Contextualization

Chemical kinetics is the area of chemistry that studies the rate of reactions, the factors that influence it, and the mechanisms by which they occur. Each chemical reaction has a rate that depends on several factors, such as the concentration of the reactants, the temperature of the system, the contact surface between the reactants (in solids), the occurrence of a catalysis, and the activation energy.

The activation energy is the minimum amount of energy required for a chemical reaction to occur. In other words, activation energy is the energy "barrier" that reactants must overcome to transform into products. This is because, for molecules to react with each other, a certain amount of energy must be supplied to break the initial bonds and start the new bonds. The activation energy can be observed in a graph of potential energy versus time during a chemical reaction.

Understanding activation energy is crucial to understanding how chemical reactions occur and why some reactions are faster than others. Activation energy is a fundamental concept in chemical kinetics and is useful for predicting how a change in reaction conditions (such as temperature) will affect the reaction rate.

Chemical kinetics, and in particular the concept of activation energy, have important applications in our daily lives. For example, the fact that food takes much longer to cook at high altitudes is due to the decrease in atmospheric pressure, which increases the activation energy for the cooking reaction. Also, activation energy is a key factor in the operation of catalysts, which are used to speed up chemical reactions in many industrial applications, such as the production of fertilizers and petroleum refining.

To delve deeper into the subject, I suggest the following sources of information:

1. Khan Academy: Chemical Kinetics Course
2. General Chemistry Book - Vol. 1 (John B. Russell)
3. University of São Paulo (USP) website

Practical Activity: Activation Energy and the Phosphorus Reaction

Project Objective

The objective of this project is to understand and demonstrate the concept of activation energy, realizing how the variation in temperature can affect the rate of a chemical reaction.

Detailed Project Description

Student groups will conduct an experiment to compare the combustion rate of a match in two different temperature conditions. They will analyze the results to assess the influence of temperature on activation energy and reaction rate. Furthermore, they should calculate the activation energy required for phosphorus combustion using the Arrhenius Equation.

Required Materials

1. Matches
2. Refrigerator (or cold location)
3. Stopwatch
4. Recording camera (can be a cell phone)
5. Protective gloves
6. Software or application for video analysis (recommended: Tracker Video Analysis)
7. Calculator
8. Computer with internet access (for research and writing the report)

Step-by-step detailed instructions for carrying out the activity

1. Separate three matches.
2. Place one of them inside the refrigerator and leave it for at least an hour. The other two will stay at room temperature.
3. After waiting, one member of the group should light one of the matches that were at room temperature, while another times how long it takes to burn completely. The action must be recorded on video.
4. Repeat the same process with the other match at room temperature.
5. Now, remove the match that was in the refrigerator. Without wasting time, light it and time how long it takes to burn completely, also filming the process.
6. Analyze the videos using the analysis software to confirm the burning time.
7. With the burn times recorded, do research to find the theoretical activation energy values for phosphorus combustion at different temperatures.
8. Use the Arrhenius Equation to calculate the activation energy of the phosphorus reaction at different temperatures.

Project Deliverables

After conducting the experiment, the students should write a report with at least four main topics: Introduction, Development, Conclusions, and Bibliography used.

1. Introduction: Contextualization of the topic, its relevance and real-world application, as well as the objective of this project.
2. Development: Explanation of the activation energy theory and chemical kinetics, details of the experiment performed, presentation of the methodology used, and finally, presentation and discussion of the results obtained.
3. Conclusions: Recapitulation of the main points, reflection on the learnings obtained, and conclusions drawn about the project.
4. Bibliography: Indication of the sources that were consulted during the project, such as books, web pages, videos, etc.

The report will help demonstrate the knowledge acquired, as well as stimulate important skills such as analytical ability, technical writing, teamwork, and time management.