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Nitrogen is an extraordinarily important element
We could make hundreds of youtube videos about nitrogen and still not tell you everything so
Neal and I and Brady have been in the lab we've done what we think is some quite nice
experiments just to give you a flavour of some of the things about nitrogen
So you'll see me trying to smash a banana
You'll see brown gases being generated
sodium azide
Going off in quite a spectacular manner and one or two other things, so it's really fun
But there is some quite a solid chemistry behind it
Liquid nitrogen which boils at minus
196 degrees centigrade is used as a coolant all over the world in laboratories and
industrially. When nitrogen comes out of the container.
It's obviously cold and you can see in the thermal
imaging how the low temperature cools everything around it. It also freezes the water vapour in the atmosphere.
So you get quite nice clouds of what looked like steam but is actually tiny particles of ice.
I used to use it. My shoes cracked through freezing in
liquid nitrogen.
I never tried freezing a banana
So Grady wanted to see the professor trying to smash a banana.
BANG
When you cool things in liquid nitrogen,
fruit for example that contains water the water freezes, so the banana goes absolutely
rigid and then if you hit it with a hammer or something else the ice
shatters and it can make quite a spectacular mess.
The salt that Neal hates chemists use liquid nitrogen first of all because it's safe.
Liquid oxygen would cause or potentially could cause fires, explosions.
You've seen a liquid oxygen and cotton wool going much also easy to obtain
it's a major component of air, it's quite cheap to make. Also it has a convenient temperature of
77 degrees Kelvin (- 196 degrees centigrade), which is a useful temperature,
which freezes most things, most gases, most things that you use in the lab.
Sodium azide is a salt of sodium Na+ and the azide ion N3-
Azide comes from the French name for a nitrogen Asort.
N3- is
potentially a very unstable
anion, if you heat it, it can turn to nitrogen gas. N2
has a very strong bond between the two nitrogen atoms. So it releases a lot of energy
So we tried heating sodium azide
The reaction is quite simple
It goes to nitrogen gas and sodium vapor the sodium immediately reacts with oxygen and water vapor in the atmosphere
so you get a
orange coloured flame from the
reaction of sodium
Sodium azide is one of the components that's used in airbags in cars
The car, if it's crashing, heats a charge of sodium azide
Which is also mixed with some other chemicals
It releases nitrogen gas very quickly and blows up the airbag.
One said advice that looks likely to be compulsory soon is the controversial airbag.
This drawing shows how it works in a crash a small detonator
releases compressed nitrogen from a tube and this inflates the bags concealed in the dash and the steering column.
But I've never seen it heated up neither Neil actually. It's really quite beautiful when you heat it up
Other resides, particularly of heavy metals like Lead, Silver, Mercury are sometimes used in
detonators to set off explosives because if you bang them they decompose very rapidly.
Although nitrogen is very unreactive,
it can be persuaded to react with oxygen and it forms a whole series of different oxides,
compounds that contain nitrogen and oxygen and
their properties are very different. The most stable one is called nitrous oxide sometimes called
laughing gas N2O.
N2O has the property that it dissolves very easily.
In fact, Your brain and mine is largely fat and so N2O
dissolves well in the brain and is very good anesthetic.
It's used in childbirth, but because it dissolves well, in fact, it's also used as a propellant
for instant cream.
Brady and I and Neil has quite a lot of fun squirting our instant cream
Just to show you the nitrous oxide in it
The cream is pressurised with N2O probably with not a very high pressure
atmosphere a few atmospheres when you release it the
dissolved N2O bubbles out, so the liquid cream suddenly goes into a foam ready to go on your cake
(Is it still in the some of the cream when I eat the cream?)
There's probably some N2O left in the cream
but if you wanted to anaesthetise yourself by eating cream,
you would vomit long before you had enough to have any serious effect. The other two oxides of nitrogen
are NO
nitric oxide and NO2
Nitrogen dioxide they're both quite unusual because nitrogen has seven electrons
and oxygen has six so both compounds have unpaired electrons, which gives them slightly unusual properties.
It's quite easy to make NO2
The standard way is just a heat up lead nitrate
Lead nitrate is lead 2+
NO3- (Pb+2NO-3) and when you heat it up you form lead oxide
which is a sort of slightly yellowy orange color and
you make NO2, which is a brown gas and when we heated it up
we got really quite a sort of substantial plume of NO2
NO2 itself can because it has an unpaired electron can dimerise
two of them form
N2O4 and
which is a liquid at room temperature and that we have shown on one of our other videos can be used as an oxidizer
for rockets
For example the lunar module taking off from the moon used N2O4 as the propellant now
It's very volatile it boils at 21 degrees C, so we have to keep it cold and we put it into the reaction chamber
There's another way of making NO2, which is the reaction of
concentrated nitric acid it's important that it's concentrated with metallic copper
and we did this in glassware so that we could collect the gas and see what happens.
So we had a vessel with the acid coming in at the top the reaction taking place and the tube at the side
going into water so we could collect the gas.
You can see that when the acid went in there were clouds brown gas
generated the NO2 before and it went down the tube and there was bubbling as it came out now
we had some quite strange effects, which we hadn't anticipated.
It's one of the exciting things about doing chemistry
demonstrations that sometimes although you understand what's going on
you see effects that surprise you when Neal added a bit more acid the NO2
started dissolving in the acid.
It was already saturated in the acid that was there and
there was a momentary pressure drop which was enough to suck back the water into the vessel and
once the water was sat back the NO2 went on dissolving and dissolving
so the whole lot filled up and the solution went nicely blue with the colour of copper nitrate.
The interesting thing about this reaction is that if you use
dilute or more dilute nitric acid
instead of generating NO2 you
generate NO
Nitric oxide which is not very soluble in water.
So it bubbles out and you can collect it in a inverted test tube.
But NO
reacts very easily with the oxygen in the air to make NO2
so when you take the test tube of NO out of the water air can get in the oxygen in the air,
reacts with the NO and makes the brown NO2 gas. Now the
relevance of all these nitrogen oxides is that in the high temperatures that you get
particularly in diesel engines the nitrogen in the air and the oxygen in the air
can combine to make small amounts of
nitric oxide and NO2 nitrogen dioxide a mixture, which is
conveniently called NOx because x is somewhere between 1 & 2 these nitrogen oxides
in the air are very bad for the air quality
when people breathe them in it can cause all sorts of breathing problems.
And NO2 dissolves in water to make nitric acid so you can get that nitric acid formed and so
NO2 and NO are important environmental pollutants.
(Why does this happen in diesel engines are not petrol?)
Diesel engines operates at a higher temperature than petrol engines.
Which is why they are more fuel efficient. So in terms of carbon dioxide
the emissions for diesel engines are lower than for petrol engines.
You can get more energy out, but in terms of nitrogen oxides, it's not so good.
Thank you for watching.
If you'd like to see more,
Why not check out our playlist with a video for every element on the periodic table or 118 of them.
Or why not check out objectivity a channel full of science treasures
from Isaac Newton's death mask to the human bones found under Benjamin Franklin's house.
I'll put links on the screen and in the video description. Subtitles added by Saurabh Siaag
Subtitles added by Saurabh Siaag