Introduction

Thermodynamics is one of the most fascinating branches of chemistry, exploring the reactions and mixtures of matter and their energy and heat changes. During general chemistry classes, you were introduced to the concepts of eutectic and azeotropic mixtures. Considering this, we are about to embark on a project that will expand knowledge about these mixtures, taking you beyond theory and diving into a practical experience.

Eutectic mixtures are those that present, in their phase diagram, a constant melting point. This characteristic point is called the eutectic point and represents the temperature at which the mixture transitions from solid to liquid or vice versa, without a change in temperature. Azeotropic mixtures, on the other hand, are those in which the components have such similar volatilities that, when heated, their vapors maintain the same composition as the original mixture. In other words, they are mixtures that behave as if they were pure substances during evaporation or condensation.

These concepts are fundamental for a better understanding of the properties of matter and the interactions between molecules. Known as constant mixtures, eutectic and azeotropic mixtures pose a challenge to the principle that associates temperature variations with phase changes. Therefore, they are intriguing topics full of potential for the development of an educational and engaging project.

Contextualization

Understanding eutectic and azeotropic mixtures is of great relevance both in industry and in the research and development of new materials. For example, in the food industry, the use of eutectic mixtures in various types of chocolates is very common, such as milk chocolate, where sugar and cocoa butter form a eutectic mixture that melts in the mouth, providing that unmatched flavor.

Similarly, azeotropic mixtures are of paramount importance in sectors such as fuels and solvents. For example, gasoline, a fuel that we are all very familiar with, is a complex mixture of hydrocarbons that, in some compositions, can behave similarly to an azeotropic mixture.

Therefore, studying these types of mixtures goes beyond simply fulfilling an academic requirement. It is knowledge that can be applied in various areas of science, technology, and industry, whether in pharmaceuticals, food, chemicals, materials, among others.

Practical Activity

Title: Exploring Mixtures: Building and Analyzing Eutectic and Azeotropic Cooling Curves

Project Objective

The objective of this project is to lead students to explore eutectic and azeotropic mixtures, both theoretically and practically, by building their cooling curves and, finally, producing a complete and detailed report of their findings.

Project Description

The student groups should initially carry out a theoretical study on eutectic and azeotropic mixtures in order to build a solid knowledge base. They should then conduct experiments to build cooling curves for both a eutectic and an azeotropic mixture. Finally, they should prepare a report detailing their discoveries and comparisons between these two mixtures.

Required Materials

• Mixtures identified by the teacher for the experiments (one eutectic mixture and one azeotropic mixture);
• Beaker or heat-resistant glass container;
• Thermometer;
• Stopwatch or clock with second counting;
• Stove or hot plate (if adult supervision is required, please provide);
• Computer with Excel or another graphing program.

Step by Step

1. Each group should start the project with a theoretical research on eutectic and azeotropic mixtures, using the suggested material and other reliable sources. In this research, key points about what characterizes each of these mixtures and how they differ from conventional mixtures should be noted.

2. With the acquired theoretical knowledge, the group should heat the eutectic mixture in the beaker until it reaches the liquid state. Then, they should start the cooling process, noting the temperature at regular intervals (recommended every 30 seconds).

3. The same process should be carried out with the azeotropic mixture.

4. With the collected data, the groups should construct temperature versus time graphs for each mixture, the so-called cooling curves.

5. Analyze the constructed graphs and compare the results with the theory learned. Observe points such as the temperature behavior over time, the presence or absence of a constant temperature during cooling, and what this indicates about the mixture.

Project Deliverables

At the end of the project, each group should deliver a report containing:

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

2. Development: Here, students should explain in detail the theory learned about eutectic and azeotropic mixtures, as well as present the methodology used, explaining each step of the experiment conducted. The results obtained should also be presented, showing the cooling curves and analyzing them in light of the theory studied.

3. Conclusion: Revisiting the main points, students should explain the learnings obtained, their interpretations of the results, the difficulties encountered, and the conclusions drawn from the project.

4. Bibliography: Indication of the sources on which they relied for the study and execution of the project.

At the end of this project, students will not only have learned about eutectic and azeotropic mixtures, but will also have developed important skills such as time management, effective communication, problem-solving, critical thinking, and worked on proactivity, establishing a more solid relationship with the scientific method and its applicabilities.