Objectives (5 - 7 minutes)

1. Understanding Basic Stoichiometry: The teacher should introduce the concept of stoichiometry, highlighting its importance in the study of Chemistry. Students should understand that stoichiometry is the science that studies the quantitative relationships between reactants and products in a chemical reaction.

2. Calculation of Chemical Reactions: Students should be able to apply stoichiometry concepts to calculate the amount of reactants needed or products formed in a chemical reaction. This includes understanding stoichiometric coefficients and the use of balanced equations.

3. Problem Solving in Stoichiometry: Students should develop skills to solve problems involving stoichiometry. This includes applying formulas and interpreting data in a problem.

Secondary Objectives:

• Development of Critical Thinking: Through solving stoichiometry problems, students should develop critical thinking skills, such as the ability to analyze, synthesize, and evaluate information.

• Encouragement of Curiosity and Autonomous Learning: Students should be encouraged to seek more information about stoichiometry and apply it in everyday situations, thus promoting autonomous learning.

Introduction (10 - 15 minutes)

1. Review of Previous Concepts: The teacher should start the lesson by reviewing the basic concepts of chemical reactions and stoichiometric calculations. This can be done through direct questions to the students or through a brief summary presented by the teacher. It is important to ensure that students have a solid understanding of these concepts before moving on to basic stoichiometry.

2. Presentation of Problem Situations: The teacher should present two problem situations to the students involving stoichiometry. For example, 'If we have x grams of reactant A and y grams of reactant B, how many grams of product C will be formed?' or 'If we have z liters of gas A and w liters of gas B, how many liters of product C will be formed?' These problem situations will serve as a starting point for the exploration of the lesson's theme.

3. Contextualization: The teacher should explain the importance of stoichiometry in various areas, such as the pharmaceutical industry, food production, energy, among others. It should be emphasized that stoichiometry is essential to ensure that chemical reactions occur correctly and to predict the results of these reactions.

4. Capturing Students' Attention: To spark students' interest, the teacher can share some curiosities about stoichiometry. For example, it can be mentioned that stoichiometry is used to determine the amount of fuel needed to launch a rocket into space, or that it is used to calculate the amount of medication to be administered based on the patient's weight. Additionally, it can be shown how stoichiometry is applied in everyday experiments, such as cooking or baking.

5. Introduction of the Topic: Finally, the teacher should introduce the topic of the lesson - basic stoichiometry. It should be explained that basic stoichiometry is the foundation for the study of stoichiometry and that the concepts learned in this lesson will be fundamental for understanding more advanced topics. The teacher can also present the lesson's objective: that students are able to calculate the amount of reactants needed or products formed in a chemical reaction.

Development (20 - 25 minutes)

1. Theory Presentation (8 - 10 minutes):

   • Definition of Stoichiometry: The teacher should start the theory presentation by reinforcing the definition of stoichiometry and its importance. It should be explained that stoichiometry is the science that studies the quantitative relationships between reactants and products in a chemical reaction. It should also be emphasized that stoichiometry is fundamental for predicting and understanding chemical reactions.
   • Balanced Chemical Equations: Next, the teacher should explain the concept of balanced chemical equations. It should be shown how to balance a chemical equation and the importance of this for stoichiometry. Practical examples can be used to illustrate the process of balancing chemical equations.
   • Stoichiometric Coefficients: The teacher should then introduce the concept of stoichiometric coefficients. It should be explained that the stoichiometric coefficients in a chemical equation indicate the proportion in which reactants react and products are formed. It should be shown how to use stoichiometric coefficients to perform stoichiometry calculations.
   • Lavoisier's Law and Proust's Law: The teacher should remind students of the importance of mass conservation in a chemical reaction, citing Lavoisier's and Proust's laws.

2. Resolution of Practical Examples (10 - 12 minutes):

   • Example 1: The teacher should present a practical example of stoichiometry calculation. For example, 'If we have 10 g of reactant A and the balanced chemical equation indicates that the ratio between A and product B is 2:1, how many grams of product B will be formed?' The teacher should guide the students step by step in solving the example, highlighting the importance of correctly using stoichiometric coefficients.
   • Example 2: Next, the teacher should present a more complex example. For example, 'If we have 10 g of reactant A and 20 g of reactant B, and the balanced chemical equation indicates that the ratio between A and B and product C is 1:2:3, how many grams of product C will be formed?' The teacher should again guide the students in solving the example, reminding them to correctly use stoichiometric coefficients and conserve mass.
   • Discussion of Examples: After solving the examples, the teacher should discuss them with the students, clarifying any doubts and highlighting the main points. The importance of understanding and correctly applying stoichiometry concepts should be emphasized.

3. Practical Activity (2 - 3 minutes):

   • Group Activity: To consolidate learning, the teacher should divide the class into groups and propose a practical activity. For example, each group could receive a series of unbalanced chemical equations and would have to balance them and calculate the amount of reactants and products. The teacher can circulate around the room, assisting the groups and clarifying doubts.
   • Feedback and Discussion: After the conclusion of the activity, the teacher should ask each group to share their answers and explain how they arrived at them. A classroom discussion should be promoted, highlighting the strengths of each answer and identifying opportunities for improvement. The teacher should provide constructive feedback and clarify any remaining doubts.

Return (8 - 10 minutes)

1. Review of Contents (3 - 4 minutes):

   • The teacher should start the Return phase by reviewing the main concepts presented during the lesson. A brief review of the definition of stoichiometry, balanced chemical equations, stoichiometric coefficients, and the laws of Lavoisier and Proust should be done.
   • The teacher can reinforce these concepts through direct questions to the students, asking them to explain each concept in their own words. This will help verify students' understanding and identify any areas that may need reinforcement.

2. Connection between Theory, Practice, and Applications (2 - 3 minutes):

   • The teacher should explain how the lesson connected theory (stoichiometry concepts), practice (resolution of examples), and applications (practical activity and discussion of real situations). It should be highlighted how understanding stoichiometry allows predicting and controlling the outcome of a chemical reaction, which is essential in various areas such as industry, medicine, agriculture, among others.
   • The teacher can ask students to share their own insights on this connection. This can help consolidate learning and promote a deeper understanding of the topic.

3. Reflection on Learning (2 - 3 minutes):

   • The teacher should propose that students reflect on what they learned during the lesson. Questions like 'What was the most important concept you learned today?' and 'What questions have not been answered yet?' can be asked.
   • Students should be encouraged to express their reflections openly and honestly. The teacher should listen carefully to students' responses and respond constructively, clarifying any remaining doubts and reinforcing the main points of the lesson's topic.

4. Feedback and Evaluation (1 minute):

   • The teacher should end the lesson by asking students to evaluate the lesson. Questions like 'What did you think of today's lesson?' and 'Is there anything you would like to be different next time?' can be asked.
   • Students' feedback can help the teacher improve their future lessons and adapt their teaching to meet students' needs and preferences.

Conclusion (5 - 7 minutes)

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

   • The teacher should start the Conclusion by summarizing the main points of the lesson. It should be reinforced that stoichiometry is the science that studies the quantitative relationships between reactants and products in a chemical reaction, and that for this, the use of balanced chemical equations and stoichiometric coefficients is fundamental.
   • The importance of mass conservation in a chemical reaction should be recalled, citing Lavoisier's and Proust's laws.
   • The teacher should also highlight the importance of practice in understanding stoichiometry, reinforcing the importance of solving examples and the proposed practical activity.

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

   • The teacher should emphasize how the lesson connected theory, practice, and applications. It should be reinforced that understanding stoichiometry allows predicting and controlling the outcome of a chemical reaction, which is essential in various areas such as industry, medicine, agriculture, among others.

3. Complementary Materials (1 minute):

   • The teacher should suggest complementary materials for students who wish to deepen their knowledge of stoichiometry. Books, websites, videos, and apps that present stoichiometry concepts interactively and playfully, allowing students to practice problem-solving, can be suggested.

4. Applications in Everyday Life (1 - 2 minutes):

   • To conclude, the teacher should highlight how stoichiometry is applied in everyday life. Examples such as using stoichiometry to calculate the amount of ingredients needed in a recipe, to predict the outcome of a chemical reaction in a home experiment, or to determine the amount of medication to be administered based on the patient's weight can be mentioned.
   • The teacher should emphasize that stoichiometry is not just an abstract concept studied in school, but a powerful tool that can be used in various real-life situations.