Monitoring a marine ecosystem in introductory chemistry Rachel Narehood Austin ACS 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 N2N2 Basic principles

Logistics 60 students – 3 sections of 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 (NH 3, NO 2 -, NO 3 - ) Minerals Alkalinity, pH, [O 2 (aq)] Weekly cycle Week 1: calibration curve + data point Week 2: data point Week 3: data point + quality control test

Methods PO (NH 4 ) 6 Mo 7 O 24  [Mo 12 O 36 (PO 4 )] NH 4 + [Mo 12 O 36 (PO 4 )] 3- + SnCl 2  Molybdenum Blue (  NO sulfanilamide + N-(1- napthyl)-ethyelendiamine dihydrochloride (NED dihydrochloride)  azo dye (  OH NH 3 + HOCl + MnSO 4 NOHO Indophenol (  Standard Methods for the Examination of Water and Wastewater 20 th Ed

Methods Dissolved oxygen (Winkler method) 4 Mn(OH)­ 2 + O H 2 O  4 Mn(OH) 3 4Mn(OH) I H +  4 Mn I H 2 O 2Starch-I­ S 2 O 3 2-  4 I - + 2S 4 O 6 2- Standard Methods for the Examination of Water and Wastewater 20 th Ed

Methods UV determination of NO 3 - coupled to IC determination ( =220)

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 The Conscientious Marine Aquarist, by Fenner, ISBN The New Marine Aquarium, by Paletta, ISBN Several appendices General Technical Comments (units, concentration/dilution, beers law, titrations, pipetters, quadratic equations) Chemical ConcentrationVolumeWaste Location MnSO 4 *. H 2 O0.05%Amount Disposed DRAIN

Selected Data 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