Transcript No Slide Title

FIREWORK
S
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.
COLOUR
•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 Highenergy, shorter ones are at
the violet end.
•All colours together
produce white light.
LIGHT
Light 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
• Yellows & Oranges use Sodium salts
• Blues & Purples use copper containing
chloride salts, & strontium. These are the most
difficult colours to achieve.
• Greens
use Barium salts
Creating Fireworks
Fireworks are more than a pile of chemicals. They
must have structure.
Fireworks are composed of several different sections:
• Shell-
a hard paper cylinder.
• Fuses: Leader fuse, side fuse , and a series of time
delay fuses.
• Lift charge - propels firework into the sky.
• Stars-
•
the light emitting compounds.
Bursting charge- contains a fuel and a oxidizer.
BOHR'S MODEL
OF THE
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:
Gatorchem
and
Griffinchem
“Colors bursting in air”
by Tim Graham edited by T. Knock
ChemMatters October 1998
Edited and modified February 2000