Oxidation-ReductionAlexander 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

• 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

Oxidation-ReductionIn 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?

Go!• Materials1 x 150ml beaker1 x glass stirring rod1 x Balance machineCalculate the grams of Copper chloride CuCl2

granules1 x 0.25 g Aluminum foil50ml distilled water50ml graduated cylinder

• See work sheet for instructionsResults visible in 5min

• SafetyWear lab coat, glasses and

gloves CuCl2 is not that strong but

don’t get It on you – when done use safe disposal bin NOT sink

Think

Which of the following best describes oxidation-reduction reactions?A.A reaction that involves the transfer of electrons from one species to another.B.A reaction that involves the formation of gases hydrogen and oxygen when two solutions are mixed.C.A reaction that involves the formation of solids when two solutions are mixed.D.A reaction that involves the neutralisation of H+ ions in solution.

Which of the following best describes a reduction?A.The loss of electrons during a chemical reaction.B.The gain of electrons during a chemical reaction.C.The formation of copper during a chemical reaction.D.The loss Al during a chemical reaction.

Results – what actually happens after 20 minutes

ResultsResultsIn 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 reducedSimulation:Reduction of zinc by oxygen:http://www.youtube.com/watch?v=e6Xxz-VBE6s

Dominant student Dominant student misconceptionsmisconceptions

What where your Misconceptions???MORE MISCONCEPTIONS, FULL EXPLANATIONS, SOURCES + SIMULATIONS AT

http://oxidationreductionactivity.wordpress.com

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.

ThinkWhat 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

Oxidising agent Reducing agent

Reduction

Gain of hydrogen Loss of hydrogen

Loss of electronGain of electron

Loss of oxygen

Oxidation

Decrease in oxidising state

Increase in oxidising state

Gain of oxygen

causes causes

undergoesundergoes

can be defined as theca

n be

def

ined

as

the

But which one of these definitions is the most important and universal in all redox reactions?

The theory now

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?

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

ReferencesAnselme, 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 6 th. 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, Volume 69, 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.

ReferencesZoller, 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