Uploaded by quimicadascoisas on 12.10.2012

Today, in The Chemistry of Things
we will get to know one of the most spectacular shows of chemistry in our lives.
Who isn't amazed by the explosion of colours and shapes
that light up the sky during a fireworks show?
The essential component of fireworks is the "shell"
usually a paper tube filled with gun powder
and small globes of explosive material called "stars".
Each star contains four chemical ingredients:
A combustible material
an oxidizing agent
a metallic compound responsible for the colour
and a binder to keep these compounds together.
All the light, colour and sound result from these chemical compounds.
During an explosion, the oxidizing agent and fuel react violently
releasing intense heat and materials in gaseous phase.
It is the sudden expansion of gaseous materials
that creates a shock wave that reaches our ears
as the sound of the explosion!
And the heat released in this reaction
is responsible for the brightness and colour of fireworks!
The colours of fireworks are obtained essentially by a process called "luminescence "
The heat released in the blast
is absorbed by the atoms of the metals present in the composition of the "star".
By absorbing energy, the atoms in the metals get their electrons "excited"
out of their usual positions!
When once again they return to their more stable positions
the atom releases the excess energy
but now in the form of visible radiation, or coloured light.
The colour of the light varies according to the metal that is used.
Red is normally obtained with strontium salts or lithium
Orange is characteristic of calcium salts such as calcium chloride
Yellow comes from sodium salts
the most commonly used being sodium chloride.
Yes, that's it, kitchen salt.
Green is obtained with barium chloride
while blue is associated with copper chloride.
The properties of these salts make pyrotechnics a demanding chemical science.
It is necessary to ensure the stability of some of these compounds
strictly control the temperature of explosion
and prevent contamination and mixing colours.
Only in this way can we ensure the beauty of chemistry
illuminating the night sky in celebration!
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