Contextualization

Chemistry, gentlemen, is the science that studies matter, its compounds, and the transformations it can undergo. Within this broad field of study, one of its most intriguing areas is chemical kinetics - which is dedicated to understanding the speed of these transformations and the factors that influence it.

Chemical kinetics investigates the rate of change in the concentrations of reactants and products over time. Through it, it is possible to know how quickly reactants are converted into products, thus allowing to predict the duration of a specific reaction. In this universe, a fundamental concept is that of 'reaction order'.

In a simplified way, the reaction order is how we classify a chemical reaction according to the behavior of the reaction rate in relation to the concentration of the reactants. The reaction order can be zero, one, or two, each with its own peculiarity, significantly influencing the progress of the reaction.

In our daily lives, chemical kinetics and reaction order are present in various situations. For example, the manufacturing process of various products, such as medications, food, paints, cosmetics, among others, requires the correct understanding of the concepts of chemical kinetics to ensure efficient and safe production. Furthermore, in the field of environmental protection, chemical kinetics is essential for understanding phenomena such as the degradation of pollutants and the formation of ozone in the troposphere.

In this sense, it is extremely relevant that we understand in practice how these concepts operate. For this, it is essential that we make use of experiments and practices that allow us to visualize and understand these phenomena in a more tangible way.

To deepen their knowledge, students can resort to reliable sources:

1. Book 'Chemistry: The Central Science' by Brown, Lemay, and Bursten
2. 'Brasil Escola' website with topics on Chemical Kinetics (Link here)
3. Videos on the 'Química em Ação' channel by Professor Paulo Valim on YouTube, especially the playlist on Chemical Kinetics (Link here)
4. Videos on the 'Quiprocura' channel with various chemical kinetics experiments (Link here)

Practical Activity

Activity Title: 'Unraveling the Order: A Practical Study in Chemical Kinetics'

Project Objective:

To understand the concept of reaction order through the execution of a practical experiment, data analysis, and report writing.

Detailed Project Description:

Each group, composed of 3 to 5 students, will conduct an experiment involving the effervescent tablet dissolution reaction in water. The goal is to determine the reaction order of this process, applying the concepts of chemical kinetics and using data analysis methods.

The project will last at least 12 hours per student, which can be divided over several study and teamwork sessions.

Required Materials:

• Effervescent tablets (of the same type)
• Water (at the same temperature for all attempts)
• Transparent cups or containers (of the same volume)
• Stopwatch
• Thermometer
• Precision scale
• Camera (a smartphone can be used for this purpose)
• Calculator
• Software to analyze videos (there are free and paid apps available)

Detailed Step-by-Step:

1. Planning: Students must plan how they will conduct the experiment, including how they will collect and analyze the data.

2. Experiment Execution:

   • Each group performs several attempts of the experiment, following these steps:
     1. Weigh the effervescent tablet and record the value.
     2. Add the tablet to the water inside the container.
     3. Start the stopwatch at the same time the tablet is inserted into the water.
     4. Record the process until the tablet is completely dissolved.
     5. Record the final time.
   • Repeat the process varying the mass of the effervescent tablet (for example, using half a tablet, a quarter of a tablet), keeping the water volume constant.

3. Data Analysis: Use the software to analyze the videos and record the time it takes for the tablet to dissolve in each attempt. Compare the times and analyze how the change in the tablet mass influences the dissolution time.

4. Interpretation: Based on the collected data, students must determine the reaction order concerning the effervescent tablet. They must justify their conclusion based on the theory learned in class about chemical kinetics and reaction order.

5. Report: Students must write a report that includes the introduction (contextualization and objective), development (explanation of the theory, activity description, methodology, presentation and discussion of results), conclusion (learnings and conclusions drawn from the project), and the bibliography used.

The report should include, but is not limited to, the following main topics:

Introduction: Contextualization of the theme, relevance and real-world application, project objective.

Development: Explanation of the theory of chemical kinetics and reaction order concepts, detailed description of the experiment execution, presentation of collected data and analysis, interpretation of results and comparison with the studied theory.

Conclusions: Recap of the main points, explicitly stating the learnings obtained and conclusions drawn from the project.

Bibliography: Sources used to work on the project, such as books, web pages, videos, etc.

The project deliveries include the executed experiment, the collected and analyzed data, the interpretation of results, and the report writing.

The project helps develop technical skills such as formulating questions, hypotheses, predictions, and estimates; using measuring instruments; representing and interpreting models, data, and/or experimental results; constructing, evaluating, and justifying conclusions; understanding and calculating the reaction order. Additionally, socio-emotional skills such as time management, communication, problem-solving, creative thinking, and proactivity are also fostered throughout the project.