Objectives (5 - 7 minutes)

1. Understanding chemical formulas: The main objective of this lesson is for students to become familiar with the notation used in Chemistry to represent substances, that is, chemical formulas. Students should be able to understand the basic structure of a chemical formula and how it is used to represent a specific chemical substance.

2. Differentiation between empirical, molecular, and structural formulas: Students should be able to distinguish between the different types of chemical formulas, including empirical, molecular, and structural formulas. They should understand that each type of chemical formula provides a different level of information about the substance.

3. Practice writing chemical formulas: In addition to understanding chemical formulas, students should be able to write their own chemical formulas. This includes the ability to convert the name of a substance into its corresponding chemical formula and vice versa.

Secondary Objectives:

• Application of chemical formulas in problem-solving: Students should be able to apply their knowledge of chemical formulas to solve practical problems. This may include determining the percent composition of a substance from its chemical formula, or predicting the chemical formula of a compound based on its percent composition.
• Recognition of the importance of chemical formulas in Chemistry: Finally, students should understand the importance of chemical formulas in Chemistry. They should be able to see how chemical formulas are used to represent substances and how they help chemists understand the composition and structure of matter.

Introduction (10 - 15 minutes)

1. Recalling previous concepts: The teacher starts the lesson by recalling basic concepts of Chemistry, such as the structure of the atom, the formation of chemical bonds, and the difference between elements and compounds. This is essential for students to be able to understand and work with chemical formulas. (3 - 5 minutes)

2. Problem-based situations: The teacher proposes two problem-based situations involving the use of chemical formulas. The first one could be: 'Imagine you are a chemist and need to manufacture a new medicine. How would you use chemical formulas to determine the composition of the medicine and how it should be produced?' The second problem-based situation could be: 'You received a sample of an unknown compound. How would you use chemical formulas to determine its identity and properties?' These problem-based situations serve to spark students' interest and demonstrate the relevance of the topic. (5 - 7 minutes)

3. Contextualization: The teacher contextualizes the importance of chemical formulas, explaining that they are used in various areas, such as the pharmaceutical industry, food production, materials manufacturing, and scientific research. The teacher may cite practical examples, such as the chemical formula of water (H2O) and table salt (NaCl), which are widely used in our daily lives. (2 - 3 minutes)

4. Introduction to the topic: Finally, the teacher introduces the topic of the lesson - chemical formulas - in a way that arouses students' curiosity. They may tell the story of how chemical formulas have been developed throughout the history of Chemistry, from Dalton's notation to modern notation. The teacher may also mention curiosities, such as there are more than 100 million known chemical substances, and all of them can be represented by a single chemical formula. (2 - 3 minutes)

Development (20 - 25 minutes)

1. Practical Activity 'Formula Game' (10 - 12 minutes)

   • Activity Description:

     The teacher proposes a playful activity called 'Formula Game'. The goal of the game is for students, divided into teams, to try to guess the chemical formula of a substance based on clues provided by the teacher. The team that guesses the chemical formula first wins the round.

   • Game Preparation:

     Before the lesson, the teacher should prepare cards with the names of various chemical substances and their respective formulas. The cards are shuffled and placed in a pile. In addition, the teacher should prepare a list of clues for each chemical substance, which will be used to guide students in discovering the formula.

   • Game Rules:

     The game starts with the teacher picking the first card from the pile and reading the first clue to the students. If no one guesses, the teacher reads the next clue, and so on, until a team guesses the formula. However, teams can only make one guess per round, and if they are wrong, they must wait for the next round to make another guess.

   • Objective of the Game:

     The goal of the game is for students to practice reading and interpreting chemical formulas, associating them with the names of substances. Additionally, the game helps develop teamwork and the ability to think quickly and creatively.

2. Group Discussion Activity 'Applications of Chemical Formulas' (10 - 12 minutes)

   • Activity Description:

     After the game, the teacher proposes a group discussion activity. Each team receives a list of chemical substances with their respective formulas. The teacher then asks questions, such as: 'What is the importance of this substance for the pharmaceutical industry?', 'How is this substance used in our daily lives?', 'What properties of this substance can be deduced from its chemical formula?'. Teams should discuss the answers among themselves and present them to the class.

   • Activity Objective:

     The objective of this activity is for students to reflect on the practical importance of chemical formulas, understanding that they are not just abstract symbols, but concrete representations of substances with real properties and applications. Additionally, the activity helps develop argumentation, communication, and critical thinking skills.

3. Problem-Solving Activity 'Determining the Chemical Formula' (5 - 7 minutes)

   • Activity Description:

     The teacher proposes a problem for students to solve in groups. The problem consists of determining the chemical formula of an unknown compound from its percent composition. The teacher provides students with the percent composition of the compound in terms of each element it contains. Students should use their knowledge of chemical formulas to solve the problem.

   • Activity Objective:

     This activity aims to consolidate students' understanding of chemical formulas and their practical application. It helps develop problem-solving skills, teamwork, and the application of theoretical concepts.

Feedback (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes)

   • The teacher initiates a group discussion about the solutions or conclusions reached by each team during the activities. Each team has up to 2 minutes to share their strategies and conclusions with the class. The teacher should encourage students to explain the reasoning behind their answers, focusing on the application of chemical formulas.

2. Connection to Theory (2 - 3 minutes)

   • After the discussion, the teacher connects the activities carried out to the theory presented in the lesson. They reinforce the concepts of empirical, molecular, and structural chemical formulas, and how they are used to represent substances and their properties. The teacher may also emphasize the importance of understanding chemical formulas in solving practical problems.

3. Individual Reflection (2 - 3 minutes)

   • The teacher then suggests that students reflect individually on what they learned during the lesson. They ask questions like: 'What was the most important concept you learned today?' and 'What questions have not been answered yet?'. Students have a minute to think about the answers and then are invited to share their reflections with the class. The teacher should listen carefully to students' responses, as they can provide valuable feedback for planning future lessons.

4. Feedback and Closure (1 minute)

   • Finally, the teacher thanks the students for their participation and provides overall feedback on the lesson. They may praise students for their contributions, clarify any points of confusion that arose during the discussion, and encourage students to continue practicing the use of chemical formulas at home. The teacher then concludes the lesson, reminding students about the topic of the next lesson and any homework assignments, if applicable.

Conclusion (5 - 7 minutes)

1. Lesson Summary (2 - 3 minutes)
   • The teacher starts the Conclusion by giving a brief summary of the main points covered in the lesson. They reinforce the concepts of empirical, molecular, and structural chemical formulas, and how they are used to represent substances and their properties. The teacher also reiterates the importance of understanding and being able to write chemical formulas, not only as a theoretical exercise, but also as a practical tool for problem-solving.
2. Connection between Theory, Practice, and Applications (1 - 2 minutes)
   • Next, the teacher highlights how the lesson managed to articulate the theory, practice, and applications of chemical formulas. They recall the activities carried out, such as the 'Formula Game', the discussion on the applications of chemical formulas, and the resolution of practical problems, and show how each of them contributed to the understanding and application of theoretical concepts.
   • The teacher also reinforces the importance of understanding chemical formulas in Chemistry and other related disciplines, such as Biology and Physics. They explain that chemical formulas are a universal language used by scientists from different fields to communicate and understand the composition and properties of matter.
3. Extra Materials (1 minute)
   • The teacher suggests some extra materials for students who wish to deepen their knowledge of chemical formulas. This may include Chemistry books, educational websites, YouTube videos, and interactive learning apps. For example, the teacher may recommend the use of Chemistry simulators that allow students to manipulate atoms and molecules and see how chemical formulas are formed and modified.
4. Importance of the Subject (1 - 2 minutes)
   • Finally, the teacher emphasizes the importance of chemical formulas in everyday life. They may cite examples of how understanding chemical formulas is crucial in various areas, such as: in medicine (to understand the composition and action of medications); in the food industry (to ensure the safety and quality of food); in the chemical industry (for the production of new materials and products); and in the environment (to understand the effects of chemical substances on nature and human health).
   • The teacher may also highlight that the ability to read and write chemical formulas is a valuable skill not only for Chemistry students but for all citizens, as it allows them to understand and discuss issues related to science, technology, and the environment.