ELECTRON TRANSFER REACTIONS: OXIDATION AND REDUCTION
Redox reactions provide a logical and consistent explanation of the previous reaction generalizations of formation, simple decomposition, complete combustion, and single displacement. It is important for students to understand that, although many reaction types can be explained as redox reactions, some types are obviously not redox.
The central concept in this chapter is that redox reactions involve a transfer of electrons from the strongest reducing agent to the strongest oxidizing agent in the chemical system.
The central concept in this chapter is that redox reactions involve a transfer of electrons from the strongest reducing agent to the strongest oxidizing agent in the chemical system.
Learning Objectives
By the end of this lesson, I will:
· Understand the terms “reduction” and “oxidation” as they relate to electron transfer.
· Know how to identify and assign the oxidation number of an atom in a compound or ion.
· Be able to identify reducing and oxidizing agents.
· Know how to write half-reaction equations.
· Understand the terms “reduction” and “oxidation” as they relate to electron transfer.
· Know how to identify and assign the oxidation number of an atom in a compound or ion.
· Be able to identify reducing and oxidizing agents.
· Know how to write half-reaction equations.
Lesson Approaches and Overview (Specific Expectations: F2.1, F2.2, F3.1)
- The following activity can be used to introduce the lesson, or as a hook:
· Ask the students to try to bring coke cans to class.
· Ask students to try to break apart their Coke cans. Tell them that you have superhuman strength, and proceed to break yours apart (these are the cans that have been chemically treated).
· Explain to the students that the can you ripped apart was prepared, and that a reaction called “redox” reaction is responsible for it.
· Watch the following video which explains what happens to the can. Video is embedded below, after "How Does it Work" link.
· Read the “How does it work” section of following link:
· Brainstorm with the students to come up with a list of chemical reactions in any context and then classify the reactions as electrochemical or not. The point to be made is that most natural and technological chemical reactions are electrochemical. Students can be reminded that most of the reactions they have encountered are redox reactions, except for neutralization and precipitation reactions.
· To teach the concept of single displacement reactions, the following lab is recommended:
· To teach the concept of single displacement reactions, the following lab is recommended:
For computer simulations on single displacement reactions, any of the following activities is highly recommended:
In addition to the above demonstration, it is a good idea to place a petri dish in a clean strip of metal into an ionic solution. Set this petri dish on an overhead projector and project the growth of crystals onto the screen. This provides a good opportunity for discussion and re-enforcement of learned concepts.
· The following video is a great introduction to the concept of redox reactions:
· The following video is a great introduction to the concept of redox reactions:
- The following PowerPoint presentation can be used for the lecturing part of the lesson:
· To help memorize and understand the theoretical definitions, use the following mnemonics:
OIL RIG = “Oxidation involves loss – Reduction involves gain”
LEO says GER = “Loss of electrons is oxidation and gain of electrons is reductions”
OAR and REO = “Oxidizing agents are reduced and reducing agents are oxidized”
· To learn about oxidation numbers, the “rules” for determining oxidation numbers must be memorized, as well as the common oxidation numbers. The following video is recommended:
OIL RIG = “Oxidation involves loss – Reduction involves gain”
LEO says GER = “Loss of electrons is oxidation and gain of electrons is reductions”
OAR and REO = “Oxidizing agents are reduced and reducing agents are oxidized”
· To learn about oxidation numbers, the “rules” for determining oxidation numbers must be memorized, as well as the common oxidation numbers. The following video is recommended:
It is important that students are explained the relationship between oxidation, reduction and oxidation numbers: Oxidation is the increase in oxidation number, while reduction is the decrease in oxidation number.
· To reinforce the concept of oxidation numbers, the following games are recommended:
· To reinforce the concept of oxidation numbers, the following games are recommended:
The following is a game called "Oxidation Bingo" that can be used in this section of the lecture, or as a consolidating activity:
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Here is a very interesting idea that will give students practice with the assignment of oxidation numbers. I am including three files: The Cards, the instructions, and the recording sheet:
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· As a consolidation activity or homework, ask students to choose a local chemical industry and investigate the electrochemical reactions involved in this industry. Ask students to present their research, and how it relates to the concepts learned. Also, any of the oxidation number games, the oxidation bingo game, and/or the oxidation trump cards game can be used as a consolidation.
References
- Image on top retrieved from: http://www.google.ca/imgres?imgurl=http://academic.pgcc.edu/~kroberts/Lecture/Chapter%25205/05-02_RedoxReactions_L.jpg&imgrefurl=http://academic.pgcc.edu/~kroberts/Lecture/Chapter%25205/redox.html&h=546&w=1236&sz=80&tbnid=M_QSHG2iakMnCM:&tbnh=56&tbnw=127&zoom=1&usg=__AVU_QsOyivfSqqoKcHB872KY_lc=&docid=CaOJbVi0L3n2AM&sa=X&ei=1KhLUfmWCbe-4AOhnoCIAQ&ved=0CDcQ9QEwAg&dur=3171
- Di Guiseppe, M., Haberer, S., Salciccioli, K., Sanader, M, Vavitsas, A. (2012) Chemistry 12. Toronto: Nelson Education Ltd.
- van Kessel, H., Jenkins, F., Davies, L., Plumb, D., Di Guiseppe, M., Lantz, O., Tompkins, D. (2003). Chemistry 12. Toronto: Thomson Canada Limited