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Transcript of Monitoring a marine ecosystem in introductory chemistry Rachel Narehood Austin ACS Meeting Boston...
Monitoring a marine ecosystem in introductory chemistry
Rachel Narehood AustinACS Meeting
Boston August 2002
Context for change: Introduce new intro chem sequence (CHEM
107b/CHEM 108b)
CHEM 107 “Atomic and molecular structure”
CHEM 108 “Chemical Reactivity”
CHEM 107b “Chemical Structure and its importance in the environment”
CHEM 108b “Chemical Reactivity in environmental systems”
CHEM 108b “Chemical Reactivity in Environmental Systems”
Using biogeochemical cycles to teach chemistry Nitrogen cycle: thermodynamics Carbon cycle: equilibria (including
solubility and acid base) Sulfur cycle: redox chemistry Oxygen: kinetics
N2
Basicprinciples
Logistics
60 students – 3 sections of 20
125 gallon salt water aquarium w/UV sterilizer, acrylic tank, sump, ballasts with actinic and lanthanide bulbs on timers, submersible heater, venturi protein skimmer
11 weeks of lab Week 1: intro to excel,
Beer’s law refresher Week 2: technical training Weeks 3,4, & 5: rotation 1 Weeks 6, 7, & 8: rotation 2 Weeks 9, 10, & 11: rotation 3 Modified from Ken Hughes –
Analytical chemistry
Lab Structure Group tasks
Nitrogen cycle (NH3, NO2-, NO3
-) Minerals Alkalinity, pH, [O2(aq)]
Weekly cycle Week 1: calibration curve + data point Week 2: data point Week 3: data point + quality control
test
Methods PO4
3- + (NH4)6Mo7O24 [Mo12O36(PO4)]
3- + 3 NH4+
[Mo12O36(PO4)]3- +
SnCl2Molybdenum Blue (
NO2- + sulfanilamide + N-(1-
napthyl)-ethyelendiamine dihydrochloride (NED dihydrochloride) azo dye (
OH
NH3 + HOCl + MnSO4 N OHO
Indophenol
(
Standard Methods for the Examination of Water and Wastewater 20th Ed
Methods Dissolved oxygen
(Winkler method)4 Mn(OH) 2 + O2 + 2 H2O 4
Mn(OH)3
4Mn(OH)3 + 4 I- + 12 H+ 4 Mn2+ + 2I2 + 12 H2O
2Starch-I 2 + 4 S2O32- 4 I- +
2S4O62-
Standard Methods for the Examination of Water and Wastewater 20th Ed
Lab Manual Detailed procedures given
Students are encouraged to check other sources Detailed procedures for hazardous waste
Minimal background (refs. on reserve)Natural Reef Aquariums , by Tullock, ISBN 1-890087-01-7The Conscientious Marine Aquarist, by Fenner, ISBN 1-890087-02-5
The New Marine Aquarium, by Paletta, ISBN 1-890087-52-1 Several appendices
General Technical Comments (units, concentration/dilution, beers law, titrations, pipetters, quadratic equations)
Chemical Concentration Volume Waste Location
MnSO4*.H2O 0.05% Amount
DisposedDRAIN
Marine Aquarium Weekly Report
Week of _________________
Test Monday PM Tuesday AM Tuesday PM
Group A Ammonia < 1 ppm
Nitrite < 1 ppm
Nitrate 0-20 ppm (lower is better)
Group B Phosphate 1.0-3.0 ppm
Sulfate 2700 ppm
Calcium 400 ppm
Magnesium 1350 ppm
Group C Salinity 19 ppt Cl
Alkalinity 125-250 ppm CaCO3
Dissolved Oxygen 5-7 ppm
Overview pH Temp Specific gravity
Selected Data
0
1
2
3
4
5
6
7
0 2 4 6 8 10
weeks
[ ]
pp
m ammonia
nitrate
average for one class
standard deviation (+/-) for one class
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
1 2
[Nit
rate
] p
pm
Student data facilitates detailed monitoring of tank
Variability is large between groups
Assessment Required sections (10-15 pages, one per group)
Abstract Introduction Experimental Section Results. Discussion and Conclusion
Grading Each lab 100 points - 10 points: title/signatures; abstract; intro;
exp.; results; discussion, graphs/data presentation; writing/typos; effort
Peer review of rough draft (each student does one per semester) Final grade 90% lab grade, 10% effort – individual assessment,
group assessment, peer review, my assessment
Acknowledgements
Lab development: Ken Hughes, Michael Danahy, Lorna Clark, Gary Starzynski, Kathy Covert,
Images: Hilary Domush, Brent Mann, Dana DiGiando, Elizabeth Lewis, Gary Starzynski
Funding: NSF (CCLI), NSF (Molecular Sciences Institute), Bates College (faculty development funds), Bates College/AACU (SENCER development funds), Kroepsch Teaching Award