Discovering Electrolytic Reactions
Name: Crystal Bell
Title of Lesson: Recharged
Date of Lesson: TBA
Length of Lesson: 2 days
Description of Class: H. S. Chemistry
Source of Lesson: Crystal Bell
TEKS addressed:
(5) Science concepts. The student knows that energy transformations occur during physical or chemical changes in matter. The student is expected to:
(A) identify changes in matter, determine the nature of the change, and examine the forms of energy involved;
(B) identify and measure energy transformations and exchanges involved in chemical reactions
(10) Science concepts. The student knows common oxidation-reduction reactions. The student is expected to:
(A) identify oxidation-reduction processes
The Lesson:
I. Overview
This lesson is meant to build on prior lessons that covered voltaic cells. Students will research how a car battery is recharged. This is just one of many examples of an electrolytic reaction.
II. Performance or learner outcomes
Students will be able to:
¤ Explain what an electrolytic reaction is
¤ Explain the reactions involved in recharging a lead acid battery
¤ Distinguish between a voltaic and electrolytic process
III. Resources, materials and supplies needed
For each class
1 - dead car battery attached to a car
1 - person willing to play the Òdistraught teacherÓ
IV. Supplementary materials, handouts
None
Five-E Organization
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Teacher Does |
Student Does |
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Engage: Why is the car battery dead? Learning Experience(s): A distraught teacher (preferably not the actual teacher for the class) will have a problem starting their car. They will ask the class if they can help.
The class will take a Òfield tripÓ to the parking lot to analyze the car. They will determine that a dead battery is the culprit.
The distraught teacher will want to know why the battery died. Students will be prompted to give a technical answer.
To fix the problem the dead battery will be jump started. |
Hoped for student response: Students will be excited to show off what they know about car batteries and how they work. They will eagerly explain the chemistry of how a battery works.
The students will know that the battery will work again if jumped. |
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Questions: What caused the battery to die? Explain it chemically.
Where is the cathode and the anode on the battery?
What happens at each electrode?
What is this battery made out of?
Can the battery be helped? Or does it have to be replaced? |
Expected student response:
Students will be a little confused initially, but will be excited about leaving the class. The teacher will have to keep everyone on task and involved in solving the problem.
The students will want to give simple answers and will have to be prompted to give a chemical explanation. |
Decision Point Assessment (DPA) Ð When the students have given an accurate electrochemical explanation and answered the questions the class will return to the classroom.
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Explore: Why can a car battery be recharged? Learning Experience(s): Students will be given a homework assignment to research why the car battery was able to be recharged.
They will write a one page paper that includes the half reactions and full reactions that led to the discharge and recharge of the battery.
They may use anything (textbook, internet, mechanic, etc.) as a resource, but they must work independently. A list of sources should be included on a separate page.
Students will be reminded that spelling and grammar matter and they are not to steal someone elseÕs work.
Questions: Can all batteries be recharged?
What type of battery was in the car?
Why was the car battery able to be recharged?
What are the half and full equations for the discharging of the battery? For the recharging?
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Hoped for student response: Students will be curious to learn why a dead battery could be revived. They will conduct thorough research and turn in detailed chemical explanations of what happened.
Expected student response: Although they may be curious, students will not want to write a paper. They will complain and some may try to plagiarize a published description. |
DPA: Students will turn in a paper on how batteries are recharged.
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Explain: What did you find? The class will discuss what different people found and learn about how and why electrons move to recharge a battery.
Students will be introduced to the difference between a voltaic and an electrolytic cell.
Questions: What are the redox reactions involved in the charging and discharging of this battery?
What is oxidized and reduced?
How is a battery recharged? Is it a spontaneous reaction? If not what makes it occur?
What is the difference between the types of cells we have been studying (voltaic) and the charging process?
Which direction to electrons flow in each type of cell?
Where are other places that an electrolytic cell would be used?
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Hoped for student response: Students will have thought through these questions in writing their papers and be prepared to describe how recharging works.
They will not use the term electrolytic, but will be ready to add that term to their description of what happened.
Expected Student Response: Students will give mixed answers about what took place and will have to reason through a solution in class.
Some students will not offer anything unless they are asked directly, so the teacher will need to pull them into the discussion. |
DPA Ð Students will be asked to draw a diagram of a voltaic cell and an electrolytic cell. They will label the cells and provide a brief description of how they are different.
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Extend / Elaborate: Finding Electrolysis The teacher will explain other ways electrolysis is commonly used and show the reactions involved.
Questions: How should the electrons move?
Where is oxidation occurring? Reduction?
What are the half reactions?
How many electrons are transferred in the balance equation?
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Hoped for response: This lesson is intended to come at the end of several lessons on batteries and electrochemistry. Students should be familiar with the terms and able to quickly identify where and how reactions are occurring.
Expected Student Response: Some students will still be having trouble sorting out the particulars, but they will be able to follow the descriptions. It should be fairly simple to direct them towards a correct answer. |
DPA Ð Students will write a Murkiest Point response on anything that might still be confusing.