Lab 11: Light and Colors Building and confirming tools for inquiry

What is ‘color’ Is there a difference between your shirt and a neon light? Is there a difference between your shirt and a neon light?

Think With Me… Why do you see (different) colors when chemicals are flamed? Assertion I – unlike planets, electrons are only allowed discrete energies Assertion II – energies that don’t take electrons to an “allowed” place are ignored Why do you see (different) colors when chemicals are flamed? Assertion I – unlike planets, electrons are only allowed discrete energies Assertion II – energies that don’t take electrons to an “allowed” place are ignored

Hydrogen Atom Simulator Also in Further Explorations Predict what happens to an arbitrary energy photon Predict what happens to one that matches a difference between current and potential orbital

Types of evidence/arguments 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

How are these different? Using a thermometer to test temperature Pointing a stick, say magic words, wait for rain Using pH paper to count protons Using Ba(OH) 2 ‘test’ for CO 2 Counting ‘geigs’ with a Geiger counter Believing in ‘global climate change’

A black box? Or a tool?

The Parts Set for infinite absorbance (blocked path) Set wavelength Set zero absorbance

Tool using We have chalk at each station Place these in the specs (IN THE TUBE!) Look at the beam inside! Slowly (and carefully) move the wavelength selector What do you see? Reset spec to ‘correct’ wavelength We have chalk at each station Place these in the specs (IN THE TUBE!) Look at the beam inside! Slowly (and carefully) move the wavelength selector What do you see? Reset spec to ‘correct’ wavelength

Calibrating the tool (Pg. D-2) ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I mention the CORRECT wavelength? ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I mention the CORRECT wavelength?

The Parts 1.) Set CORRECT wavelength

Calibrating the tool (Pg. D-2) ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I say CORRECT? 2) Use ON/OFF knob to set needle to infinite absorbance ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I say CORRECT? 2) Use ON/OFF knob to set needle to infinite absorbance

The Parts 2) Set for infinite absorbance (blocked path)

Calibrating the tool (Pg. D-2) ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I say CORRECT? 2) Use ON/OFF knob to set needle to infinite absorbance 3) Clean BLANK tube and place in sample chamber. Close the lid. 4) Use “zero” adjustment knob to set needle to ZERO ABSORBANCE ***Take out test tube containing chalk*** 1) Set to CORRECT wavelength – did I say CORRECT? 2) Use ON/OFF knob to set needle to infinite absorbance 3) Clean BLANK tube and place in sample chamber. Close the lid. 4) Use “zero” adjustment knob to set needle to ZERO ABSORBANCE

The Parts Set zero absorbance

The Parts Set for infinite absorbance (blocked path) Set wavelength Set zero absorbance

Calibrating your eye Graph paper page I-9 Predict: how will a blue liquid absorb? A green one?

Do it Tubes in the rack Find the absorbance of each color at EACH wavelength MOVE to the next STATION = wavelength (DO NOT ALTER THE WAVELENGTH) Do you trust the other groups? each station

Do it Tubes in the rack Find the absorbance of each color at EACH wavelength MOVE to the next STATION = wavelength (DO NOT ALTER THE WAVELENGTH) Do you trust the other groups? each station Before you start, what should you do with your data?

Data Violet Blue Green Yellow Red Page I-1 in lab manual ABSORBANCES

Do it Tubes in the rack Find the absorbance of each color at EACH wavelength MOVE to the next STATION (wavelength) Do you trust the other groups? each station

Some Dye Structures Crystal Violet Yellow Napthol Green FDC Blue1 FDC Red 3 FDC Yellow5

Moving On

Remember ‘density’? What would you have to do to make a dye so that there were half as many collisions between dye molecules and the beam of light? Pick a stock solution: build a solution with ¼ absorbance of the stock. Confirm Is it consistent with all wavelengths?

Photosynthesis 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2

Photosynthesis: Intro

What’s in a leaf Predict: what will we find when we grind up a leaf? Protocol: p Graph absorption of spinach extract ‘ultra’-violet light it (high or low energy)? Note!! These wavelengths re-do your DNA!!

Flight of the electron

Fashioning an Assay How can you tell if photosynthesis is happening? What are the inputs? The products? How can you test for these? Protocol on 11-5; Exercise 4 (bullet points) –READ THOROUGHLY More information on 12-2

Fashioning an Assay Do you need a control?

Fashioning an Assay 1) Extract oxygen from leaves 2)Place deflated leaves in small beaker with buffer 3) Place beaker under lights 4) Control goes where?

Next week! You’ll take the data you have from this week to create a red-passing, blue- passing or green-passing solution This will be used to test whether different portions of the visible spectrum are equally potent for photosynthesis Sadava, Life, Fig. 8-6

Pg and Due in lab