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National Science Education Content Standards (Grades 9-12)

A—Science as Inquiry: Abilities necessary to do scientific inquiry1) Results of scientific inquiry--new knowledge and methods--

emerge from different types of investigations and public communication among scientists.

2) In communicating and defending the results of scientific inquiry, arguments must be logical and demonstrate connections between natural phenomena, investigations, and the historical body of scientific knowledge.

3) In addition, the methods and procedures that scientists used to obtain evidence must be clearly reported to enhance opportunities for further investigation.

B—Fundamental concepts and principles that underlie the conservation ofenergy and in disorder

E—Fundamental abilities and concepts used to identify a problem; propose a design and choose between alternative solutions; implement a proposed solution; and evaluate the solution and its consequences

G—History and Nature of Science—Nature of scientific knowledge. Scientific explanations must meet certain criteria.

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NY State Standards:

1. Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers, and develop solutions.• S1.1 Elaborate on basic scientific and personal

explanations of natural phenomena, and develop extended visual models and mathematical formulations to represent their thinking

• S1.2 The observations made while testing proposed explanations, when analyzed using conventional and invented methods, provide new insights into natural phenomena.

• E1.1 Initiate and carry out a thorough investigation of an unfamiliar situation and identify needs and opportunities for technological invention or innovation

2. Students will access, generate, process, and transfer information using appropriate technologies.

4. Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and recognize the historical development of ideas in science.

7. Students will apply the knowledge and thinking skills of science and technology to address real-life problems and make informed decisions.

Instructional Objectives

Students will be able to:

1. Describe a way to obtain electrical energy from an oxidation reduction (redox) reaction

2. Identify the parts of a voltaic cells and explain how each part operates

3. Calculate cell potentials and determine the spontaneity of redox reactions

4. Identify the parts of an electrolytic cell and explain how each part operates

5. Describe how electrolytic cells are different from voltaic cells

6. Explain some practical application of both voltaic and electrolytic cells

7. Explain how fuel cells work

8. Describe what conditions predispose towards the corrosion of metals

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Anticipatory Set

• Discuss/review concepts of electrical charges, ion formation, chemical equilibrium and oxidation reactions

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Motivation

Say, “Please carefully watch and listen to me as I take this lemon and insert two metallic strips: one Cu and one Zn into it. I am going to the attach a BLACK wire to the Zn strip and a RED wire to the Cu strip. The other ends of these wires are attached to a digital voltmeter. “

Ask, “What is happening with the meter?” Challenge->Think Pair Share with your nearest neighbor. Write down “ “How…” and “Why does all of this happen?”

Definitions:

CATHODE REDUCTION occurs at this electrode

ANODE

OXIDATION occurs at this electrode

But wait a moment, “What are oxidation and reduction?

Challenge, “How do these redox reactions affect the charge of each electrode?” “Why would an electric current be produced?” 6

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Development Part #1—Voltaic / Galvanic Cells

1. Demonstrate how Voltaic/Galvanic Cells work

2. Voltaic Cells use spontaneous oxidation-reduction reactions to convert chemical energy into electrical energy

3. Watch this animation carefully with your Think Pair Share partner

Ask, “Why is there an electriccurrent generated?” Andthen ask, “What is the purpose of the salt bridge?”

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4. Let the students carry out the following simulation with their laptops and the SmartBoard concomitantly.

Electrochemical Cells

Think Pair Share:

What variables appear to affect the magnitude ofelectricity produced inGalvanic cells?

Based on your knowledgeof chemistry, how could we calculate the amount of voltage being generat-ed?

Be sure to: Tabulate all your data, create useful graphs, and answer all of the questions?

e-

Ag+

Ag0

For every electron, an atom of silver is plated on the electrode.Ag+ + e- Ag0

Electrical current is expressed in terms of the ampere, which is defined as that strength of current which, when passed through a solution of AgNO3 (aq) under standard conditions, will deposit silver at the rate of 0.001118 g Ag/sec

1 amp = 0.001118 g Ag/sec

5. Describe the relationship between voltage and the motion of electrons

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Michael Faraday’s Law of Electrolysis

The mass deposited or eroded from an electrode depends on the quantity of electricity.

Quantity of electricity – coulomb (Q)

Q is the product of current in amps times time in seconds

Q = Itcoulomb

current in amperes (amp)

time in seconds

1 coulomb = 1 amp-sec = 0.001118 g Ag10

Ag+ + e- Ag

1.00 mole e- = 1.00 mole Ag = 107.87 g Ag

107.87 g Ag/mole e-

0.001118 g Ag/coul= 96,485 coul/mole e-

1 Faraday (F )mole e- = Q/F

mass = molemetal x MM

molemetal depends on the half-cell reaction

Faraday’s Law allowed us to determine the quantity of material deposited!!

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Part 1 Activities (continued)

6. Homework

a. Write up a “Simulation Report”. Be sure to answer all of the questions.

b.Be able answer some extended response questions on the theory and practical application behind

b. Galvanic (Voltaic) Cellsc. Electrolytic “d. Fuel “

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7. Closure Video

Watch and listen to this carefully!

Write out the answer to this: “When the Zn0 is oxidized, how does the fact that the reaction proceeds faster if heated relate to the spontaneity of the formation of the ZnO? How do this relate to the ΔG and Δε of the overall reaction?

Part #2—Electrolytic Cells +

Pose the following question:

“How do compounds like acids, bases and salts change the electrochemical properties of water when they’re added to it?” Elicit students’ responses while directing a basketball-type discussion. Follow-up with, “How does this explain why metal statues near the ocean tend to rust much quicker than ones equally close to the lakes and rivers?”

Motivation

Demonstrate electroplating of copper on to a zinc or iron electrode. Challenge your students by asking, “Why isn’t this a voltaic cell?” “How are these events different?” Elicit, “That for one thing electricity is not produced.” Say, “It’s an electrolytic process in which a cation is reduced and a solid metal is deposited on a surface.”

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Part #2—Lesson

1.You are going to break up into groups of four (Work Share Quads) and you will carry out a real-time lab experiment**:

Galvanic and Electrolytic Cells

Overview: Part A: Determining the Voltage of Electro-chemical

Cells Part B: Examination of Electrolytic cell using carbon

electrodes in a KI solution Part C: Electroplating Pennies and calculating

Faraday’s Law

**-Each group will only do two of the parts-A,B and/or C. I’ll come around and tell your parts. All groups will have to share their data with the other groups!!

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Part #2—Activities

2.Watch the next slide about the Hall Process

OK break up into your Work Share Quads as before and be able to answer these questions:

(a) Is this electrolytic or galvanic? Why?

(b) spontaneous or not spontaneous— Why? Now ask, “How could you prove it!

The Hall Process for …

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carbon-lined steel vesselacts as cathode

CO2 bubbles

Al (l)Al2O3 (l)

Drawoff Al (l)

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+

Cathode: Al+3 + 3e- Alo (l)

Anode: 2O-2 + Co (s) CO2 (g) + 4e-

frompowersource

Al+3

O-2

O-2

Al+3

O-2

graphite anodes

e-

e-

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Closure Activity Fuel Cells

Challenge, “How do fuel cells work? Are they more comparable to Galvanic or electrolytic cells or are they in a league all their own? Why? [Write out your answer!]

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Homework:

a. Review all of the concepts thoroughly!

b. Do the entire Lab Report

c. Students are to explain what

happens in the Hall Process.

d. Be sure to explain and account

for why the Al is deposited at one electrode and not the

other.

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Extra Credit-Individual Efforts Only

• Challenge, “How are Electrolytic and Voltaic cells different electrochemically and thermodyn- amically?”

•Describe what Cyclic Voltammetry and Chrono- amperometry are!

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Resources-Click diagrams for instantaneous access!

Periodic Table Electrochemistry Measurement of pH

1.

2.

3. Standard Electrode Potentials in Aqueous Solution at 25°C

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Here’s what Dr. Robert does in laboratories in other places:

How peculiar doctor, the cells seem to be multiplying randomly—come have a look for yourself!!!

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Acknowledgements• Claire J. Duggan, Center for STEM Education & Program Director of the RET @ Northeastern University

• Rocco Cieri, Medford Public Schools

• The RET Class of 2010

• Professor Patricia Ann Mabrouk, Chemistry and Chemical Biology Department@ Northeastern University

• Chemistry and Chemical Biology Department @ Northeastern University