today we're doing a new experiment new
for
us holy
crap I got
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it the reaction of sodium with water is
terribly well known we've done it lots
of times on our videos you drop a piece
of sodium into water and because sodium
is lighter than water it skits around on
the
surface and reacting liberating hydrogen
and then sometimes the hydrogen catches
fire and in one of our videos exploded
you can see the orange sodium
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flame and a piece of it hit the camera
oh it's on your
camera oh it is too this time we want to
react a small amount of water with an
excess of sodium and the way we've done
it is take a piece of sodium and put it
in the bottom of a beaker and then drop
drops of water from quite high up onto
the block of sodium so one drop after
another
so what happened was that the first few
drops hit the surface and because it's
hard probably ran partly off and a
reaction started round the bottom of the
lamp of
sodium and you can see
Bubbles and the bubbles are probably
Hydro
coming off because the reaction of water
with sodium gives sodium hydroxide and
hydrogen since there isn't very much
water there'll be a strong solution of
sodium hydroxide and that's unlikely to
boiled because the alternative
explanation of that these are bubbles of
steam and then because the reaction
produces
heat it appears that the sodium melted
but because it's quite a small piece it
just stayed as a glob of liquid sitting
on the bottom of the
beaker then when the last drop came down
it very conveniently hit the surface of
the sodium more or less
Square holy
crap I got
it and because water is quite dense it
made a crater as it were a puddle where
it hit the sodium
and then because the water is denser
than sodium it's settled inside the
liquid sodium imagine you have liquid
sodium the melting point is
96° Celsius or Centigrade however you
like to say it and which is very close
to the boiling point of water and of
course it could have been hotter than
96° so when the water goes in it may
well be in an environment that is higher
than its boiling point but because the
water is denser and has momentum it will
go down to the bottom so it's completely
surrounded by hot sodium and the
reaction starts and if you look
carefully first of all the reaction
blows upwards presumably going through
the hole that the water's made going in
and you can see an orange color which is
probably the color of hot sodium vapor a
few frames later on the reaction really
gets going and the pressure of gas
probably hydrogen blows the whole thing
apart because there's much less water
than sodium the liquid that comes out
must be not completely but a large
amount of it will Bey droplets of
metallic sodium and as these droplets go
through the air some of them will react
with the water vapor in the air and some
will react with the oxygen in the air
and there's a lot more oxygen than water
and you can see there one or two pieces
that come off in this direction that are
glowing really very hot and orange it
just demonstrates that when you do an
experiment in a new way you see even
quite a common reaction in a completely
new
light of course to understand precisely
what's going on you'd have to do lots of
different experiments varying the amount
of water varying the temperature of the
sodium perhaps even putting a thermac
couple into the sodium to measure the
temper temperature but doesn't really
matter what does matter is you can see
that even this reaction is more exciting
than we thought as you know sodium is
only the second of the alkaline metals
as you go down the group and we were
lucky enough when we were using the
high-speed camera to also video
potassium rubidium and
cium and in the next few weeks you'll be
able to see all of those and some of
those were even more exciting than
sodium
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