Qualitative Analysis (4C): A Foundation for Lab Skills Concept Presentation Tuesday, July 13, 2010 C. Burt

Presentation Outline Introduction Instructional Approaches Curriculum Expectations Student Demographic Instructional Approaches Misconceptions Textbook Issues Assessment & Evaluation References

What is Qualitative Analysis?

Qualitative Analysis http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/STILLS/FEZNSUL/FEZNSULF/64JPG48/6.JPG http://edu.glogster.com/media/1/9/42/67/9426718.jpg http://www.gettyimages.ca/detail/200448588-001/Riser?language=en-US&location=CAN

Curriculum Expectations B2.3 investigate precipitation reactions and flame tests, using qualitative analysis instruments, equipment and techniques [PR, AI] B2.4 conduct qualitative analysis of an unknown sample, using a flow chart and experimental procedures, including flame tests and precipitation reactions to determine the presence of metal ions [PR, AI] B2.5 identify an unknown gas sample by observing its emission spectrum and comparing it to the spectra of known gases [PR, AI]

What does it look like? http://gabudjr.files.wordpress.com/2009/11/flammes_colorees_petit.jpg http://staff.norman.k12.ok.us/~cyohn/index_files/ddlab_files/image001.jpg

What does it look like? http://www.physics.umd.edu/courses/Phys401/bedaque07/discrete_spectra.jpg

Who are the Students? SNC2D Grade 10, Academic SCH4C Grade 12, College Discuss what they should know SNC2P Grade 10, Applied

Why is it important? Forensics Fireworks Food/Water Quality Analysis identification of unknown materials association of unknowns to potential sources Fireworks production of colourful pyrotechnic displays for entertainment purposes Food/Water Quality Analysis contamination recognition toxicity testing Astronomy indirect identification of atoms on celestial objects

Instructional Approaches

Course Context Matter & Qualitative Analysis = first unit of SCH4C review the periodic table, symbols and atomic theories foundation for the remainder of the course (Shamai and Stavy, 1986) develop good lab skills

Proposed Sequence – Lesson #1 Review physical properties of matter Relate unique chemical structure to qualitative properties examine solids and solutions Introduce the flame test as a qualitative technique compare solution colours to flame colours demonstrate technique for lab disclose what they need to show for evaluation

impossible to differentiate between white powders Misconceptions impossible to differentiate between white powders colour of solid and solution is identical or similar to that of the flame test colour

Demo / Display #1

Textbook Tables Flame Colour Solution Colour Ion Symbol Colour lithium red sodium Na+ yellow potassium K+ violet cesium Cs+ calcium Ca2+ strontium Sr2+ barium Ba2+ yellowish-green copper Cu2+ bluish-green boron B2+ green lead Pb2+ bluish-white Solution Colour Ions Symbol Colour chromium (II) copper (II) Cr2+ Cu2+ blue chromium (III) copper (I) iron (II) nickel (II) Cr3+ Cu+ Fe2+ Ni2+ green iron (III) Fe3+ pale yellow cobalt (II) manganese (II) Co2+ Mn2+ pink Chemistry 11, McGraw-Hill Text

Remake the Tables! have the students make the tables encourage good lab skills allow them to test multiple times Ions Symbol Colour chromium (II) copper (II) Cr2+ Cu2+ blue chromium (III) copper (I) iron (II) nickel (II) Cr3+ Cu+ Fe2+ Ni2+ green iron (III) Fe3+ pale yellow cobalt (II) manganese (II) Co2+ Mn2+ pink http://www.cwcompliance.com/whmis_flammable.jpg

Proposed Sequence – Lesson #2 Pre-lab preparation Conduct lab students generate their own tables Practice assessment students use their generated tables with unknown samples can self-assess whether their tables were poor or helpful test household solutions

Proposed Sequence – Lesson #3 Introduce precipitate formation as a qualitative technique demo #2

Demo #2

Proposed Sequence – Lesson #3 Introduce precipitate formation as a qualitative technique demo #2 Review terms (soluble, insoluble, aqueous) Demonstrate how to read solubility tables Experiment with various dropper bottles and spot plates allow students time to see reactions and associate solubility table

Textbook Table – Example #1 http://castlelearning.com/review/reference/chem%20table%20f.gif

Textbook Table – Example #2 http://www.professormeyer.com/images/solubility%20chart.jpg

Textbook Table – Example #3 Anions Cl- Br- I- S2- OH- SO42- CO32- PO43- SO32- C2H3O2- NO3- High Solubility (aq) ≥ 0.1 mol/L (at SATP) most Group 1 Group 2 NH4+ Sr2+ Ba2+ Tl+ all All Group 1 compounds, including acids, and all ammonium (NH4+) compounds are assumed to have high solubility in water. Low solubility (s) < 0.1 mol/L (at SATP) Ag+ Pb2+ Hg22+ (Hg+) Cu+ Ca2+ Ra2+ none Cations

Solubility Song

Evaluation Standard pen & paper test (I) Practical test (K / I) Make a fire log which burns in a specific colour sequence. (A) Identification of ions in drinking water (I) http://image09.webshots.com/9/8/54/94/111785494sGJSSV_fs.jpg

References Ministry Documents – Grade 11 and 12 Science Shamai, R. and Stavy, R., Teaching an Introductory Course in Qualitative Analysis in Order to Enhance Learning General Chemistry, J. Chem. Educ., 1986, 63 (8), p 707 Chemistry 12 College Preparation, Nelson Text, 2004 Chemistry 11, McGraw-Hill Text, 2001 www.otfchemistry.webs.com