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HISTORY

• Writings from 850 AD show that the Chinese used black powder to create “fireworks”.

• People learned to encase black powder, making flares and missiles that would frighten invaders.

• By the 12th century fireworks had become a part of religious ceremonies and many celebrations.

PYROTECHNICS(the art and science of artificial fire)

• Fireworks must contain: -an oxidizer which provides oxygen for combustion

-a fuel that acts as reducing agent• Oxidizers are electron deficient and so react

with the fuel to increase their stability. This is an exothermic process; the energy that is released offers a spectacular show.

COLOURCOLOUR•The colour of light we see depends upon the wavelengths of the electromagnetic radiation.•The visible spectrum contains red, orange, yellow, green, blue, and violet. Low-energy, longer wavelengths are at the red end of the spectrum and High-energy, shorter ones are at the violet end.•All colours together produce white light.

LIGHTLIGHTLight is emitted by:

• Incandescence

• Atomic Emissions

• Molecular Emissions

Incandescence

This kind of light is also known as white light .

• Incandescent light is created when solid materials are heated to high temperatures, thus creating light.

• Explosions with gold or white colours often result from reacting metal shavings in a high temperature

environment.

Atomic & Molecular emissions

These emissions create brilliant colour bursts.

•Atomic Emissions: When light is emitted by atoms of an element in the gaseous phase each element has unique colour.

•The high temperature environment that is generated when a shell explodes causes electrons to jump to higher energy levels in atoms.

•When these “excited” electrons fall back to a lower energy level they emit light of particular colours or wavelengths.

•Molecular Emissions: can produce similar effects but are results of molecules instead of elements.

Creating Colour

In order to achieve these different colours, Pyrotechnicians must add different elements (salts)

to the fireworks.

• Reds use Strontium and Lithium salts

• Greens use Barium salts

• Yellows & Oranges use Sodium salts• Blues & Purples use copper containing

chloride salts, & strontium. These are the most difficult colours to achieve.

Creating FireworksCreating FireworksFireworks are more than a pile of chemicals. They must have structure.

Fireworks are composed of several different sections: • Shell- a hard paper cylinder.Shell- a hard paper cylinder.

• Fuses: Leader fuse, side fuse , and a series of time Fuses: Leader fuse, side fuse , and a series of time delay fuses. delay fuses.

• Lift charge - propels firework into the sky.Lift charge - propels firework into the sky.

• Stars- the light emitting compounds. Stars- the light emitting compounds. • Bursting charge- contains a fuel and a oxidizer.Bursting charge- contains a fuel and a oxidizer.

BOHR'S MODEL BOHR'S MODEL OF THE OF THE

HYDROGEN ATOM:HYDROGEN ATOM:

•According to Bohr's theory, the electron can orbit the proton (nucleus) only in certain "ENERGYLEVELS" or principal quantum levels, numbered n=1, n=2, n=3, etc., with n=1 being the normal or GROUND STATE level for the electron.

• When the electron is excited up to the n=2 or higher level, a photon of light is absorbed, giving an absorption spectrum. Since the energy levels have a definite spacing, this results in photons of a specific colour or wavelength being absorbed.

•When the electron "falls" from a higher to a lower level, light is emitted, giving an emission spectrum.

The BALMER SERIES is the visible spectrum series of emission lines for the Hydrogen atom. These lines are the result of transitions from: [n = 3 to shell 2] red, [n = 4 to n = 2] blue green, [n = 5 to n = 2] blue, [n = 6 to n = 2] violet, all ending in n = 2 energy level. These transitions can be modelled as follows.

Visible Spectrum

• Brilliant colours that are seen during a show are from:• Incandesce: Light is created when solid materials are heated

to high temperatures, thus creating light

• Atomic: When light is emitted by atoms of an element in the gaseous phase each element has unique colour. – The high temperature environment that is generated when a shell

explodes causes electrons to jump to higher energy levels in atoms.

– When these “excited” electrons fall back to a lower energy level they emit light of particular colours or wavelengths.

• Molecular: Molecules can produce similar effects but are results from molecules of compounds instead of elements.

Presented By: GatorchemGatorchem

and and

GriffinchemGriffinchem

““Colors bursting in air” Colors bursting in air”

by Tim Graham edited by T. Knockby Tim Graham edited by T. Knock

ChemMattersChemMatters October 1998October 1998

Edited and modified February 2000Edited and modified February 2000