Lesson Plan | Active Learning | Proust's Law of Definite Proportions

Assumptions: This Active Lesson Plan assumes: a 100-minute class, prior student study with both the Book and the start of Project development, and that only one activity (among the three suggested) will be chosen to be conducted during the class, as each activity is designed to take up a significant portion of the available time.

Objectives

Duration: (5 - 10 minutes)

This stage of the lesson plan is crucial to establish a solid foundation of understanding regarding Proust's law. By clearly outlining the main objectives, students will be guided on what is expected of them to comprehend and apply. This not only facilitates content absorption but also directs students' focus to the most essential aspects of the theme, preparing them for the practical activities that will follow.

Main Objectives:

1. Ensure that students understand the fundamental principles of Proust's law, which states that a compound substance is always formed by components in fixed proportions by mass.

2. Empower students to apply Proust's law in different practical and theoretical contexts, including the calculation and experimental verification of stoichiometric proportions in chemical reactions.

Side Objectives:

1. Develop logical and critical reasoning skills in students when analyzing and discussing cases where Proust's law applies or not.
2. Encourage curiosity and scientific investigation through historical examples and simple experiments that illustrate the importance of stoichiometric proportion.

Introduction

Duration: (15 - 20 minutes)

The introduction serves to engage students and connect prior knowledge with the lesson's theme. The proposed problem situations encourage students to think critically and apply the concept of fixed proportions in practical contexts, preparing them for interactive activities in class. The contextualization, on the other hand, highlights the historical and practical relevance of Proust's law, increasing students' interest in the topic and showing how theoretical learning relates to real and past situations.

Problem-Based Situations

1. Imagine a chef needs to prepare a recipe and the available ingredients are in random quantities. How could he use Proust's law to ensure that the final recipe is consistent, considering the fixed proportion of the components?

2. In a laboratory, students receive a task to determine the composition of an unknown sample that supposedly contains iron oxide. They have iron oxide and sodium hydroxide available. How could Proust's law help them identify the presence of iron oxide and the exact proportion of the elements?

Contextualization

Proust's law, also known as the Law of Definite Proportions, is not merely a theoretical concept; it has extensive practical applications in various fields, from cooking to forensic chemistry. For example, in forensic medicine, analyzing substances in biological samples can help determine the presence of drugs or poisons, based on the fixed proportion of the elements that make up these substances. Furthermore, the historical context of Proust's law discovery by Joseph Proust in 1799 during his investigations into the composition of silver carbonate shows how curiosity and meticulousness are essential for scientific advancement.

Development

Duration: (75 - 85 minutes)

The Development section is designed to allow students to practically and playfully apply the concepts of stoichiometric proportions from Proust's law. By participating in one of the proposed activities, students can consolidate their knowledge through solving real problems and hypothetical scenarios, stimulating critical thinking and teamwork. This practical approach not only solidifies theoretical understanding but also demonstrates the relevance and versatility of the concept in different contexts, preparing students for future explorations in chemistry and related sciences.

Activity Suggestions

It is recommended to carry out only one of the suggested activities

Activity 1 - The Mystery of the Potions in the Kitchen

> Duration: (60 - 70 minutes)

- Objective: Apply Proust's law to solve a practical problem and understand how stoichiometric proportions affect the outcome of a reaction or, in this case, a recipe.

- Description: Students are divided into groups and each group is tasked with solving a 'mystery'. They need to help a chef whose secret recipes are being altered by a mysterious enemy who swaps the ingredients but keeps the total mass constant. Each ingredient is replaced by another that maintains the fixed proportion established by Proust's law. Students must identify the original ingredients of the recipes based on stoichiometric proportions.

- Instructions:

• 1. Distribute materials: 'altered' ingredients, list of original recipes, scales, and basic kitchen utensils.
• 2. Ask each group to analyze the proportions of the new ingredients and compare them with the list of original recipes.
• 3. Students should calculate the stoichiometric proportions of the provided ingredients and compare them with the ideal proportions of the recipes.
• 4. Each group will present their findings and which ingredients they believe were used in the original recipes, justifying based on the calculated proportions.
• 5. Conduct a class discussion about how Proust's law was applied and what they learned about fixed proportions.

Activity 2 - Stereo Cinema: An Adventure in Proportions

> Duration: (60 - 70 minutes)

- Objective: Understand the importance of stoichiometric proportions and how they apply in artistic and practical contexts, such as setting creation.

- Description: In this activity, student groups assume the role of film producers who need to create a movie where the proportion of scenes and characters is crucial to the plot. They must use Proust's law to ensure that the scenes are assembled correctly, considering the fixed proportions of each element in the setting and characters.

- Instructions:

• 1. Divide the class into groups of up to 5 students and provide each group with a scene description that includes characters and elements of the setting.
• 2. Each group must use Proust's law to calculate the proportions of the elements in each scene.
• 3. After the calculations, students should create a model or drawing that represents the scene using the calculated proportions.
• 4. Each group will present their model and explain how they applied Proust's law to create the scene.
• 5. Conclude with a discussion about how proportions affect visual perception and harmony in a film scene.

Activity 3 - The Great Challenge of Mysterious Proportions

> Duration: (60 - 70 minutes)

- Objective: Develop analysis and application skills of Proust's law in a practical laboratory context, reinforcing the understanding of stoichiometric proportions.

- Description: Students are challenged to solve an enigma where they need to discover the composition of an unknown substance that matches a pattern of fixed proportions. Using simple chemical reactions, they must identify the elements present in the substance and their proportions, applying Proust's law.

- Instructions:

• 1. Organize the class into groups and distribute reagent kits that include substances that react with each other.
• 2. Each group receives a description of the unknown substance and must plan a series of tests to identify the elements and their proportions.
• 3. Students carry out the reactions, observe the results, and use the data to calculate the proportions of the elements.
• 4. Each group will present their results and the process used to reach conclusions, discussing the difficulties encountered and how Proust's law was applied.
• 5. Conclude with a reflection on the importance of stoichiometric proportions in chemistry and in practical applications.

Feedback

Duration: (10 - 15 minutes)

This stage of the lesson plan is essential for consolidating student learning, allowing them to reflect on the practical activities and share their findings with peers. Group discussions help reinforce the understanding of Proust's law concepts, as well as promote communication and collaboration skills. Students will also recognize the applicability of chemical concepts in everyday situations and in other areas of knowledge.

Group Discussion

At the end of the practical activities, gather all students for a group discussion. Start the discussion with a brief introduction, explaining that the purpose is to share discoveries and challenges faced during the activities and how Proust's law was applied in such diverse contexts. Encourage each group to present a summary of their experience, highlighting the main lessons learned and the solutions found.

Key Questions

1. What were the biggest challenges in applying Proust's law in the activities carried out?

2. How did the understanding of stoichiometric proportions influence the resolution of the proposed problems?

3. Can you cite examples of how Proust's law could be applied in everyday situations or in other subjects?

Conclusion

Duration: (5 - 10 minutes)

The conclusion stage aims to consolidate learning, ensuring that students have captured the central concepts of the lesson. Furthermore, it aims to clarify how the presented theory applies in practice and in different contexts, reinforcing the importance of studying chemistry. This moment also serves to clarify any remaining doubts and to wrap up the lesson in a clear and integrated manner.

Summary

In concluding the lesson, the teacher should summarize the main points covered about Proust's Law, emphasizing that compound substances are formed by elements in fixed and constant proportions. It should be reiterated how this understanding is fundamental to chemistry, allowing predictions of reaction outcomes and understanding the formation of different compounds.

Theory Connection

The teacher should explain how today's lesson connected theory with practice, highlighting that the activities performed allowed students to apply the theoretical concepts of Proust's law in practical situations, such as in forensic chemistry, cooking, and laboratory experiments. This approach demonstrates the relevance of chemical concepts in everyday life and in other subjects.

Closing

Finally, the teacher should discuss the importance of Proust's Law in scientific and technological development, exemplifying how understanding stoichiometric proportions is crucial for various applications, from drug manufacturing to the development of new materials. This contextualization helps reinforce the relevance of the study of chemistry for students.