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PASCO Spectrometer forBiology and Chemistry

Welcome! We’ll start at half past the hour.

Barbara PuglieseCurriculum & Professional Developmentbpugliese@pasco.com

Dr. Alex ToblerCurriculum & Professional Developmentatobler@pasco.com

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: support@pasco.com• 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

bpugliese@pasco.com | atobler@pasco.com