Lesson Plan | Traditional Methodology | Chemical Formulas

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to clearly establish the educational objectives that will be achieved during the class, providing students with a clear understanding of what is expected of them. This stage also guides the teacher on the key points to be addressed, ensuring that all essential aspects of the topic are covered in an organized and efficient manner.

Main Objectives

1. Empower students to identify and write the chemical formulas of two main compounds based on their constituent elements.

2. Teach students to differentiate the various ways of representing a chemical formula, such as empirical, molecular, and structural formulas.

Introduction

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to capture students' attention and provide an initial context that makes the topic of Chemical Formulas more accessible and engaging. By presenting everyday examples and curiosities, students can perceive the practical application of what they will learn, increasing engagement and motivation for the class. Furthermore, this introduction sets the stage for the more technical concepts that will be addressed later.

Context

To start the class on Chemical Formulas, it is important to contextualize the relevance of this topic in everyday life and in science. Chemical formulas are symbolic representations that describe the composition of chemical substances using the symbols of chemical elements. They are fundamental for understanding chemical reactions, properties of substances, and for precise communication in the field of Chemistry. The ability to interpret and write chemical formulas is essential for any Chemistry student, as they form the basis for the study of compounds and their interactions.

Curiosities

Did you know that the chemical formula of common sugar we use everyday is C12H22O11? Moreover, water, which is essential for life, has a very simple formula: H2O. These representations show us the exact ratio of atoms of each element present in the substance, which is crucial for understanding its properties and behaviors.

Development

Duration: (45 - 55 minutes)

The purpose of this stage of the lesson plan is to provide a detailed and practical understanding of the different ways of representing chemical formulas. By addressing specific and essential topics, along with proposing questions for resolution in class, students will have the opportunity to apply the knowledge acquired in a practical and interactive manner. This approach helps solidify theoretical understanding through targeted examples and exercises.

Covered Topics

1. Empirical Formulas: Explain that the empirical formula is the simplest representation of the ratio between the elements of a compound. Example: The empirical formula of hydrogen peroxide (H₂O₂) is HO, showing the simplest ratio of hydrogen to oxygen atoms. 2. Molecular Formulas: Detail that the molecular formula indicates the actual number of atoms of each element in a molecule of compound. Example: The molecular formula of glucose is C₆H₁₂O₆, representing six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. 3. Structural Formulas: Explain that structural formulas show how the atoms in a molecule are bonded together. Example: The structural formula of ethane (C₂H₆) reveals the arrangement of atoms relative to each other, showing the bonds between the carbon and hydrogen atoms. 4. Understanding Ionic Formulas: Discuss the formation of ionic compounds, explaining how they are represented. Example: Sodium chloride (NaCl) is formed by the combination of Na⁺ and Cl⁻ ions. 5. Analysis of Common Compounds: Discuss the composition of common compounds and their representation. Example: Water (H₂O) and carbon dioxide (CO₂) are examples that help illustrate the difference between empirical and molecular formulas.

Classroom Questions

1. What is the empirical formula of the compound C₆H₁₂O₆? 2. Write the molecular formula of the compound whose empirical formula is CH₂O and whose molar mass is 180 g/mol. 3. Draw the structural formula of methane (CH₄) and explain the arrangement of the atoms.

Questions Discussion

Duration: (20 - 25 minutes)

The purpose of this stage of the lesson plan is to consolidate learning, allowing students to review and discuss the answers to the proposed questions, promoting a deeper and more critical understanding of the content. Through guided discussion and engagement with reflective questions, students can clarify doubts and reinforce the concepts learned, ensuring a more effective assimilation of the topic addressed.

Discussion

•  Discussion of the Questions:

• What is the empirical formula of the compound C₆H₁₂O₆?

• • The empirical formula of the compound C₆H₁₂O₆ is CH₂O. This is because the empirical formula is the simplest ratio between the elements in the compound. By dividing the subscripts by 6 (the greatest common divisor), we obtain CH₂O.

• Write the molecular formula of the compound whose empirical formula is CH₂O and whose molar mass is 180 g/mol.

• • First, we calculate the molar mass of the empirical formula CH₂O: C (12 g/mol) + H₂ (2 g/mol) + O (16 g/mol) = 30 g/mol. Knowing that the molar mass of the compound is 180 g/mol, we divide 180 g/mol by 30 g/mol, resulting in 6. Multiplying the empirical formula by 6, we get C₆H₁₂O₆.

• Draw the structural formula of methane (CH₄) and explain the arrangement of the atoms.

• • The structural formula of methane (CH₄) shows a central carbon atom bonded to four hydrogen atoms. Each C-H bond is a single bond (a pair of shared electrons). This results in a tetrahedral structure, where the bond angles are approximately 109.5°.

Student Engagement

1. 樂 Questions and Reflections to Engage Students: 2. Why is it important to understand the difference between empirical and molecular formulas? 3. How do chemical formulas help us understand the properties and behaviors of substances? 4. Can you think of an everyday example where a small mistake in the chemical formula could have a big impact? 5. Group discussion: Discuss how the structural representation of compounds can influence the understanding of chemical reactions. 6. How can the chemical formula of a compound take on different forms of representation (empirical, molecular, and structural), and what are the advantages and disadvantages of each?

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to summarize and reinforce the main points addressed during the class, ensuring that students have a clear and consolidated understanding of the content. Additionally, this stage allows students to connect theory with their practical applications, reinforcing the relevance of the topic to their daily lives and future studies.

Summary

• Explanation of empirical, molecular, and structural formulas.
• Demonstration of how to find the empirical and molecular formula of compounds.
• Discussion on the representation of ionic compounds.
• Detailed analysis of common compounds such as water (H₂O) and carbon dioxide (CO₂).
• Resolution of practical problems and examples of chemical formulas.

The class connected theory with practice by using everyday examples, such as the formula for water and sugar, and by solving practical problems that allowed students to apply theoretical knowledge. Through guided activities and discussion of questions, students were able to see how chemical formulas are used to describe the composition and properties of substances in real-life situations.

Understanding chemical formulas is essential not only for the study of Chemistry but also for understanding many phenomena in everyday life. For example, knowing the formula of water (H₂O) helps us understand why it is vital for life. Moreover, recognizing the difference between empirical and molecular formulas can be crucial in industrial contexts, such as in drug manufacturing, where precision in formulation is fundamental.