Contextualization

Chemical kinetics is the branch of chemistry that studies the speed of chemical reactions and also how they occur. That is, it studies the speed at which the reactants are consumed and the products are formed. In a world that is always in a hurry, chemical kinetics is fundamental to many segments of industry and science. The Rate Law is an important part of chemical kinetics, as it relates the consumption rates of reactants or the formation of products with the concentrations of chemical species present in the mixture. Knowledge of how the speed of a reaction changes with the concentration of its reactants is crucial for many practical applications, including controlling the speed of chemical processes. In industry, it is common to need to increase or decrease the speed of a reaction, and for this it is necessary to know the Rate Law of that reaction. In situations where the speed of the reaction is important, such as in explosive reactions or in the production of medicines, knowledge of the Rate Law is essential.

Introduction

To begin exploring this fascinating aspect of science, groups of students will be challenged with the "Reaction Race" project. In this project, students will have the opportunity to experience the Rate Law first-hand. They will not only study the theory, but will be able to put their hands in the dough and see the concepts in action. You will understand that chemistry is not only applied to textbooks, but also to everyday situations. Each group will be responsible for studying a chemical reaction, evaluating the speed of that reaction and connecting the theoretical concepts with the experimental results. They will work collaboratively, applying the concepts of chemical kinetics and Rate Law to perform and interpret chemical experiments. Below you will find a list of reliable and interesting resources that will help you deepen your knowledge on the subject and provide a solid foundation for the project:

1. Book "Chemical Kinetics and Catalysis", by José Moura Bordalo and Ernesto Raphael Hartung (Edgard Blucher Publisher)
2. Website of the Department of Chemistry of the University of Coimbra with an article on Chemical Kinetics
3. Classes on Chemical Kinetics on the channel Chemistry with Prof. Paulo Valim - Science in Action on YouTube

Practical Activity: "Reaction Race"

Project Objective

Students will work in groups of 3 to 5 members to conduct an experimental study on the speed of a chemical reaction. The main objective is for students to relate the theory of Chemical Kinetics and Rate Law to experimental results and identify how different variables influence the speed of a reaction.

Project Description

Students will choose a simple and safe chemical reaction (to be approved by the teacher) and design an experiment to measure its speed. They will need to make predictions based on theory and then conduct the experiment to test those predictions. With the data collected, students will determine the rate law of the reaction.

Some examples of reactions that can be studied include: the reaction of baking soda with vinegar, the reaction of hydrogen peroxide with potassium iodide, the reaction of hydrochloric acid with calcium carbonate, among others.

Materials Required

The specific materials to be used will depend on the reaction chosen, but in general, students will need:

1. Reagents for the reaction
2. Basic laboratory equipment (test tubes, pipettes, stopwatch, etc.)
3. Safety equipment (goggles, gloves, etc.)
4. Paper and pen for notes

Step by Step

1. Study of the theory: The first step will be to review the theory of Chemical Kinetics and Rate Law. Students will do an in-depth research and present the information in a report that will include an introduction to the subject.

2. Choice of reaction and prediction of the rate law: Students will choose a chemical reaction and make a prediction of the rate law based on theory.

3. Design of the experiment: Students will describe in detail how they will measure the speed of the chosen reaction.

4. Carrying out the experiment: Students will carry out the experiment following the protocol they have designed, collecting data and making notes of all relevant observations.

5. Data analysis and determination of the rate law: With the data collected, students will determine the rate law for the reaction and compare it with the prediction they made.

6. Report preparation: Finally, each group will prepare a report detailing the entire process, from the review of the theory, through the design and execution of the experiment, to the analysis of the data and the determination of the rate law. This report should follow the structure explained in the introduction to this project.

Project Deliverables

As project deliverables, groups must submit:

1. Written report: The report should be presented in the format of a scientific article, including Introduction (relevance and objective of the project), Development (theory, detailed description of the activity, methodology and presentation/discussion of the results), Conclusions and Bibliography.

2. Oral presentation: The groups will make an oral presentation to the rest of the class, explaining their experiment and sharing their analysis of the results.

This project is designed for students to put into practice the theoretical concepts of Chemical Kinetics and Rate Law. They will be able to describe and explain these theories, design and conduct an experiment, analyze scientific data and present their results in a clear and concise manner.