Objectives (5 - 10 minutes)

1. Understanding Chemical Formulas: The main objective of this lesson is to ensure that students fully understand what chemical formulas are, how they are formed, and how they should be interpreted. This includes the ability to read chemical formulas and identify the elements and the proportion of atoms in them.

2. Writing and Interpreting Chemical Formulas: In addition to simply reading chemical formulas, the lesson should focus on helping students develop the skills necessary to write their own chemical formulas. This includes understanding the basic rules for writing chemical formulas and the ability to interpret formulas written by others.

3. Practical Application of Chemical Formulas: Finally, students should be able to apply the knowledge gained in practical situations. This may include solving problems involving determining the proportion of atoms in a substance from its chemical formula, or determining the chemical formula of a substance from its composition.

Secondary Objectives:

• Stimulate critical thinking and problem-solving skills of students through practical and interactive activities.
• Foster collaboration among students through group activities.
• Develop students' communication skills through classroom discussions and presentations.

Introduction (10 - 15 minutes)

1. Review of Previous Content: The teacher should start the lesson by briefly reviewing the concepts of atoms, elements, and chemical compounds. This can be done through quick questions or a brief summary. It is important to ensure that students have a solid understanding of these concepts before moving on to chemical formulas.

2. Problem Situation: The teacher can present two problem situations to arouse the interest of the students. The first one could be: 'Imagine you have an unknown substance. How could you determine the composition of this substance?'. The second one could be: 'Imagine you have the chemical formula of a substance, but you don't know what the substance is. How could you determine what the substance is from the chemical formula?'.

3. Contextualization: The teacher should then contextualize the importance of chemical formulas, explaining that they are the language of chemistry and are used to represent and describe the composition and structure of substances. The teacher can give examples of how chemical formulas are used in everyday life, such as in the pharmaceutical industry, food production, energy production, etc.

4. Introduction of the Topic: To introduce the topic of chemical formulas, the teacher can share some curiosities. For example, they can mention that the chemical formula of water (H2O) is one of the most well-known and important formulas in chemistry, or they can mention that the chemical formula of diamond (C) is composed of only one element, but diamond is one of the most valuable and difficult-to-find substances on Earth.

5. Generating Interest: Finally, the teacher can share some interesting applications of chemical formulas. For example, they can mention that scientists use chemical formulas to design new drugs, or they can mention that chemical formulas are used to describe chemical reactions that occur in the human body, nature, and industry. This can help spark students' interest and show the relevance and importance of the topic.

Development (20 - 25 minutes)

1. Activity 'Building Formulas' (10 - 15 minutes): This playful and practical activity involves students in constructing their own chemical formulas. The teacher should provide cards with symbols of chemical elements and numbers to represent the quantity of each element in the formula. The students, divided into groups, receive a set of cards and must use them to create chemical formulas for different compounds. The teacher should guide the students to follow the rules for writing chemical formulas, such as using subscripts to indicate the quantity of atoms of each element. After constructing the formulas, each group should present their formulas to the class and explain how they arrived at them. The teacher should correct and provide feedback to the groups, reinforcing the concepts of chemical formulas and the importance of the proportion of atoms.

   • Step by Step:
     1. The teacher divides the class into groups and provides each group with a set of cards with symbols of chemical elements and numbers.
     2. The students, within each group, should discuss and decide which cards they will use to form their chemical formulas.
     3. After constructing the formulas, each group should present their formulas to the class and explain how they arrived at them.
     4. The teacher should correct and provide feedback to the groups, reinforcing the concepts of chemical formulas and the importance of the proportion of atoms.

2. Activity 'Deciphering Formulas' (10 - 15 minutes): In this activity, students are challenged to decipher chemical formulas to discover the name of the substances. The teacher should provide a list of chemical formulas and a periodic table. The students, again divided into groups, should use the periodic table to identify the elements present in each formula and then combine the symbols of the elements to form the name of the substance. The teacher should guide the students to use parentheses and subscripts to interpret the formulas. At the end of the activity, each group should present their answers to the class, and the teacher should correct and provide feedback to the groups.

   • Step by Step:
     1. The teacher provides each group with a list of chemical formulas and a periodic table.
     2. The students, within each group, should use the periodic table to identify the elements present in each formula and then combine the symbols of the elements to form the name of the substance.
     3. After decoding the formulas, each group should present their answers to the class, and the teacher should correct and provide feedback to the groups.

3. Discussion and Reflection (5 - 10 minutes): After the conclusion of the activities, the teacher should promote a classroom discussion to reflect on what was learned. The teacher should ask open-ended questions to stimulate students' reflection, such as: 'What was the most challenging part of the activities? Why?', 'How do you think you can apply what you learned today in real situations?'. The teacher should encourage all students to participate in the discussion, ensuring that everyone has the opportunity to express their opinions and doubts.

   • Step by Step:
     1. The teacher promotes a classroom discussion to reflect on what was learned.
     2. The teacher asks open-ended questions to stimulate students' reflection and encourages all students to participate in the discussion.

Return (10 - 15 minutes)

1. Group Review (5 - 7 minutes): The teacher should conduct a group review, where each team will briefly present their conclusions and solutions found during the activities. The teacher should ask students to explain the process they used to build their chemical formulas and decipher the provided formulas. During the presentations, the teacher should ask questions to stimulate reflection and deepen students' understanding.

   • Step by Step:
     1. The teacher requests each group to briefly present their conclusions and solutions found during the activities.
     2. During the presentations, the teacher asks questions to stimulate reflection and deepen students' understanding.

2. Connection with Theory (2 - 3 minutes): After the presentations, the teacher should provide a brief recap of the theoretical concepts covered in the lesson and connect them with the practical activities carried out. The teacher can highlight how understanding chemical formulas is fundamental to chemistry, and how the practical application of these concepts can help solve everyday problems.

   • Step by Step:
     1. The teacher provides a brief recap of the theoretical concepts covered in the lesson.
     2. The teacher connects the theoretical concepts with the practical activities carried out.

3. Individual Reflection (3 - 5 minutes): The teacher should propose that students reflect individually on what they learned in the lesson. The teacher can ask questions such as: 'What was the most important concept you learned today?', 'What questions have not been answered yet?', 'How can you apply what you learned today in other situations?'. The teacher should encourage students to write down their reflections and bring their doubts to the next lesson.

   • Step by Step:
     1. The teacher proposes that students reflect individually on what they learned in the lesson.
     2. The teacher asks questions to stimulate students' reflection and encourages them to write down their reflections and doubts.

4. Teacher's Feedback (1 - 2 minutes): Finally, the teacher should give overall feedback on the lesson, praising the students' achievements, highlighting strengths and areas that need improvement. The teacher should encourage students to continue studying and practicing the concepts learned, and reinforce that they are available to clarify any doubts that may arise.

   • Step by Step:
     1. The teacher gives overall feedback on the lesson.
     2. The teacher encourages students to continue studying and practicing the concepts learned, and reinforces that they are available to clarify any doubts that may arise.

Conclusion (5 - 10 minutes)

1. Summary of Contents (2 - 3 minutes): The teacher should recap the main points covered during the lesson, reinforcing the definition of chemical formulas, the rules for writing and reading chemical formulas, and the importance of the proportion of atoms in the chemical formula of a substance. The teacher can use practical examples to illustrate these concepts and can review the correct answers from the activities carried out.

   • Step by Step:
     1. The teacher recaps the main points covered during the lesson.
     2. The teacher reinforces the importance of the proportion of atoms in the chemical formula of a substance.

2. Theory-Practice Connection (1 - 2 minutes): The teacher should highlight how the lesson connected theory, practice, and real-world applications. The teacher can mention the practical activities carried out and how they helped students apply theoretical concepts, develop problem-solving skills, and understand the importance of chemical formulas in chemistry and other areas.

   • Step by Step:
     1. The teacher highlights how the lesson connected theory, practice, and real-world applications.

3. Extra Materials (1 - 2 minutes): The teacher should suggest extra materials for students who wish to deepen their understanding of the topic. These materials may include books, websites, videos, and chemistry apps. For example, the teacher can recommend a video that visually and interactively explains how to write and interpret chemical formulas, or a chemistry app that allows students to practice writing and interpreting chemical formulas.

   • Step by Step:
     1. The teacher suggests extra materials for students who wish to deepen their understanding of the topic.

4. Topic Relevance (1 - 2 minutes): Finally, the teacher should emphasize the importance of the topic for students' lives. The teacher can explain that understanding chemical formulas is fundamental to chemistry, a science that is present in many aspects of our daily lives, such as food production, health, energy, and the environment. Additionally, the teacher can mention that the problem-solving and critical thinking skills developed during the lesson are valuable skills that students can apply in other subjects and situations.

   • Step by Step:
     1. The teacher emphasizes the importance of the topic for students' lives.
     2. The teacher mentions that the skills developed during the lesson are valuable skills that students can apply in other subjects and situations.