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Fast Reactions - Fireworks.
Fireworks
have chemical reactions
which are fast and highly
exothermic.
The reaction is started by putting in heat energy (you
light the firework).
Some colours in fireworks
come from transition
metal compounds.
These can be made from neutralisation reactions.
Some colours in fireworks come from other metal compounds.
Magnesium can
be used to make a brilliant white flame.
Phosphorous compounds can make
fireworks glow brightly.
The solid chemicals in fireworks turn into
large amounts of gas very quickly during the reaction.
The gas has a much bigger volume than the solid chemicals
and this rapid expansion is used in two
ways.
Fireworks
on the ground use the
expansion of gas
to send flames and showers of
coloured sparks into the air.
Some fireworks (for example rockets) use the
expansion of gas
to send the whole firework into the air
where it then explodes
into
showers of coloured sparks. The
expanding gas coming out
of the bottom of the firework pushes it upwards into the air.
Fireworks use sound as well as colour for their display.
The rate at which the chemicals react can produce different sounds.
If the rate of turning solids into gas is a
very fast explosion
then a shock wave of sound travels
through the air producing a
loud bang.
Alternating layers of
fast and slow
reacting chemicals produce vibrations
in the air which make a whistle or warbling
sound.
Fireworks
are a safety hazard. A container
for fireworks
would show
the hazard symbol for highly flammable.
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