Lesson Plan | Traditional Methodology | Electrochemistry: Batteries

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage is to provide students with a clear and detailed view of the learning objectives of the class, establishing expectations and directing attention to the main points to be comprehended. This will help structure students' thinking and focus on the essential concepts that will be developed throughout the class.

Main Objectives

1. Understand the concept of electrochemical cells and their function.

2. Identify and calculate the anode, cathode, and direction of current in a cell.

3. Determine the potential difference (pd) of a cell under standard conditions.

Introduction

Duration: (10 - 15 minutes)

The purpose of this stage is to capture students' attention and contextualize the topic within their daily lives. This will help make the content more relevant and interesting, facilitating the understanding of the concepts that will be developed throughout the class.

Context

Explain to students that electrochemistry is an important area of chemistry that studies the relationships between chemical reactions and electricity. Introduce the concept of an electrochemical cell, a device that converts chemical energy into electrical energy. Use everyday examples, such as the batteries we use in our cell phones, remote controls, and cars, to illustrate the relevance of this topic in students' daily lives.

Curiosities

Did you know that the first batteries were invented by Alessandro Volta in 1800? They were composed of stacked disks of copper and zinc, separated by cardboard soaked in brine. These primitive batteries were the basis for the development of modern batteries that we use today, such as lithium batteries in smartphones.

Development

Duration: (50 - 60 minutes)

The purpose of this stage is to deepen students' understanding of the functioning of electrochemical cells, providing a solid foundation in the concepts of oxidation and reduction, structure of a cell, and calculation of potential difference. Solving practical problems will allow students to apply theoretical concepts, consolidating their learning and preparing them for more complex questions.

Covered Topics

1. Structure of an Electrochemical Cell: Explain that a cell is composed of two electrodes (anode and cathode) and an electrolyte. Detail that the anode is the electrode where oxidation occurs and the cathode is the electrode where reduction occurs. 2. Oxidation and Reduction Reactions: Detail the concept of oxidation (loss of electrons) and reduction (gain of electrons). Provide simple examples to illustrate these processes. 3. Direction of Electric Current: Explain that the electric current in the cell flows from the anode to the cathode through the external circuit, while ions in the electrolyte complete the internal circuit. 4. Calculation of pd (Potential Difference): Teach how to calculate the pd of a cell using the standard reduction potentials of the electrodes. Show the formula: Eº_cell = Eº_cathode - Eº_anode. 5. Practical Example: Present a practical example of a Daniell cell (Zn/Cu) and demonstrate the calculation of the pd, identifying anode, cathode, and the direction of current.

Classroom Questions

1. Calculate the pd of a cell composed of a magnesium (Mg) electrode and a silver (Ag) electrode, whose standard reduction potentials are Eº(Mg²⁺/Mg) = -2.37 V and Eº(Ag⁺/Ag) = +0.80 V. 2. Identify the anode and cathode in a Zn/Cu cell and describe the direction of electric current. 3. Explain what happens to the ions in the electrolyte during the operation of an electrochemical cell.

Questions Discussion

Duration: (20 - 25 minutes)

The purpose of this stage is to review the solved questions, promoting a detailed and enlightening discussion to ensure that students fully understand the concepts covered. Engaging students with reflective questions and group discussions helps to consolidate learning, correct any misconceptions, and foster a collaborative learning environment.

Discussion

• Question 1: Calculate the pd of a cell composed of a magnesium (Mg) electrode and a silver (Ag) electrode, whose standard reduction potentials are Eº(Mg²⁺/Mg) = -2.37 V and Eº(Ag⁺/Ag) = +0.80 V.

• Explain to students that, to calculate the pd, the formula used is Eº_cell = Eº_cathode - Eº_anode. In this case:

• Eº_cathode (Ag⁺/Ag) = +0.80 V

• Eº_anode (Mg²⁺/Mg) = -2.37 V

• Therefore, the pd of the cell is Eº_cell = 0.80 V - (-2.37 V) = 3.17 V.

• Question 2: Identify the anode and cathode in a Zn/Cu cell and describe the direction of electric current.

• Clarify that, for the Zn/Cu cell, the standard reduction potentials are:

• Eº(Zn²⁺/Zn) = -0.76 V

• Eº(Cu²⁺/Cu) = +0.34 V

• The zinc (Zn) electrode has the lowest reduction potential, therefore it is the anode (where oxidation occurs). The copper (Cu) electrode is the cathode (where reduction occurs).

• The electric current flows from the anode (Zn) to the cathode (Cu) through the external circuit.

• Question 3: Explain what happens to the ions in the electrolyte during the operation of an electrochemical cell.

• Detail that during the operation of the cell, positive ions migrate towards the cathode to neutralize the excess negative charges, while negative ions migrate towards the anode to neutralize the excess positive charges. This maintains the electrical neutrality of the solution and allows for the continuity of the electrochemical reaction.

Student Engagement

1. Why is the anode always the electrode where oxidation occurs? 2. How would the pd of a cell be affected if the reduction potentials of the electrodes were different? 3. What are the practical applications of electrochemical cells in our daily lives? 4. How would you explain to a friend the difference between a cell and a battery? 5. What would be the implications if the electrolyte of a cell was removed or replaced?

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage is to reinforce the main concepts covered in the class, ensure that students understand the connection between theory and practice, and highlight the relevance of the topic to everyday life. This helps consolidate the learning and motivates students to apply the knowledge acquired in practical situations.

Summary

• Understanding the concept of electrochemical cells and their function.
• Identification and calculation of the anode, cathode, and direction of current in a cell.
• Determination of the potential difference (pd) of a cell under standard conditions.
• Structure of an electrochemical cell, oxidation and reduction reactions, and the flow of electric current.
• Practical example of a Daniell cell (Zn/Cu) and calculation of the pd.
• Discussion about the role of ions in the electrolyte and practical implications.

The class connected theory with practice through everyday examples, such as cell phone batteries and remote controls, as well as a detailed example of a Daniell cell. This helped students see the real application of theoretical concepts, making the content more accessible and relevant.

Knowledge about electrochemical cells is crucial to understanding many technologies we use daily, from common batteries to lithium batteries in smartphones. Understanding these concepts allows students to recognize the importance of chemistry in modern life and appreciate technological innovations.