LAB 11
Tools of
light trade
Instructor: Pedro Rodrigues
Today:
- Color properties
LAB 12 - Photosynthesis
- Tools
Remember this? What is color?
Wavelengths (nm)
Gamma X-rays Ultrarays
violet
Shorter
wavelength
Infrared
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
If your shirt is blue, what does that mean?
Wavelengths (nm)
Gamma X-rays Ultrarays
violet
Shorter
wavelength
Infrared
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
From: http://www.neonstreet.com
What do you know about how
light is created in Fireworks?
Neon light?
Hydrogen Atom Simulator (by Dan Damelin)
Lab homepage -> further exploration -> Lab11 -> first link
•
http://chemsite.lsrhs.net/FlashMedia/html/flashEMR.htm
http://www.scifun.org/chemweek/gasemit/gasemit.html
http://scifun.chem.wisc.edu/chemweek/fireworks/fireworks.htm
http://www.youtube.com/watch?v=S9dqJRyk0YM
What do you see?
Think about photosynthesis: what would these peaks
in absorption mean?
(think in what you know about colors)
TOOL USING
Critical thinking: how confident would you be
about the results you can get from these
devices/techniques?
•
•
•
•
•
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
TOOL USING
Critical thinking:
• 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 of that authority
THE SPECTROPHOTOMETER
If this machine works, what absorbance pattern
would you expect to find for objects that are green?
- Protocol for chlorophyll extraction on 11-3 and
11-4 (Exercise 2)
- Don’t start yet!
Calibration is critical!
Lower scale is absorbance
Chamber
1
2
Kimwipe test tubes!
Always close chamber
door first!
1. With empty
chamber, set
absorbance to
“infinity”
2. Insert reference
tube (transparent)
and set absorbance
to zero
3. Before using any
machine: recheck all
knobs.
Write down these steps
Lower scale is absorbance
Chamber
1
2
Kimwipe test tubes!
Always close chamber
door first!
1. With empty
chamber, set
absorbance to
“infinity”
2. Insert reference
tube (transparent)
and set absorbance
to zero
3. Before using any
machine: recheck all
knobs.
- Protocol for chlorophyll extraction on 11-3 and
11-4 (Exercise 2)
- Bring absorbance closer to 1
(not 2 as the lab manual states)
How do you bring down
absorbance?
Dilution problem
• What fraction of molecules would you have to remove from
a dye solution for there to be 1/4 as many collisions with a
detector beam? Think with a partner.
- Protocol for chlorophyll extraction on 11-3 and
11-4 (Exercise 2)
- Bring absorbance closer to 1
(not 2 as the lab manual states)
- DO IT (please)!
•
•
•
Predict what the
absorbance
pattern will be for
a blue, green, and
red dye.
I want to see 3
graphs; label your
axes
Graph paper is in
the manual, I-9
Collect dye absorbance data
Blue
Violet
Red
Green
Yellow
350
430
500
590
630
660
Make this table, use paper from appendix I-1
(include one column for Chlorophyll)
Representing data is important in science, thus your homework.
Calibration is critical!
Lower scale is absorbance
Chamber
1
2
Kimwipe test tubes!
Always close chamber
door first!
1. With empty
chamber, set
absorbance to
“infinity”
2. Insert reference
tube (transparent)
and set absorbance
to zero
3. Before using any
machine: recheck all
knobs.
What you are going to do:
• Tubes in the rack (including the
chlorophyll you extracted)
• Find the absorbance of each color at
each spec. station
• MOVE to the next wavelength (I will
count 4 min for each station, and then we
rotate groups in each station).
The data you collect are very important
•
•
•
•
You will use the data next week
If they’re wrong, everything will be wrong next week!
Take your time and do it right; it’s not a race
Today’s and next week’s work will lead to a write-up
that counts 7% of your grade
Photosynthesis (the simple version)
Photosynthesis (the simple version)
Last week we have got results consistent with fermentation.
Today let’s make a simple test for photosynthesis.
Photosynthesis (the simple version)
Last week we have got results consistent with fermentation.
Today let’s make a simple test for photosynthesis.
Will it float?
- Buffer: “friendly” environment for the leaves (pH and osmotic balance)
- How to get the air from the leaves?
Homework
1.
Tables and graphs of absorbance data
-
2.
Rubric: http://blc.arizona.edu/courses/181Lab/Rubrics/Light_Tools_rubric.pdf
Individual submission
Submit hard copy in lab
Microsoft Excel is good, if hand drawn make it NEAT
Dilution worksheet (pp. 11-9 & 11-10 in lab manual)
- Individual submission (you can start now)
3.
Project report (due Nov. 29th).