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How?. Why?. Light Tools. Building and confirming tools for inquiry. Think with me. Why do you see colors when some chemicals are flamed? Why do different chemicals => different colors? Assertion I : (proposed model): unlike planets, electrons are only allowed discrete energies*
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How? Why? Light Tools • Building and confirming tools for inquiry
Think with me • Why do you see colors when some chemicals are flamed? • Why do different chemicals => different colors? • Assertion I: (proposed model): unlike planets, electrons are only allowed discrete energies* • Assertion II: Energies that don’t take an electron to an allowed place are ignored by it *If the earth should stop revolving, Spinning slow enough to die... --IF, David Gates (Bread)
Hydrogen Atom Simulator (Dan Damelin) • http://chemsite.lsrhs.net/FlashMedia/html/flashEMR.htm • Also in Further Explorations (on course website) • Predict: what happens to an arbitrary-energy photon? (on the slide bar labled ‘Photon Energy’ these are 10, 11, 12 & 13) • Predict: what happens to one that matches a difference between current & potential orbital? ((on the slide bar labled ‘Photon Energy’ these are 10.20, 12.09, etc.) Set ‘pause mode’ to on
What is ‘color’ • Is there a difference between your shirt and a neon light?
How are these different? • Using a thermometer to test temperature • pointing stick at sky, say magic words, wait for rain • using ‘pH paper’ to count ‘protons’ • using the Ba(OH)2‘test for’ carbon dioxide • counting geigs with a Geiger counter • believing in ‘global climate change’ Any sufficiently advanced technology is indistinguishable from magic. --Arthur C. Clarke
Capturing CO2 H2O + CO2-> H2CO3 H2CO3-> HCO3–-> CO32– CO32– + Ba2+->BaCO3 (white ppt.)
Rankings • Empirical--you saw it, touched it, etc. • Reasoned argument from documented/identified assumptions & previous knowledge • Repeatedly established by others • Never: assertions by authority regardless of the nature (or volume) of that authority
Set for infinite absorbance (blocked path) Set wavelength Set zero absorbance Driving Ms. Spec **Appendix D also reviews how to use this Spec
SEE for yourself! • We’ll have tubes with chalk or filter paper; drop these in the specs • Look at the beam (far red may be hard to see) • slowly and carefully move the wavelength selector • Look again • Reset spec to wavelength indicated by tape on spec
Evaluating your expectations • Graph paper pp. J-13 to 20 • Predict: how will a blue liquid absorb? A green one?
To your specs! • Tubes in the rack • Find the absorbance of each color at • each wavelength (record – Appendix I has tables) • MOVE your body to the next wavelength (the next spec) • Protocol for chlorophyll on 11-3
Data This should take 15’.
Graphing • Create a graph, table for HW • See rubric!!!
FYI: Dye Structures Napthol Green FDC Yellow5 Yellow Crystal Violet FDC Blue1 FDC Red 3
The Joy of Dilution • What fraction of molecules would you have to remove for there to be 1/2 as many collisions between beam & dye? • OK, build a solution with 1/4 absorbance of stock; confirm • Tubes will be covered
Photosynthesis • “…converting light energy into chemical energy in the C-C & C-H bonds of sugar.”* * Freeman – fourth edition
Photosynthesis Light • 6CO2 + 6H2O C6H12O6 + 6O2
Fashioning an assay • Using the oxygen that plants belch out
Deflating, inflating a leaf • How can you tell if photosynthesis is happening? • What are the inputs? The products? • How can you test for these?
What’s in a leaf • Predict: what will we find when we grind up a leaf? • Protocol: p. 11-3 • Graph absorption of spinach extract • ‘ultra’-violet light it (high or low energy)? • Note!! These wavelengths re-do your DNA!!
Looking at a leaf, what would you hypothesize would be the most effective wavelengths for photosynthesis?(what is your mechanism?)
Homework • Table & Graph of absorbance data READ the rubric CAREFULLY! • Dilution worksheet (pp. 11-9 & 10)