Objectives (5 - 7 minutes)

1. Understanding the Concept of Oxidation Number: Students should be able to understand the concept of oxidation number and its importance in chemistry. They should be able to describe what the oxidation number is and how it is determined for an element in a compound.

2. Calculation of Oxidation Number: Students should be able to calculate the oxidation number of an element in a compound using the rules of assigning oxidation numbers. They should be able to apply these rules to determine the oxidation number of elements in various examples.

3. Identification of Oxidation and Reduction Reactions: After understanding and being able to calculate the oxidation number, students should be able to identify oxidation and reduction reactions. They should be able to identify which elements are being oxidized and which are being reduced based on their changes in oxidation number.

Secondary Objectives

• Practical Application: Students should be able to apply the concept of oxidation number and their calculation skills to solve practical problems and real-world situations involving oxidation and reduction reactions.

• Critical Thinking: The study of oxidation number should encourage students to develop critical thinking skills, including the ability to analyze and interpret information, make connections between concepts, and apply the acquired knowledge to solve complex problems.

Introduction (10 - 15 minutes)

1. Review of Necessary Concepts: The teacher should start the lesson by briefly reviewing the concepts of atoms, ions, and how chemical bonding occurs. This is essential for students to understand and calculate the oxidation number. (2 - 3 minutes)

2. Problem Scenarios: Next, the teacher should present two problem scenarios that will help contextualize the importance of the oxidation number. For example:

   • "How does rust form on an iron nail exposed to air and moisture?" (Oxidation problem scenario)
   • "Why doesn't the battery of our cell phone last forever?" (Reduction problem scenario) (3 - 4 minutes)

3. Contextualization: The teacher should explain that the oxidation number is essential for understanding oxidation and reduction reactions, which are present in many chemical processes in our daily lives, including metal corrosion, energy production in batteries, photosynthesis, among others. This will help show students the relevance of the content that will be studied. (2 - 3 minutes)

4. Introduction of the Topic: To spark students' interest, the teacher can introduce the topic by sharing two curiosities:

   • "Did you know that the oxidation number of an element can vary depending on the compound it is in? For example, the oxidation number of carbon in glucose is different from the oxidation number of carbon in carbon dioxide."
   • "What if I told you that our body undergoes numerous oxidation and reduction reactions all the time to produce energy and keep our organism functioning?" (3 - 4 minutes)

5. Lesson Objectives: Finally, the teacher should present the Lesson Objectives, explaining that students will learn to calculate the oxidation number of an element in a compound and identify oxidation and reduction reactions. (1 minute)

Development (20 - 25 minutes)

1. Activity "Oxidation and Reduction in Our Daily Lives": (10 - 12 minutes)

   • Scenario: The teacher divides the class into groups of five and presents the following situation: "You are a team of scientists working at a research company for new materials. Recently, you have been hired to develop a new type of battery that has greater durability and less environmental impact. For this, you need to better understand oxidation and reduction reactions and how they are present in different materials and substances in our daily lives."
   • Task: Each group receives a list of common items (such as a cell phone battery, an iron nail, an apple cut in half, etc.) and the task of identifying which oxidation and reduction reactions are occurring in each of them. They must justify their answers, indicating which elements are being oxidized and which are being reduced, and calculate the oxidation number of an element in each reaction.
   • Materials: The teacher should provide symbolic laboratory materials to help students visualize the reactions (such as playdough balls to represent atoms, magnets to represent electrons, etc.).
   • Discussion: After the activity, the teacher should lead a classroom discussion where each group shares their findings and what they have learned about oxidation, reduction, and oxidation number.

2. Activity "Hunt for the Oxidation Number": (10 - 12 minutes)

   • Scenario: The teacher presents the following situation: "You are archaeologists in an excavation of an ancient civilization and have found a parchment with chemical formulas. It is believed that these formulas are from ancient potions that were used to cure diseases. However, to understand how these potions work, you need to be able to calculate the oxidation number of each element in the formulas."
   • Task: Each group receives a series of chemical formulas and the task of calculating the oxidation number of each element. The formulas should be complex enough to challenge the students, but not so complex as to be discouraging. Students should work together to solve the formulas, helping each other understand the concept of oxidation number and apply the rules of assigning oxidation numbers.
   • Materials: The teacher should provide a list of rules for assigning oxidation numbers, as well as a periodic table for reference.
   • Discussion: After the activity, the teacher should lead a classroom discussion where each group shares their strategies for calculating the oxidation number and the difficulties they encountered. The teacher should correct any errors and clarify any doubts.

3. Activity "Oxidation and Reduction Scenario": (5 - 7 minutes)

   • Scenario: The teacher presents the following situation: "You are scientists at a space station on Mars. Recently, you have found a new type of rock that appears to contain a valuable metal. However, before bringing it back to Earth, you need to determine if it undergoes oxidation and reduction reactions in the Martian environment and how this may affect its stability."
   • Task: Each group receives a sample of the "Martian rock" and the task of conducting a simple experiment to determine if it undergoes oxidation and reduction reactions. They should record their observations and, if possible, calculate the oxidation number of the elements in the rock.
   • Materials: The teacher should provide safe and appropriate laboratory materials for the experiment (such as litmus paper, water, vinegar, etc.), as well as guidance on how to conduct the experiment safely.
   • Discussion: After the activity, the teacher should lead a classroom discussion where each group shares their findings and what they have learned about oxidation and reduction reactions in a real-world context. The teacher should correct any errors and clarify any doubts.

Return (10 - 12 minutes)

1. Group Discussion (5 - 6 minutes):

   • The teacher should gather all students and lead a group discussion. Each group should have up to 3 minutes to share their solutions or conclusions from the activities carried out, as well as the strategies they used to reach them.
   • During the presentations, the teacher should encourage students to express their opinions, questions, and doubts. The teacher should listen attentively and take notes to provide constructive feedback and correct any misconceptions that may have arisen during the activities.

2. Connection to Theory (2 - 3 minutes):

   • After all presentations, the teacher should review the activities, highlighting how they connect to the theory of oxidation number. This may include discussing how the observed reactions in the activities relate to oxidation and reduction reactions, and how the oxidation number was used to understand and explain these reactions.
   • The teacher should reinforce the key concepts of the lesson, clarify any misunderstandings, and answer any questions that have not yet been addressed.

3. Individual Reflection (2 - 3 minutes):

   • The teacher should suggest that students take a minute to reflect on what they have learned in the lesson. They should think about the most important concepts they have learned, what questions they still have, and what they thought of the activities.
   • After the minute of reflection, the teacher can ask open-ended questions to stimulate discussion, such as: "What was the most challenging concept of the lesson?" or "What questions have not been answered yet?".
   • The teacher should listen to the students' responses and, if necessary, clarify any misunderstandings or answer any questions that have not yet been addressed.

4. Teacher Feedback (1 minute):

   • To conclude the lesson, the teacher should provide general feedback on the class's participation and performance. The teacher should praise the students' efforts, highlight strengths, and provide constructive suggestions for improvements.
   • The teacher should reinforce the importance of the oxidation number and oxidation and reduction reactions, and how these concepts apply to real-life situations. The teacher may also suggest additional study and practice materials, such as online exercises, explanatory videos, or additional readings.

Conclusion (5 - 7 minutes)

1. Summary of Contents (2 - 3 minutes):

   • The teacher should start the Conclusion by recalling the key concepts covered in the lesson, such as the oxidation number, the rules for assigning it to an element in a compound, and how to identify oxidation and reduction reactions.
   • This can be done interactively by asking students to share what they understood about each concept. This will not only help consolidate learning but also allow the teacher to identify any misunderstandings that may need further clarification.

2. Connection between Theory, Practice, and Applications (1 - 2 minutes):

   • The teacher should then explain how the lesson connected the theory of oxidation number and oxidation and reduction reactions with practice, through the activities carried out.
   • The teacher should emphasize how the problem scenarios and situations proposed in the activities helped illustrate the application of these concepts in the real world, reinforcing the relevance of what was learned.

3. Additional Materials (1 minute):

   • The teacher should suggest additional materials for students who wish to deepen their knowledge of the oxidation number and oxidation and reduction reactions.
   • These materials may include supplementary readings, explanatory videos, online exercises, among others. The teacher should ensure that these materials are accessible and suitable for the students' level of understanding, so they can be useful for their independent study.

4. Relevance of the Subject (1 - 2 minutes):

   • Finally, the teacher should emphasize the importance of the oxidation number and oxidation and reduction reactions in everyday life.
   • The teacher can cite examples of how these concepts are applied in various areas, from food preservation (through oxidation and reduction reactions that occur during the oxidation process) to energy production in batteries (through oxidation and reduction reactions that occur between the battery materials).
   • This will help reinforce the relevance of what was learned and motivate students to continue exploring and applying their knowledge in their daily lives.