Objectives (5 - 10 minutes)

1. Understanding of Stoichiometry: Students should be able to understand the concept of stoichiometry, which is the numerical relationship between reactants and products in a chemical reaction. They should be able to apply this concept to calculate quantities of reactants and products in a reaction.

2. Calculation of Purity: Students should be able to calculate the purity of a substance, understanding that purity is the relationship between the amount of pure substance and the total amount, including impurities. They should be able to apply this skill in practical situations.

3. Calculation of Yield: Students should be able to calculate the yield of a chemical reaction, which is the relationship between the amount of product obtained and the theoretically maximum possible amount. They should understand the importance of yield in the chemical industry and be able to apply this concept in calculations.

Secondary Objectives:

• Development of problem-solving skills: In addition to the main Objectives, the lesson should help students develop their problem-solving skills, which are crucial in the discipline of chemistry and in many other areas of life.

• Promote understanding of the importance of chemistry in everyday life: The lesson should take the opportunity to highlight examples of how these concepts are applied in everyday life, helping students to see the relevance of chemistry in their lives.

Introduction (10 - 15 minutes)

1. Recalling previous concepts: The teacher should start the lesson by recalling the basic concepts of chemical reactions and chemical equations that were previously studied by the students. This can be done interactively, through questions and answers, or through a brief theoretical review. This step is important to ensure that students have a solid foundation to understand the new concepts that will be presented.

2. Problem situations: The teacher should then present two problem situations that will be addressed during the lesson. The first one could be: 'If you have a reagent of known purity and need to calculate the amount of product that can be obtained, how would you do that?' The second situation could be: 'If you have a reagent of unknown purity and need to calculate the amount of product that can be obtained, how would you do that?' These questions should serve to arouse the interest of the students and prepare them for the content that will be presented.

3. Contextualization: The teacher should then contextualize the importance of stoichiometry, purity, and yield in the chemical industry and in everyday life. For example, it can be mentioned how purity and yield are critical factors in the production of medicines, food, and other chemical products. In addition, it can be mentioned how these concepts are applied in everyday situations, such as calculating the amount of ingredients needed for a recipe or determining the efficiency of a fuel.

4. Introduction of the topic: To arouse the interest of the students, the teacher can introduce the topic with some curiosities or interesting applications. For example, it can be mentioned how stoichiometry was used to determine the chemical composition of distant stars. In addition, it can be mentioned how purity and yield are critical factors in the production of recreational drugs, such as cocaine. However, it is important to address this topic with sensitivity and ensure that the discussion is appropriate for the age group and the school environment.

Development (20 - 25 minutes)

1. Theory - Purity Concept (5 - 7 minutes):

   • The teacher should start by explaining what the purity of a substance is and how it is calculated. Purity, in this context, refers to the amount of pure substance in a sample, excluding impurities.

   • It should be emphasized that purity is expressed as a percentage, with 100% being the maximum purity.

   • The teacher should present the formula for calculating purity:

     Purity (%) = (Mass of pure substance / Mass of sample) x 100

   • Practical examples should be used to illustrate the calculation of purity. For example, the teacher can present a sample of a substance of known purity and ask the students to calculate the purity.

2. Theory - Yield Concept (5 - 7 minutes):

   • The teacher should then explain what the yield of a reaction is and how it is calculated. Yield is the relationship between the amount of product obtained and the theoretically maximum possible amount.

   • It should be emphasized that yield is expressed as a percentage, with 100% being the maximum theoretical yield.

   • The teacher should present the formula for calculating yield:

     Yield (%) = (Actual quantity of product / Theoretical maximum quantity) x 100

   • Practical examples should be used to illustrate the calculation of yield. For example, the teacher can present a chemical reaction and ask the students to calculate the yield.

3. Application - Purity and Yield Exercises (10 - 12 minutes):

   • The teacher should then present a series of practical exercises involving the calculation of purity and yield. These exercises should vary in difficulty, starting with simple problems and gradually increasing in complexity.
   • Students should be encouraged to work in groups to solve the exercises, promoting collaboration and discussion among them. The teacher should circulate around the room, providing guidance and clarifying doubts as necessary.
   • After solving the exercises, the teacher should review the answers with the class, ensuring that the students understand the concepts and know how to apply them correctly.

4. Review - Recapitulation and Connection with Theory (5 - 7 minutes):

   • To conclude the Development part, the teacher should conduct a review of the concepts presented, reinforcing the importance of stoichiometry, purity, and yield in chemistry and everyday life.
   • The teacher should make connections between theory and practical exercises, highlighting how the concepts were applied to solve the problems.
   • Students should be encouraged to ask questions and clarify any doubts they may have. The teacher should ensure that all students have a clear understanding of the concepts before moving on to the next part of the lesson.

Return (10 - 15 minutes)

1. Group Discussion (5 - 7 minutes):

   • The teacher should divide the class into groups and ask each group to discuss and share their solutions to the purity and yield exercises.
   • Each group should be encouraged to present their solutions to the class, explaining the process they used to arrive at the answer.
   • The teacher should facilitate the discussion by asking questions to stimulate critical thinking and students' understanding.
   • This step is important to promote collaboration among students, allowing them to learn from each other and develop their communication and argumentation skills.

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

   • After the group presentations, the teacher should make the connection between the solutions presented and the theoretical concepts discussed in the lesson.
   • The teacher should highlight how the calculations of purity and yield were applied in practical situations, reinforcing the relevance and applicability of the concepts.
   • This step is important to consolidate students' learning and ensure that they are able to apply the concepts in different contexts.

3. Individual Reflection (3 - 5 minutes):

   • The teacher should propose that students reflect individually on what they learned in the lesson.
   • To facilitate reflection, the teacher should ask questions such as: 'What was the most important concept you learned today?' and 'What questions have not been answered yet?'.
   • Students should be encouraged to write down their answers, which can be shared with the class or handed to the teacher after the lesson.

4. Feedback and Clarification of Doubts (1 - 2 minutes):

   • Finally, the teacher should ask for feedback from students about the lesson, asking if they found the explanation clear and if they feel comfortable with the concepts presented.
   • The teacher should also invite students to express any doubts or difficulties they may still have, ensuring that all concepts were understood.
   • Students' feedback can be used to adjust the planning of future lessons and ensure that individual learning needs are met.

Conclusion (5 - 7 minutes)

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

   • The teacher should start the Conclusion of the lesson by recalling the main concepts that were addressed during the lesson: the calculation of purity and yield, and their importance in chemistry and everyday life.
   • The definition of purity and yield should be emphasized, as well as the formula for calculating each one.
   • The teacher can give a brief recap of the practical examples that were used to illustrate these concepts, reinforcing their application in real situations.

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

   • The teacher should then explain how the lesson connected theory, practice, and applications.
   • It should be emphasized how the theoretical concepts of purity and yield were applied in practice, through the calculation exercises.
   • Furthermore, the relevance of these concepts should be reinforced, explaining again how they are applied in the chemical industry and in everyday life.

3. Extra Materials (1 - 2 minutes):

   • The teacher should suggest some extra materials for students who wish to deepen their knowledge on the subject.
   • These materials may include chemistry books, educational websites, explanatory videos, and additional exercises.
   • The teacher can also indicate some simple experiments that students can perform at home to reinforce the concepts learned.

4. Importance of the Subject (1 minute):

   • To conclude, the teacher should emphasize the importance of the concepts learned for students' lives.
   • It should be remembered that chemistry is present in our daily lives, from the production of food and medicines to the generation of energy.
   • The teacher can give examples of how stoichiometry, purity, and yield are applied in everyday situations, such as calculating the amount of ingredients for a recipe or the efficiency of a fuel.

This Conclusion moment is important to consolidate students' learning, reinforce the relevance of the concepts presented, and motivate them to continue studying the subject.