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Oxidation-Reduction

Oxidation-Reduction. Alexander Darmanin, Marcus Pabian & Lyn Cheah. Chemistry Stage 6 Syllabus. 9.2 Production of Materials 4. Oxidation-reduction reactions are increasingly important as a source of energy

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Oxidation-Reduction

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  1. Oxidation-Reduction Alexander Darmanin, Marcus Pabian & Lyn Cheah

  2. Chemistry Stage 6 Syllabus 9.2 Production of Materials 4. Oxidation-reduction reactions are increasingly important as a source of energy • identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metals • explain the displacement of metals from solution in terms of transfer of electrons • account for changes in the oxidation state of species in terms of their loss or gain of electrons

  3. Oxidation-Reduction In oxidation-reduction reactions (redox), changes of oxidation states occur between chemicals. 3 CuCl2(aq) + 2 Al(s) → ? • What happens in this reaction? • What IS an oxidation state? • What happens to the oxidation states? • What do YOU know about oxidation-reduction reactions?

  4. Go! • Materials 1 x 150ml beaker 1 x glass stirring rod 1 x Balance machine Calculate the grams of Copper chloride CuCl2granules 1 x 0.25 g Aluminum foil 50ml distilled water 50ml graduated cylinder • See work sheet for instructions Results visible in 5min • Safety • Wear lab coat, glasses and gloves • CuCl2is not that strong but don’t get It on you – when done use safe disposal bin NOT sink

  5. Think Which of the following best describes a reduction? The loss of electrons during a chemical reaction. The gain of electrons during a chemical reaction. The formation of copper during a chemical reaction. The loss Al during a chemical reaction. Which of the following best describes oxidation-reduction reactions? A reaction that involves the transfer of electrons from one species to another. A reaction that involves the formation of gases hydrogen and oxygen when two solutions are mixed. A reaction that involves the formation of solids when two solutions are mixed. A reaction that involves the neutralisation of H+ ions in solution.

  6. Results – what actually happens after 20 minutes

  7. Results • In terms of electron transfer: • In this reaction the Cu2+ ions have been converted into copper atoms • This requires Cu2+ ion to gain two electrons • Cu2+(aq) + 2 e- → Cu(s) • Electrons come from the Al3+ • The net result: • Copper ions come out of solution as Cu metal • Al goes into solution as an Al3+ ion • 3 Cu2+(aq) + 2 Al(s) → 3 Cu(s) + 2 Al3+(aq) • Half reactions: • Oxidation is the loss of electrons - Al is oxidised • Reduction is gain of electrons - Cu2+ is reduced • Simulation: Reduction of zinc by oxygen: http://www.youtube.com/watch?v=e6Xxz-VBE6s

  8. Dominant student misconceptions Oxidation and reduction misconceptions (taken from Garnett & Hackling, 1995 pp84): 6. The oxidation state of an element is the same as the charge of the monatomic ion of the element. 7. A polyatomic species can be assigned an oxidation state and this equals the charge on the species. 8. In all chemical equations the "addition" and "removal" of oxygen and hydrogen can be used to identify oxidation and reduction. 9. In all chemical equations the change in the charges of polyatomic species can be used to identify oxidation and reduction. 10. Oxidation and reduction processes can occur independently. What where your Misconceptions??? MORE MISCONCEPTIONS, FULL EXPLANATIONS, SOURCES + SIMULATIONS AT http://oxidationreductionactivity.wordpress.com

  9. Think What best describes an oxidation? What best describes a reduction? “Not all redox reactions involve oxygen, but all oxidation and reduction reactions involve transfer of electrons between substances” -Chemistry and chemical reactivity (6th edition) – first year chemistry textbook at UWS “the increase in oxidation state, is the only one that is universal to all oxidations” - Silverstein, 2011 “The only way oxidation-reduction equations can be identified with certainty is from changes in oxidation states” - Garnett, Garnett & Hackling, 1995

  10. The theory now Oxidising agent Reducing agent causes causes undergoes undergoes Reduction Oxidation Gain of electron Loss of electron can be defined as the Gain of hydrogen Loss of hydrogen But which one of these definitions is the most important and universal in all redox reactions? can be defined as the Loss of oxygen Gain of oxygen Decrease in oxidising state Increase in oxidising state

  11. The question is Electron transfer: Virtual or Literal Is it just a book keeping strategy Why is oxidation-reduction only taught as loss or gain of electrons in the Stage 6 syllabus? How will this affect further chemistry learning for the students?

  12. YouTube links: Reduction of zinc by oxygen: http://www.youtube.com/watch?v=e6Xxz-VBE6s Patterns of oxidation numbers across the periodic table: http://www.youtube.com/watch?v=EHe8-AFMsMA Determining oxidation numbers: http://www.youtube.com/watch?v=8_CvNPuuhiM&feature=related Turn copper into gold: http://www.youtube.com/watch?v=_g_ml8tAnWE&feature=relmfu The link to our blog again! http://oxidationreductionactivity.wordpress.com

  13. Anselme, J. (1997). Understanding oxidation-reduction in organic chemistry. Journal of Chemical   Education, Volume 74, Number 1, pg. 69 – 72. Brown, T. L., Lemay, H. E., Bursten, B. E. & Burdge, J. R. (2003). Chemistry The Central Science Ninth Edition International Edition. Prentice Hall: Australia, pg. 778 – 783.  Cox, A. L. & Cox J. R. (2002). Determining oxidation-reduction on a simple number line. Journal of Chemical Education, Volume 79, Number 8, pg. 965 – 967. Garnett, P. J., Garnett, P. J. & Hackling, M. W. (1995). Student’s alternative conceptions in chemistry: A review of research and implications for teaching and learning. Studies in Science Education, Volume 25, pg. 69 – 95. Garnett, P.J. & Treagust, D. F. (1992). Conceptual difficulties experienced by senior high school studentsof electrochemistry: Electric circuits and oxidation-reduction equations. Journal of Research in Science Teaching, Volume 29, Number 2, pg. 121 – 142. Hamza, K. & Wickman, P. (2008). Describing and analyzing learning in action: an empirical study of the importance of misconceptions in learning science. Science Education, Volume 92, pg. 141 – 164. Kotz, J.C., Treichel, P. & Weaver, G.C. (2006) Chemistry & chemical reactivity Edition 6th. Thomson Brooks/Cole: Belmont, California. Mole, P. (2006). Skepticism in the classroom A high school science teacher in trenches. Skeptic, Volume 12, Number 3, pg. 62 – 70. Moore, J. T. (2004). Chemistry Made Simple Revised Edition. Made Simple Books: USA, pg. 125 – 129. Nakhleh, M. B. (1992). Why some students don’t learn chemistry Chemical misconceptions. Journal of Chemical Education, Volume69, Number 3, pg. 191 – 196. Sanger, M. J. & Greenbowe T. J. (1997). Students’ misconceptions in electrochemistry: Current flow in Electrolyte solutions and the salt bridge. Journal of Chemical Education, Volume 74, Number 7, pg. 819 – 823. Sanger, M.J. & Greenbowe T. J. (1999). An analysis of college chemistry textbooks as sources of misconceptions and errors in electrochemistry. Journal of Chemical Education, Volume 76, Number6, pg. 853 – 860. Silverstein, T. P. (2011). Oxidation and reduction: Too many definitions? Journal of Chemical Education, Volume 88, Number 3, pg. 279 – 281. Talanquer, V. (2002) Minimizing misconceptions Tools for identifying patterns of reasoning. The Science Teacher, Volume 69, Number 8, pg. 46 – 49. Tarhan, L. & Acar, B. (2007). Problem-based learning in an eleventh grade chemistry class: ‘Factors affecting cell potential’. Research in Science and Technological Education, Volume 25, Number 3, pg. 351 – 369. References

  14. References Zoller, U. (1990). Comments and criticism Students’ misunderstandings and misconceptions in college freshman chemistry (General and organic). Journal of Research in Science Teaching, Volume 27, Number 10, pg. 1053 – 1065. Weblinks: AUS-e-tute n.d. (2011). Chemistry tutorial: Oxidation and reduction. Retrieved from: http://www.ausetute.com.au/redox.html Bodner Research Lab (2011). Oxidation and reduction. Retrieved from: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.php Clark, J. (2002). Definitions of oxidation and reduction (redox). Retrieved from:  http://www.chemguide.co.uk/inorganic/redox/definitions.html Greenbowe, T. J. (2003). Chemistry experiment simulations, tutorials and conceptual animations for introduction to college chemistry (aka general chemistry). Retrieved from: http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/animationsindex.htm Isis Publication (2003). 10.1 – Oxidation and reduction. Retrieved from: http://ibchem.com/IB/ibnotes/full/red_htm/10.1.htm mtchemers (2008). Oxidation numbers. Retrieved from: http://www.youtube.com/watch?v=EHe8-AFMsMA mtchemers (2008). Oxidation-reduction basics. Retrieved from: http://www.youtube.com/watch?v=e6Xxz-VBE6s NurdRage (2010). Turn pennies to silver and gold (Chemistry trick). Retrieved from: http://www.youtube.com/watch?v=_g_ml8tAnWE&feature=relmfu storm808b (2011). Determining the oxidation number of elements in a compound. Retrieved from: http://www.youtube.com/watch?v=8_CvNPuuhiM&feature=related

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