Contextualization

Theoretical Introduction

Lavoisier's law, also known as the Law of Conservation of Mass, is one of the fundamental laws of Chemistry. It was stated by the French chemist Antoine Laurent Lavoisier (1743-1794) and postulates that, in a chemical reaction that occurs in a closed system, the total mass of the reactants is equal to the total mass of the products. This principle reveals the conservation of matter, leading to the idea that matter is neither created nor destroyed, it simply transforms.

Chemistry is a branch of science that studies matter, its properties, composition, structure, and the transformations it undergoes. The laws of Chemistry are based on experimental observations and describe the behavior of matter under certain conditions. Lavoisier's Law is an example of these laws, being essential to understand how atoms rearrange during chemical reactions.

It is worth noting that Lavoisier's law is valid for most chemical reactions, but there are situations, especially in particle physics, where the law of conservation of mass-energy, derived from Einstein's theory of relativity, is more appropriate. However, for many everyday and industrial situations, and for didactic purposes at the high school level, Lavoisier's law is sufficient to explain what happens during a chemical reaction.

Relevance of the Theme

Understanding Lavoisier's Law is fundamental for the comprehension of chemical science, as it is the basis for a series of different concepts and practices in this discipline. In our daily lives, we are constantly surrounded by processes that follow Lavoisier's law. Whether cooking, playing with modeling clay, mixing ingredients to make slime, all these processes respect the law of conservation of mass.

Furthermore, professionals working with chemical processes need to have a good understanding of Lavoisier's Law. The development and production of medications, the manufacturing of plastics and composite materials, the processes involved in food and beverage production, the search for alternative sources of energy, and countless other industrial activities depend on a proper understanding of this law. Being able to balance a chemical equation is an essential skill in many scientific careers, from chemical engineering to biotechnology.

Practical Activity

Activity Title: "In Balance: Proving the Law of Lavoisier"

Project Objective

The objective of this project is to provide students with the opportunity to experimentally verify Lavoisier's Law, also known as the Law of Conservation of Mass. In addition to learning and applying chemistry concepts, students will also learn about the scientific process, how to conduct an experiment, analyze and interpret data, and how to write a scientific report.

Detailed Project Description

Students should form groups of 3 to 5 people and organize themselves to carry out a simple experiment that demonstrates Lavoisier's Law. After the experiment, students should write a detailed report documenting the entire process, data analysis, and conclusions. The whole process should last more than 12 hours per student.

Required Materials

• Precision scales (2x)
• Glass containers with lids (2x)
• Baking soda
• Vinegar
• Protective gloves
• Protective goggles
• Lab coats
• Stopwatch

Detailed Step-by-Step

1. Planning: Before starting the experiment, groups should research more about Lavoisier's Law and what they expect to observe. They should create a detailed plan on how they will conduct the experiment, including safety measures and how they will collect and analyze the data.

2. Weighing the Materials: Using one of the precision scales, students should weigh the amount of baking soda and vinegar that will be used in the experiment.

3. Experiment Execution: Since the reaction between baking soda and vinegar occurs rapidly, students should work in a coordinated manner to add the baking soda to the vinegar and immediately close the container. It is important that the container is closed to ensure that the system is closed (thus fulfilling the closed system condition of Lavoisier's Law).

4. Data Collection: After the reaction has occurred and the system has reached an equilibrium state, students should weigh the container with the reaction products using the other precision scale.

5. Data Analysis: Students should then compare the mass of the reactants with the mass of the products and discuss if the results are in accordance with Lavoisier's Law.

6. Report Writing: Finally, students should write a report detailing the entire process, data analysis, and conclusions.

Project Deliverables

Students must submit a written report, which should include the following topics:

1. Introduction: Contextualization of the theme, its relevance and real-world application as well as the objective of this project.

2. Development: It should detail the theory behind Lavoisier's Law, explain the experiment in detail, indicate the methodology used, and present and discuss the results obtained.

3. Conclusion: It should summarize the main points of the work, explain the learnings obtained, and draw conclusions about the project.

4. Bibliography: It should indicate the sources used to work on the project.

The report should be written in a way that complements the project experience. The discoveries from the experiment and the group's reflections on the experiment and Lavoisier's Law should be clearly expressed. The report will be used to evaluate not only the technical knowledge of the students but also their collaboration and teamwork skills.