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PASCO Spectrometer forBiology and Chemistry
Welcome! We’ll start at half past the hour.
Barbara PuglieseCurriculum & Professional [email protected]
Dr. Alex ToblerCurriculum & Professional [email protected]
Your Facilitators
• Introduction to the Spectrometer and Spectrometry software• Colored solutions• Beer’s Law• Plant pigments & fluorescence• Kinetics: Reaction order• Reaction rate: Enzyme activity• Atomic spectra (fiber optic accessory)
Agenda
• PASCO’s Wireless Spectrometer (domestic) at pasco.com/spectrometer • Product specs• Free lab activities
• Pair through device settings first• ID on bottom• Suggestion: Number class set devices and spectrometers
• Open FREE PASCO Spectrometry app (go to app store or pasco.com/downloads)
Connecting the Spectrometer
What information can spectrometry reveal about a colored solution?
Colored Solutions
PREDICT: -What color is this solution?-Is the solution made from the skin ofa blueberry, lemon, lime, tangerine,or strawberry?
Colored Solutions
PREDICT: -What color is this solution?
Colored Solutions
How is the absorbance of a colored solution related to the amount of dissolved solute?
Beer’s Law
The absorbance (A) of a dilute solution is directly proportional to its concentration (c).
A ∝ cA = e l ce = molar absorptivity (L/cm·mol)l = path length through solution in cuvette (cm)c = concentration (mol/L)
The spectrometer determines A; l = 1 cm; and e = how strongly light is absorbed at a given wavelength for a given solution
Beer’s Law
Students may try:
-Rearranging the slope equation: y = mx + b…
x = (y - b)/m-Ratio or average ratio -Move the graph to find x-coordinate at the absorbance-Wild guess L
Beer’s Law
to = 5-10% error
to = below 5% error
Beer’s Law
x= above 10% error
Which wavelengths of light does each pigment absorb?
Why is chlorophyllgreen?
Plant Pigments
Plant Pigments
chlorophyll achlorophyll b
carotenoids chlorophyll a
chlorophyll b
What do plant pigment molecules do with excess energy?
Source: NASA, retrieved Nov 4, 2019 from https://www.nasa.gov/topics/earth/features/fluorescence-map.html
Plant Pigments: Fluorescence
Extension ideas:-How does the pigment absorbance spectrum of a tree’s leaves in summer compare to theabsorbance spectrum of its fall leaves?-Can you increase the stability of a pigmentby changing solvent? Storage temp.? Light?-Are there differences in pigment distribution in shade-adapted vs. sun-adapted plants?-What do CAM plant pigment distributions look like compared to C3 & C4 plants?
Plant Pigments
How can a change in absorbance indicate reaction order?
Kinetics: Reaction Order
zero order first order second order
What’s behind the QuickCalcs button?
Kinetics: Reaction Order
Order Linear Plot If this order is most linear, then Δ[reactant] …
Zero [Abs] v time …no effect on initial reaction rate; rate is constant
First ln[Abs] v time …directly affects initial reaction rate (if [doubled], rate doubles)
Second 1/[Abs] v time …exponentially affects reaction rate ([doubled], rate quadruples)
Further Inquiry:
-Change concentration or temperature of reactants
-Use a different reactant- phenolphthalein
Kinetics: Reaction Order
How is the rate of disappearance of H2O2 affected by an enzyme?
Catalyzed decomposition: 2H2O2(l) → 2H2O(l) + O2(g)
Catalyzed redox reaction: 4H2O2(l) + 4 guaiacol → tetraguaiacol + 8H2O(l)
Enzyme Activity
Mn, catalase
peroxidase
Clear
Brownish-yellow
Further inquiry:
-How do exposure to varied pH and temperature conditions affect enzyme activity? What kinds of ranges can peroxidase tolerate?
-How does substrate concentration affect enzyme activity? Does one substrate have more of an effect than the other?
Enzyme Activity
DPIP: 2,6-dichlorophenolindolphenol
DPIP (blue) + 2H+ + 2e– →Reduced DPIP (colorless)
Absorbance vs. Time: Plant Pigments
Bicarbonate pH indicator
Absorbance vs. Time: Photosynthesis & Respiration
Respiration Photosynthesis
What does a light emission spectrum tell us about atomic structure?
Atomic Spectra
Position the fiber optic cable steadily in place, perpendicular to the light source, but nottouching it.
The fiber optic cable is a separate accessory.
Atomic Spectra
Engage:
-What’s the frequency of a particular emitted photon? What’s its energy? What energy transition does it represent?
-What’s the substance that emits light in a glowing pickle?
Atomic Spectra
• Website resources• Spectrometer info & free labs
pasco.com/spectrometer • Free Spectrometry software
pasco.com/downloads/spectrometry
•Videos• PASCO Scientific YouTube channel
youtube.com/pascoscientific• Videos on pasco.com
pasco.com/videos• How Do I channel on YouTube
youtube.com/pascohowdoi
•Social • Twitter
@pascoscientific• Facebook
facebook.com/pasco.scientific
Resources• PASCO training• More free, live online trainings
pasco.com/resources/training/online• Onsite training/workshops
pasco.com/resources/training/workshops
• PASCO people & support• Teacher/technical support• email: [email protected]• phone: 800-772-8700• tech notes & FAQs
pasco.com/support/technical-support/technote • Find your regional sales rep
pasco.com/support/customer/find-your-rep• Barbara Pugliese | Dr. Alex Tobler