the word is exothermic exothermic is
actually a reaction or process that
gives out a lot of thermal energy an
exothermic reaction or process is one
that gives out heat so if you mix the
chemicals very very slowly it all just
gets pleasantly warm if you mix them too
fast there's a big
bang and there are many many many
examples where people have mixed things
too fast and either had a small bang or
blown up their whole Factory so to
illustrate that what I thought is
actually to do a reaction that
demonstrates a truly exothermic process
so rather than doing a reaction that
generates a lot of I don't know color
change uh sound in terms of an explosion
you know there are other videos that
show that really well so this exothermic
process while it's not a spectacular sum
um hopefully you should see the
temperature um increase dramatically the
rate of reaction when you're doing
exothermic reaction is very important
and what is really important is that if
you have a small flask like this one the
heat can get out quite easily because
they're just quite a lot of surface area
but then if you take something really
big much bigger the surface area is
proportionately smaller so the heat
can't get out so easily so when chemists
scale up make things on a larger scale
that's when things can go
wrong it's just like on a cold day if
you're thin you wrap up really warm to
keep out the cold but your really fat
friend is running around in a t-shirt
saying it's too hot and sweating like a
pig because the fat friend surface area
is much smaller compared to the volume
than yours is so what we have here is
something called calcium oxide you can
see it's in an interesting kind of
container not a glass container um and
it says to open it carefully so if I pop
that there exothermic reactions are
quite
safe just feel your body it's warm it's
warm because it's an exothermic reaction
the food that you are eating the oil
from your crisps is reacting with that
oxygen in the air and letting out heat
in a gentle way but if you set fire to
the oil in the kitchen you can burn the
house down because the reaction is going
to higher temperature and so much faster
so calcium oxide looks pretty much like
any other form of calcium salt it's a
white solid so what we'll do is put some
of it in
[Music]
here okay so we've got about half a
beakers worth of calcium oxide there so
approximately about 100 G so the
thermocup at the moment it's at room
temperature and so room temperature is
about 15 and 1 12° C and it's even
though it's inside the calcium oxide the
temperature is about the same as the
fume cupboard in the room so what we're
going to do now is add some distilled
water to the beaker and we'll see what
happens to the thermac
couple so immediately you're
seeing the increase in temperature so
it's gone from 15 shot all the way up
now to 45 and it's still going strong
when a chemical reaction
occurs you have to start the reaction to
break bonds between
atoms then they react and they make new
bonds and you get some energy back if
the energy you get back is more than the
energy you put in it gets hotter so the
reaction goes faster it releases more
energy and it runs away it goes faster
and faster and
faster but but if on the other hand you
are breaking strong bonds and making
weak
ones less energy comes out than you put
in and you have to keep on heating it or
the reaction just stops within seconds
it's gone from 15 and half de C to over
100 so with this Beaker I'm definitely
not going to touch it because it's going
to be really hot so the this reaction is
known as the the SL laking of quick lime
so it's calcium oxide and water
producing calcium hydroxide