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Fast Reactions - Fireworks.
Fireworks have chemical reactions
that 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 different rates at which the chemicals react causes
air molecules to vibrate
and produce different sounds.
Alternating layers of
fast and slow
reacting chemicals
in the firework produce vibrations
in the air which make a whistle or warbling
sound.
A very fast rate of turning solids into gas
causes
an explosion. A shock wave of sound
travels out through the air producing a
loud bang.
Fireworks
are a safety hazard. A container
for
fireworks would show
the hazard symbol for highly flammable.
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