FIRES COLOURS & FIRES Stage 6 Chemistry Syllabus Chemistry
of Art (Option) Identify Na+, K+, Ca2+, Ba2+, Sr2+, and Cu2+ by
their flame colour Perform first-hand investigations to observe the
flame colour of Na+, K+, Ca2+, Ba2+, Sr2+, and Cu2+ (Demo only this
lesson) Explain the flame colour in terms of electrons releasing
energy as they move to a lower energy level Explain why excited
atoms only emit certain frequencies of radiation Explain what is
meant by n, the principal quantum number Identify that, as
electrons return to lower energy levels, they emit quanta of energy
which humans may detect as a specific colour
Slide 5
WHATRE THOSE COLOURS ? glowing. The colours of all glowing
substances have the same starting point. They come from atoms and
molecules that have been excited to states of energy. Atoms in
burning fireworks and stars have become excited by absorbing energy
as heat; then convert that energy into coloured light which is
emitted. The colours shown by an atom depend on how its electrons
are configured. Thus, by investigating the colours an atoms of an
element emit, we can determine its atomic structure and work out
which element it is.
Slide 6
ACTIVITY 1
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ACTIVITY 2 Metal ions can be identified by the unique colours
of their flames. Specific metal ions are used in fireworks to show
different colours
Slide 8
ACTIVITY 2 Metal ions can be identified by the unique colours
of their flames. Specific metal ions are used in fireworks to show
different colours
Slide 9
Meetal Kumar HOW ARE THESE COLOURS EMITTED AT AN ATOMIC
LEVEL?
Slide 10
ATOMIC EMISSION SPECTRA in the ELECTROMAGNETIC SPECTRUM
Electromagnetic spectrum: range of all wavelengths of
electromagnetic radiation Atomic Emission Spectra: Set of
wavelengths of the electromagnetic spectrum emitted by excited
electrons of an atom
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What happens when white light passes through a prism?
Instructions: 1)Turn on the ray box 2)Place the prism flat on the
paper in front of the ray box so that the beam of light passes
through it 3)Turn off the lights 4)Observe the beam of light as it
enters and exits the prism What do u see?
Slide 12
WHAT HAPPENS WHEN WHITE LIGHT PASSES THROUGH A PRISM? The light
is separated and dispersed into the full visible spectrum
Slide 13
FOR EXAMPLE: Sunlight passes through a raindrop the light is
dispersed into a visible rainbow
Slide 14
QUESTION What happens when we hold a prism in front of light
emitted from these specific burning elements? Would we see the
entire visible spectrum? A: Yes, we would see the entire visible
spectrum B: No, we would see bands of light broken up C: No, we
would see the colours refracting back into its white light form
Answer: B: No, we would see bands of light broken up
Slide 15
For example, Na+ light is broken up into bands within the
spectrum - Notice each element has a unique spectrum that is
emitted, referred to as its Fingerprint and allows us to determine
which element is becoming excited
Slide 16
FIRST LETS LOOK AT THE ELECTRON CONFIGURATION OF AN ATOM
Quantum numbers = energies of electrons in atoms or shells They are
like the address of the electron No two electrons can occupy the
same address N is called Principal energy level It is always a
whole number
Slide 17
QUESTION: If these energy levels or shells are not occupied by
electrons, are the shells still present? Yes or no? Answer: YES!
The energy levels are always present
Slide 18
HOW DO FLAME TESTS WORK
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WHAT CAUSES THE ELECTRON TO BECOME EXCITED? 1) Electron begins
in Ground State (electron in n=1) 2) Energy eg. heat is absorbed by
electron 3) Electron bounces to higher energy level enters Excited
State (eg N=2,3,4) 4) Electron releases Photon (light energy) moves
back down to lower level energy N=1 UV rays ( not visible) N=2
Visible N=3+ - IR rays (not visible)
Slide 20
HOW DO FLAME TESTS WORK
Slide 21
Using all this information allows us to observe colours emitted
from fireworks or outer space for example and determine which
elements are becoming excited and emitting that colour of
light
Slide 22
Pembe Hussain EMISSION SPECTRA
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MARS Pale yellow patches Dark red patches
Slide 24
CHEMICAL COMPOSITION OF MARS Pale yellow/white patches =
hydrogen, helium, sulfur and sodium. Iron oxide and small traces of
calcium Canyons = shadows
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JUPITER Pale grey Orange
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JUPITERS COMPOSITION Hydrogen, helium with ammonium
Phosurphous, sulfur and hydrocarbons
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SUN WHEN IN SPACE Naturally white with slight blue tinge
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SUN WHEN IN SPACE Helium and hydrogen
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COLOUR OF THE SUN WHEN IT IS UP DURING THE DAY
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SUN WHEN IN SPACE Helium and hydrogen No interfering
wavelengths
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SO WHAT ARE WE TALKING ABOUT?
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VISIBLE LIGHT The only electromagnetic waves detectable by
human eyes
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Slide 34
WHAT IS A WAVELENGTH? It is from one bump to another. The
technical term for a bump is a crest
Slide 35
Each colour has its own wavelength that sets it apart so we can
see it
Slide 36
WITHIN THE VISIBLE LIGHT SECTION, WE HAVE A BREAK DOWN OF
COLOURS so that means: Visible light has its own spectrum`
Slide 37
RIDDLE: What does a fingerprint belonging to a human being, and
the electron configuration of an element have in common???
Slide 38
SO: EACH ELEMENT HAS ITS OWN UNIQUE VISIBLE WAVELENGTH AND
COLOUR They are both unique to the individual and element Different
electron configurations Different electrons being excited @
different energy levels (n) different photons released different
wavelengths
Slide 39
QUESTION: Does an element emits only one colour? Yes and no. We
see only one colour but, as electrons travel between different
energy levels, they release different photons and wavelengths. We
just see the most dominant wavelength.
Slide 40
POTASSIUM - K + Flame colour is lilac YET: the potassium
wavelength is a mixture of red @650 nm and blue @475 nm. 4000 A o
5000 6000 7000 An atom actually emits all of the colours, but the
only colour detected by the human eye is that wavelength most
dominant in the emission spectrum
Slide 41
SO. Potassium when heated emits a lilac flame because: 4000 A o
5000 6000 7000 It is the dominant wavelength
Slide 42
EACH EMISSION SPECTRUM IS UNIQUE TO ON PARTICULAR ELEMENT Why?
Because it is like a finger print EMISSION SPECTRUM shows the
electron configuration of a specific atom 4000 A o 5000 6000
7000
Slide 43
APPLICATIONS: Identify different chemicals in a
solution/substance for art restoration and chemical analysis
Fireworks Astronomers use telescopes with detection devices that
are sensitive to wavelengths Determine composition
Slide 44
FLAME TEST COLOURS Sodium, Na Calcium, Ca
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NEXT LESSON: You will perform a first-hand investigation into
observing the flame colours. You will be given unknown solutions
and from this lesson, you will be expected to indentify them.