Context

Friedrich August Kekulé von Stradonitz was a German chemist who made significant contributions to the understanding of organic chemistry. In his time, chemistry was far from being the organized science we know today. Organic chemistry, in particular, was a whirlwind of mysteries and assumptions. It was when Kekulé postulated two revolutionary ideas that became the cornerstones for the study of organic chemistry: The tetravalence of the carbon atom and the formation of carbon chains.

The first of these postulates, the tetravalence of carbon, proposes that each carbon atom forms four covalent bonds to achieve a stable configuration. This concept provided the basis for understanding how atoms bond to form complex molecules in organic compounds. The second postulate, the formation of carbon chains, suggests that carbon atoms can bond in long chains, paving the way for the existence of a multitude of organic compounds.

These postulates by Kekulé are not just abstract theories but also have huge practical implications. The tetravalence of carbon is the guiding principle in building large molecules, such as the proteins found in biological life. Carbon chains are the backbone of the entire field of petrochemistry, which produces fuels, plastics, and a multitude of other materials important in our daily lives.

To understand the importance of Kekulé's postulates, one just needs to look around. The plastics we use, the fabrics of our clothes, the medicines we take, and the food we consume - all are based on organic compounds. Understanding the fundamental principles of organic chemistry, such as Kekulé's postulates, is essential to understand how the world around us works and how we can continue to develop new technologies and improve the quality of life.

The following resources can be used to learn and delve deeper into Kekulé's postulates:

1. Kekulé's Postulates - Brasil Escola
2. Kekulé's Postulates - Mundo Educação
3. Kekulé and Organic Chemistry - SóQ

Practical Activity: "Building the World of Organic Chemistry: Kekulé's Contributions"

Project Objective:

The project aims to promote a deep and practical understanding of Kekulé's postulates - the tetravalence of carbon and the formation of carbon chains.

Detailed Project Description:

Students, in groups of 3 to 5, will actually "build" molecular structures of organic compounds using molecular modeling kits. They will explore and identify the tetravalence of carbon and the formation of carbon chains in various compounds. Additionally, they will research and present how such structures and compounds correlate with practical applications in our daily lives.

Materials Needed:

1. Molecular modeling kits
2. Internet access for research

Detailed Step-by-Step for Activity Execution:

1. Form groups of 3 to 5 students. Each group will receive a molecular modeling kit.
2. Each group should research and choose 10 distinct organic compounds. They should ensure to choose compounds that vary in complexity and demonstrate the tetravalence of carbon and the formation of carbon chains.
3. Using the molecular modeling kit, the groups should assemble the molecular structures of the compounds they chose. They should focus on visualizing the tetravalence of carbon and the formation of carbon chains.
4. Once the molecular structures are ready, the groups should photograph each model individually.
5. Next, the groups should research and identify, for each compound, a practical application or everyday object in which such compound is found or has relevant use.
6. After the research, the groups will prepare a presentation, using the photos of the molecular models and highlighting the practical applications of the chosen compounds.

Project Deliverables:

The project will be delivered in two parts:

1. In-Class Presentation: Each group will present the molecular models they built and explain their research on the practical applications of the compounds. The presentations should be well-documented and explanatory, clearly demonstrating the understanding of Kekulé's postulates.

2. Written Report: In addition to the presentation, each group must submit a detailed written report, following the following structure:

   • Introduction: Students must contextualize the project, explaining the importance of Kekulé's postulates in organic chemistry and in our daily lives.
   • Development: Students must detail the theory of Kekulé's postulates, the description of the chosen compounds, and the methodology to build the molecular models. They should include photos of the models and discuss the results, explaining how the models demonstrate Kekulé's postulates, as well as the practical applications of each compound.
   • Conclusion: Students must summarize the main points, explicitly stating the learnings obtained and the conclusions drawn from the project.
   • Bibliography: Students must indicate the sources they relied on to work on the project.

This report will be a written record of the group's effort, effective collaboration, understanding of the theory, and practical execution of the project. It will be an opportunity to connect the theory learned with the practice carried out and to demonstrate the development of their technical and socioemotional skills.