Chemical Ideas 6'7

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Chemical Ideas 6.7

• Where does colour come from?

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25 questions to see what youve remembered.
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More about the colour we see .. Key stage 3 stuff.
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1. What colour is the light reaching my eye?
Explain.
Red filter
transmit absorb reflect
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2. What colour is the light reaching my eye?
Explain.
Blue filter
transmit absorb reflect
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3. What colour is the light reaching my eye?
Explain.
Colourless glass
transmit absorb reflect
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4. What colour does the ball look? Explain.
transmit absorb reflect
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5. What colour does the ball look? Explain.
transmit absorb reflect
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6. What colour does the ball look? Explain.
transmit absorb reflect
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transmit absorb reflect
7. What colour does the ball look? Explain
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transmit absorb reflect
8. What colour does the ball look? Explain.
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9. The rays are

• A. Refracted
• B. Reflected
• C. Dispersed
• D. Converged

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10. Name the 3 primary colours of light
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Chemical Ideas 6.1Light and the electron.
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Sometimes we use the wave model for light

• ? (lambda) wavelength

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11. Wavelength increases, Frequency ?
C
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12. Sketch the e.m.s. and use arrows to mark

• Increasing energy
• Increasing wavelength
• Increasing frequency

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C ?? problems.
c 3.00x108 m s-1

• Work out v
• 13. If ? is 3.00 m
• 14 If ? is 30.0 cm
• 15. If ? is 3.00 mm
• Work out ?
• 16. If ? is 3.00 x 1010 Hz

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Sometimes we use the particle model
Hz
h 6.63 x 10-34 J Hz -1 Planck constant

• Packages of energy are called photons
• Light is a stream of photons
• E 6.63 x10-34 x 4.5 x 1014 3.0 x 10-19 J

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E h? problems

• h 6.63 x 10-34 J Hz -1
• Planck constant

17. If the frequency is 1.089 x 106 Hz, what is
the energy of each photon? 18. If E 3.65 x
10-20 J per photon, what is the frequency (?) of
the radiation?
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19. Absorption or emission Spectrum of hydrogen?

• Black background
• Coloured lines.

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Spectroscopy

• Sample of hydrogen
• High voltage

• Prism

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• Electrons can only exist in fixed energy levels.

• Electrons absorb energy and move to a higher
  energy level.

?E

• The electrons drop back to a lower energy level
  and emit energy.

• The frequency of the radiation emitted depends on
  ?E.

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20. Red?
21. Blue/green?
?
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• 22. Why no
• 7 ? 2
• 8 ? 2
• 9 ? 2?

7 etc
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23. What happens to electrons?
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Chemical Ideas 6.2What happens when radiation
interacts with matter?
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Molecules are made of more than one atom but they
still have electrons.

• Electronic transitions

Vis UV
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24. Molecules move ! How?
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25.There are vibrational energy levels as well as
electronic energy level . ?E in which region?
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The answers
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1. What colour is the light reaching my eye?
Explain.
Red filter
Red
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2. What colour is the light reaching my eye?
Explain.
Blue filter
Blue
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3. What colour is the light reaching my eye?
Explain.
Colourless glass
White
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4. What colour does the ball look? Explain.
Red
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5. What colour does the ball look? Explain.
Black
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6. What colour does the ball look? Explain.
White
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7.What colour does the ball look? Explain.
Red
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8. What colour does the ball look? Explain.
Black
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9. The rays are

• A. Refracted
• B. Reflected
• C. Dispersed
• D. Converged

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10. Name the 3 primary colours of light
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Sometimes we use the wave model for light

• ? (lambda) wavelength

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11. Wavelength increases, Frequency ?
decreases
C
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12.
energy
wavelength
frequency
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c ? ?
? wavelength m lambda
c speed of light 3.00 x 108 m s-1
? frequency Hz ( or s-1 ) nu
Use m for ?
c
?
?
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C ?? problems.
c 3.00x108 m s-1

• Work out v
• 13. If ? is 3.00 m
• 14. If ? is 30.0 cm
• 15. If ? is 3.00 mm
• Work out ?
• 16. If ? is 3.00 x 1010 Hz

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Sometimes we use the particle model
Hz
h 6.63 x 10-34 J Hz -1 Planck constant

• Packages of energy are called photons
• Light is a stream of photons
• E 6.63 x10-34 x 4.5 x 1014 3.0 x 10-19 J

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Rearranging again.
E
h
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E h? problems

• h 6.63 x 10-34 J Hz -1
• Planck constant

17. If the frequency is 1.089 x 106 Hz, what is
the energy of each photon? 18. If E 3.65 x
10-20 J per photon, what is the frequency (?) of
the radiation?
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19.
emission

• Black background
• Coloured lines.

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Spectroscopy

• Sample of hydrogen
• High voltage

• Prism

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• Electrons can only exist in fixed energy levels.

• Electrons absorb energy and move to a higher
  energy level.

?E

• The electrons drop back to a lower energy level
  and emit energy.

• The frequency of the radiation emitted depends on
  ?E.

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20. 3 ? 2
21. 4 ? 2
?
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• 22. Why no
• 7 ? 2
• 8 ? 2
• 9 ? 2?

7 etc
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visible
ultra violet
E increases
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E increasing
Balmer ? 2
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Lyman ? ?
6
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Absorption Spectrum of hydrogen.

• Continuous spectrum
• Black lines.

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How do the 2 compare?
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23.What happens to electrons?

• Electrons absorb energy
• Electrons are excited
• Electrons move to higher energy level
• E h v

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Molecules are made of more than one atom but they
still have electrons.

• Electronic transitions

Vis UV
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24. Molecules move ! How?
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25. There are vibrational energy levels as well
as electronic energy level ..
I.R.
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• Electronic transitions

• Rotational transitions

Vis UV
Microwave
I.R.

• Vibrational transitions

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Chemical Ideas 6.7 Where does colour come from?
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• Absorb
• Transmits
• Complementary

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• Absorb
• Transmits
• Complementary

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• Absorb
• Transmits
• Complementary

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X2
X2
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photocell
filter
e-
e-
meter
cuvette
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Absorbance a concentration