1、Light Tools,Lab 9,Review,Presence of protons: pH Transfer of electrons: redox,New,This week is ESSENTIAL for next weeks lab Next week a lab report will be assigned that is worth a big chunk of your grade,Fire,Why can you see fire? Why do you see colors when some chemicals are flamed? Demonstration:

2、CuS and CaCl Electrons are excited, they move up an energy level then relax back down. The energy difference is released in the form of light,Hydrogen Atom Model,There are only certain levels to which you can excite an electron Only certain photon energies can be absorbed or emitted Distance between

3、 orbitals represents difference in energy An electron cannot be in the middle of energy levels,Hydrogen Atom Model,Only certain photon energies can be absorbed The electron can come back down in one step, or more giving off different energies as photons In fire, the excitable electrons in CuS come b

4、ack down releasing a different energy than the electrons in CaCl did This accounts for the difference in colors,Sunlight,Turns out white light is not all wavelengths of light The atoms in the sun absorb certain wavelengths so that it is not emitted by the sun This is how scientists figured out what

5、the sun was made of,Sunlight,Spectrophotometry,Appendix D Light source of all wavelengths comes out of spectrophotometer The detector tells you how much makes it through Light can not exit by either 1. Being blocked 2. Atoms absorb it and reemit in random directions so that only some makes it out,Sp

6、ectrophotometry,In groups, look at spec (do not turn the machines off at any time) Set wavelength on top to the wavelength the tape says We are going to calibrate the machines Bottom left knob: Set for no light making it out, absorbance=100% (w/o the tube pressing down the detector is blocked from l

7、ight) (abs. is the bottom numbers),Spectrophotometry,Right bottom knob: Set for zero absorbance using tube of water You are going to measure the absorbance of each of the 5 dyes at 6 different wavelengths Use table in appendix i,Spectrophotometry,After this, use graph paper of appendix i to graph wa

8、velength versus absorbance for each dye Before graphing, predict for each dye what wavelengths of light they will absorb,Dye Structures,Dilution,What fraction of dye molecules do you have to have to make the absorbance double? Twice as much (as stated in Behrs Law) How would you build a tube that ab

9、sorbs a as much? Do this, use the dye that absorbs the most at your specs wavelength. Dont dilute the original tube! Use a new one.,Photosynthesis,Picture of photosystems We will be working on photosystem ii Photon hits electron, the electron is excited The electrons are coming from splitting H20 Im

10、portant: The photon does not hit water (this is a common misconception) The splitting of water is what releases O2,Possibilities,Possibilities for the excited electron: 1. It could relax back down and give off a photon as energy 2. Or it could go through the electron transport chain,What does spinac

11、h want?,Protocol on pg. 9-3 Isolate some the spinachs chlorophylls by following protocol Make a prediction: What wavelengths do you think spinach will absorb? Measure its abs. at each wavelength as you did for the dyes and make a chart and then graph it.,UV light,Lastly, before you throw out your sp

12、inach extract, put it under UV light (write down obs. After your graph of spinach extract abs) UV light is way high energy, it is past the violet wavelength so it has a shorter wavelength, this means higher frequency, which means more energy The excited electrons are going to relax back in steps, creating red light. What do you think would happen if you put in a drug that steals e- from the ETC? Would UV light glow longer or shorter? Longer! Because now ALL the e- are now available for excitation, they are no longer tied up in the ETC.,Homework,Due next week: 2 charts and 6 graphs: 1 char