so Halloween in this time of year in
October is a time when people often use
candles and
so we have here a nice Halloween candle
which we can
light and I've always been taught to do
experiments in duplicates so I have
another candle here as
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well and the chemistry of candles is is
really very
interesting it's um in fact the very
famous scientist Michael Faraday wrote a
whole book called The Chemical history
of the candle here's a j Japanese
version of the same book bits smaller
but just the same we take the um fuel
which is the wax which is a compound
that is a long chain of ch2 groups
that's one carbon and two hydrogen
wax melts to make a
liquid and the liquid then is drawn up
along the wick which is just a simple
piece of um like a piece of string and
then it burns and there's an awful lot
of energy stored in a molecules of wax
there's much more energy in a molecule
of wax than there is in a molecule of
TNT when the wax Burns you can imag
imagine that there's this material
burning with oxygen outside here and in
the middle of the flame there isn't so
much oxygen because it has to get into
the
middle
and so the color of the flame actually
comes from very hot particles of
carbon you can see this quite easily if
you take a spoon and put it in the flame
of a
candle just like
this you can see then you get a very
nice coating of here of the black carbon
particles we seeing light for just the
same reason that if you heat up a piece
of wow as it gets hotter and hotter the
vibrations of the atoms give out
light and so it's just because the
particles of carbon are literally red
hot now there are two other things which
are really quite exciting about the
candle one is that because the wick is
right in the middle of the flame it's
kept away from the oxygen and in the old
days the wick grew longer and longer and
longer and candles got more more and
more smoke from them so now what happens
is that there's a very clever piece of
design that the candle wick is made so
that it is rather like a sheet of paper
and as it gets longer the end bends over
so you can see over here that the FL
candle wick has bent right over so the
end of it is right at the edge of the
flame and so as it is at the edge of the
flame it just burns off so as the flame
candle goes down it automatically trims
the end of its
candle that's quite so so in the 18th
century before this was invented people
had special scissors and every time
every
few minutes perhaps every quarter of an
hour you had to trim your candle to stop
it smoking but now it does it
automatically
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now the other thing which is quite
exciting about candles is what happens
when you make them go out so when I blow
it out look carefully and you'll see
what looks like
smoke so this actually isn't smoke but
it is tiny particles of wax which
because the vapor of the wax has
suddenly getting colder it Sol
solidifies and you get these tiny tiny
particles much smaller than a millionth
of a meter formed so now I'm going to
try and do it again but this time when
the wax is streaming up I'm going to
show you its Wax By lighting it with a
match so are you ready watch
carefully so as I held them I was
holding the match about here and you can
see that the FL the um Wick is here and
so the flame jumped all that distance to
start lighting the candle again and it
made that jump because it went down the
stream of wax that was floating up from
the wick and of course the wick was
still hot because it's been burning so
once it got to the wick it didn't need
very much heat to start it
off very good thank
you okay yeah fine
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