Objectives (5 - 7 minutes)

1. Understand and apply concentration units in chemistry, focusing on mass %, volume, and other units.

2. Develop skills to calculate and convert concentration units, using practical examples and real-life applications to facilitate understanding.

3. Promote reflection on the importance of concentration units in daily life and practical applications, such as in the pharmaceutical industry, food preparation, and beverage production.

Secondary Objectives:

• Encourage critical thinking and problem-solving through exercises and problems involving concentration units.

• Foster active student participation, promoting discussions and clarifications of doubts during the lesson.

• Stimulate the connection between theory and practice, emphasizing the importance of the acquired knowledge for understanding and solving everyday situations.

Introduction (10 - 15 minutes)

1. Review of Previous Content: The teacher should start the lesson by briefly reviewing the concepts of concentration and solution that were studied in previous classes. It is important to ensure that students understand these topics as they serve as the basis for the new content to be covered. The teacher can ask questions to verify students' understanding and clarify any doubts that may arise.

2. Problem Situation: To spark students' interest, the teacher can present two problem situations. The first one could be: "How do pharmaceutical industries ensure that the concentration of a medication is precise and uniform in each tablet?" The second one could be: "How do manufacturers of carbonated beverages maintain a constant concentration of carbon dioxide (CO2) in each bottle?" These questions will serve as a starting point for the introduction of the new content.

3. Contextualization: The teacher should explain that concentration units are used not only in laboratories and industries but also in everyday situations. For example, when preparing a recipe, we use the concentration (in %) of an ingredient to determine the necessary amount. Similarly, when diluting a medication, we need to know the concentration to calculate the correct amount.

4. Introduction to the Topic: To introduce the topic in an engaging way, the teacher can share some curiosities. For example, they can mention that Coca-Cola has a secret formula that includes the exact concentration of each ingredient, giving them their characteristic flavor. Another curiosity is that the concentration of salt in seawater is approximately 3.5%, making it unsuitable for human consumption without treatment. These examples can help show students the relevance and applicability of the topic.

5. Gaining Attention: To capture students' attention, the teacher can share the following information: "Did you know that the concentration of oxygen (O2) in the air we breathe is about 21%? This means that, out of every 100 air molecules, 21 are oxygen. Now, imagine if this concentration were higher or lower. How would it affect our health and our environment?" This question can stimulate students' curiosity and prepare them for the exploration of the topic.

Development (20 - 25 minutes)

1. Theory - Concentration Units (Mass %, Volume, and Other Units): (10 - 12 minutes)

   • The teacher should introduce the concentration units, starting with mass %. It should be explained that mass % is the ratio between the solute's mass and the total solution's mass, expressed as a percentage. Practical examples should be used to illustrate this unit, such as the % of salt in a saltwater solution.

   • Next, the teacher should present volume %, which is the ratio between the solute's volume and the total solution's volume, expressed as a percentage. Again, practical examples should be used, such as the % of alcohol in an alcoholic beverage.

   • Finally, the teacher should introduce other concentration units, such as molarity (mol/L), normality (N), parts per million (ppm), and parts per billion (ppb). Each unit should be explained in detail, with practical examples to demonstrate its use.

2. Calculation of Concentration Units: (5 - 7 minutes)

   • The teacher should explain how to calculate concentration units using formulas and equations. It should be emphasized that the calculations depend on the type of concentration unit and that it is important to pay attention to the units during the calculations.

   • The teacher should demonstrate step by step how to make the calculations, using practical examples. Students should be encouraged to follow along with the calculations and ask questions if they have any doubts.

   • After the demonstration, students should be invited to practice the calculations on their own, with the teacher's guidance. The teacher should move around the classroom, offering help and clarifying doubts as needed.

3. Problem Solving: (5 - 6 minutes)

   • The teacher should propose a series of problems involving concentration units for students to solve. The problems should vary in difficulty and address different types of concentration units.

   • Students should be encouraged to work in groups to solve the problems, promoting collaboration and discussion. The teacher should move around the classroom, offering help and clarifying doubts as needed.

   • After solving the problems, the teacher should review the solutions with the class, clarifying any remaining doubts and providing feedback on students' performance.

4. Practical Activity - Dilution Experiment: (5 - 7 minutes)

   • To consolidate learning, the teacher can conduct a simple dilution experiment. In this experiment, the teacher can prepare a stock solution with a known concentration and then ask students to dilute the solution to obtain a desired concentration.

   • Students should be divided into groups, and each group should receive a stock solution and instructions for dilution. They should measure the amount of stock solution and the amount of solvent needed and then calculate the new concentration.

   • After completing the experiment, the results should be discussed in the classroom, reinforcing the connection between theory and practice.

Return (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes): The teacher should facilitate a group discussion on solving the problems and conducting the experiment. Each group should share their conclusions and any difficulties they encountered. The teacher should facilitate the discussion by asking questions to stimulate critical thinking and deepen students' understanding. Some points to be discussed may include:

   • What were the main difficulties encountered when calculating concentration units?

   • How did conducting the experiment contribute to understanding the concepts of concentration and dilution?

   • What are the practical implications of the concepts learned? How do they apply to everyday situations and industries such as pharmaceuticals and food and beverage?

2. Connection with Theory (2 - 3 minutes): The teacher should then make the connection between the group discussion and the theory presented. It should be explained how the theoretical concepts apply to the problems solved and the experiment conducted. The teacher should emphasize the importance of understanding the theory to solve practical problems and apply knowledge in everyday situations. Additionally, the teacher can summarize the main points discussed, reinforcing the most important concepts.

3. Final Reflection (2 - 3 minutes): To conclude the lesson, the teacher should propose that students reflect for a minute on the following questions:

   1. What was the most important concept learned today?

   2. What questions have not been answered yet?

   After the minute of reflection, students should be invited to share their answers. The teacher should listen attentively, offer feedback, and clarify any remaining doubts. This not only helps consolidate learning but also allows the teacher to assess the effectiveness of the lesson and make adjustments as necessary for future classes.

Conclusion (5 - 7 minutes)

1. Summary and Recap of the Lesson: The teacher should start the Conclusion by summarizing the main points covered during the lesson. This includes the definition and importance of concentration units, the difference between mass % and volume %, the introduction of other concentration units, and the practice of calculations and problem-solving. The teacher should ensure that key concepts are reiterated and any remaining doubts are clarified.

2. Connection between Theory, Practice, and Applications: Next, the teacher should emphasize how the lesson connected theory, practice, and applications. It should be highlighted how the theoretical understanding of concentration units allowed for practical problem-solving and the conduct of the dilution experiment. Additionally, the teacher should reiterate the real-world applications of these concepts, such as in the pharmaceutical industry, food preparation, and beverage production.

3. Additional Materials: The teacher can then suggest some reading or viewing materials for students to deepen their understanding of concentration units. This may include chemistry books, educational websites, YouTube videos, or chemistry learning apps. The teacher should encourage students to explore these materials at their own pace and to bring any questions or insights to the next lesson.

4. Importance of the Topic for Everyday Life: Finally, the teacher should emphasize the importance of the topic for everyday life. It should be stressed that concentration units are not just abstract concepts but practical tools that help us understand and control the composition of substances around us. The teacher can reiterate the examples mentioned during the lesson, such as the concentration of salt in a recipe, the concentration of oxygen in the air we breathe, and the concentration of ingredients in medications and beverages. This will help consolidate students' learning and make the topic more relevant and interesting.