crab or lobster
it quickly gets tired compared to running after a rabbit or something like that, which
can keep going faster than you can.