2. Unit 6 Light

3. Quantum Theory Max Planck (1900) –Observed - emission of light from hot objects –Concluded - energy is emitted in small, specific amounts (quanta) –Quantum - minimum amount of energy change Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Max Planck

4. Light Particles –photons (discrete bundles of energy) Light is emitted when electrons return to ground state from an excited state Waves –Frequency, wavelength Wave-Particle duality

5. Formation of Light Nucleus e e Lithium Atom + Ground State e e Excited State e Electron Returns to Ground State Light is given off e Ion is formed Li  e + Li 1+ hv n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 Nucleus

6. An Excited Lithium Atom Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 326 Photon of red light emitted Li atom in lower energy state Excited Li atom Energy

7. Heisenberg Uncertainty Principle It is impossible to simultaneously know the exact velocity and position of any object. In order to detect any object’s position (either by eye or with a machine), it has to be struck by light. To see an object, it has to be struck by visible light. For night-vision goggles, it has to be struck by IR light. As soon as it is struck by photons, the e - move, thereby changing its position and velocity. This hardly matters for large objects, but it does for atoms & e -.

8. Electromagnetic Spectrum Light is a form of energy. Energy travels in waves. Waves have two components. Wavelength (distance from peak to peak or trough to trough) Amplitude (distance from center of wave to peak)

10. Visible Spectrum of Light PRISM Slit Ray of White Light Waves 1 / 33,000 ” long Waves 1 / 70,000 ” long R ed O range Y ellow G reen B lue I ndigo V iolet

11. The Electromagnetic Spectrum AM radio Short wave radio Television FM radio Radar Microwave Radio Waves Gamma Rays X- Raysinfrared Increasing photon energy Increasing frequency Decreasing wavelength Red Orange Yellow Green Blue Indigo Violet UV Rays VisibleLightVisibleLight R O Y G B I V HIGHENERGYHIGHENERGY LOWENERGYLOWENERGY

12. Electromagnetic Spectrum Waves can have different wavelengths Wavelength Energy Frequency

13. Flame Emission Spectra Photographs of flame tests of burning wooden splints soaked in different salts. methane gas wooden splintstrontium ioncopper ionsodium ion calcium ion

14. Fireworks

15. Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

16. Common chemicals used in the manufacture of fireworks Ammonium perchlorate aluminumBlue flame: copper carbonate, copper sulfate, or copper oxide Barium chlorate antimony sulfideRed flame: strontium nitrate or strontium carbonate Barium nitrate charcoal White flame: magnesium or aluminum Potassium chlorate magnesiumYellow flame: sodium oxalate or cryolite (Na 3 AlF 6 ) Potassium nitrate sulfurGreen flame: barium nitrate or barium chlorate Potassium perchlorate titaniumWhite smoke: potassium nitrate plus sulfur Strontium nitrateColored smoke: potassium chlorate and sulfur, plus organic dye Whistling noise: potassium benzoate or sodium salicylate White sparks: aluminum, magnesium, or titanium Gold sparks: iron filings or charcoal Almost any combination of an oxidizer and a fuel may be used along with the compounds needed to produce a desired special effect. Oxidizers Fuels (Reductants) Special Effects Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.