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Chemical Ideas 6.7 Where does colour come from?
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25 questions to see what you’ve 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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7. What colour does the ball look? Explain transmit absorb reflect
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8. What colour does the ball look? Explain. transmit absorb reflect
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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 6.1 Light and the electron.
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Sometimes we use the wave model for light … λ (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 = λν problems…. Work out v: 13. If λ is 3.00 m 14 If λ is 30.0 cm 15. If λ is 3.00 mm Work out λ: 16. If ν is 3.00 x 10 10 Hz c = 3.00x10 8 m s -1
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Sometimes we use the particle model … Packages of energy are called photons Light is a stream of photons E = 6.63 x10 -34 x 4.5 x 10 14 = 3.0 x 10 -19 J Hz h = 6.63 x 10 -34 J Hz -1 Planck constant
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E = hν problems … h = 6.63 x 10-34 J Hz -1 Planck constant 17. If the frequency is 1.089 x 10 6 Hz, what is the energy of each photon? 18. If E = 3.65 x 10 -20 J per photon, what is the frequency (ν) 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. ΔEΔE Electrons absorb energy and move to a higher energy level. The electrons drop back to a lower energy level and emit energy. The frequency of the radiation emitted depends on ΔE.
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20. Red? 21. Blue/green? ?
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5 7 etc 1 2 3 4 6 22. Why no 7 2 8 2 9 2?
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23. What happens to electrons? 1 2 3 4
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Chemical Ideas 6.2 What 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. ΔE 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 … λ (lambda)= wavelength
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11. Wavelength increases, Frequency ? C decreases
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energy wavelength frequency 12.
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c = λ ν c νλ c = speed of light = 3.00 x 10 8 m s -1 λ = wavelength m lambda ν = frequency Hz ( or s -1 ) nu Use m for λ
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C = λν problems…. Work out v: 13. If λ is 3.00 m 14. If λ is 30.0 cm 15. If λ is 3.00 mm Work out λ: 16. If ν is 3.00 x 10 10 Hz c = 3.00x10 8 m s -1
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Sometimes we use the particle model … Packages of energy are called photons Light is a stream of photons E = 6.63 x10 -34 x 4.5 x 10 14 = 3.0 x 10 -19 J Hz h = 6.63 x 10 -34 J Hz -1 Planck constant
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Rearranging again…. E h
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E = hν problems … h = 6.63 x 10-34 J Hz -1 Planck constant 17. If the frequency is 1.089 x 10 6 Hz, what is the energy of each photon? 18. If E = 3.65 x 10 -20 J per photon, what is the frequency (ν) of the radiation?
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19. Black background Coloured lines. emission
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Spectroscopy Sample of hydrogen High voltage Prism
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Electrons can only exist in fixed energy levels. ΔEΔE Electrons absorb energy and move to a higher energy level. The electrons drop back to a lower energy level and emit energy. The frequency of the radiation emitted depends on ΔE.
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20. 3 2 21. 4 2 ?
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5 7 etc 1 2 3 4 6 22. Why no 7 2 8 2 9 2?
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visibleultra violet E increases
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6 1 2 3 4 Balmer 2 E increasing Lyman ? 1 2 3 4 1
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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? 1 2 3 4 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 Vis + UV Rotational transitions Vibrational transitions Microwave I.R.
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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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X2X2 X2*X2*
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e-e- e-e- filter meter photocell cuvette
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concentration absorbance Absorbance α concentration
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