Contextualization

Internal energy is a fundamental characteristic for us to understand the transformations that occur in the substances around us. In Chemistry, it is intrinsically linked to the notions of heat and work, using the concept of the first law of thermodynamics. Knowledge about internal energy is essential for other topics, such as enthalpy, entropy, Gibbs free energy, among others.

The internal energy of a system is the sum of all the energies of its constituents. This includes kinetic energy, related to the movement of particles, and potential energy, related to the interactions between particles. Understanding how internal energy behaves during chemical or physical transformations can help us predict the results of such processes and better understand the phenomena we observe daily.

The analysis of internal energy also allows us to perceive how this energy is transferred during a process, either in the form of heat or work. This transmission of energy is what enables machines to function, food to be cooked, among other things. It is a fundamental concept for us to understand how energy is used and transformed in our daily lives.

In the modern world, understanding internal energy is crucial in various sectors. In the industry, for example, efficient control of the internal energy of chemical processes can mean more efficient and less polluting production. In the food sector, control of internal energy is important for cooking and food preservation. Even in our bodies, the burning of calories and the maintenance of our body temperature are related to internal energy.

The resources we suggest for further study and as a basis for debates are:

• Book "Chemistry: The Central Science" by Theodore L. Brown, H. Eugene LeMay Jr., Bruce E. Bursten, Catherine J. Murphy, Patrick M. Woodward, and Matthew W. Stoltzfus. This book is a reference in the field of Chemistry and contains a chapter dedicated to chemical thermodynamics.

• Video "Internal Energy and the First Law of Thermodynamics | Chemistry | Khan Academy" available on YouTube. This video explains in a clear and objective way the concept of internal energy and the first law of thermodynamics.

• Website "Brasil Escola", which has a section dedicated to chemical thermodynamics with texts on internal energy.

Practical Activity

Activity Title:

"Designing a Solar Heater with Recyclables: A Multidisciplinary Study on Internal Energy".

Project Objective:

To study and apply the concepts of internal energy and the laws of thermodynamics in a practical way, building a homemade solar heater using recyclable materials. This project also aims to integrate chemistry with other disciplines such as physics and sustainability.

Detailed Project Description:

Students will work in groups of 3 to 5 people, for a minimum period of one month, to carry out the project.

The group's task is to design and create an efficient solar heater using recyclable materials. They must document the entire process, including the theory involved, the materials used, the construction steps, the tests performed, and the results obtained.

During the project execution, students must perform internal energy calculations, applying the first law of thermodynamics, to predict and verify the efficiency of the solar heater.

Through this project, students will be challenged to apply theoretical concepts in practice and develop skills such as teamwork, time management, problem-solving, and critical thinking.

Required Materials:

• PET bottles
• PVC pipes
• Black paint
• Thermal insulator
• Hose
• PVC adhesive
• Tape measure
• Scissors
• PVC cutting saw
• Ruler

Detailed Step-by-Step for Activity Execution:

1. Research and Planning: Students should research how to build a homemade solar heater model. Then, they should design the heater based on what they have learned and the materials they have.

2. Construction of the Solar Heater: Students must follow the design and build the solar heater. They should document all steps with photos or videos, and note any problems encountered and how they solved them.

3. Testing and Data Collection: After construction, they should test the solar heater in different weather conditions (sunny, cloudy, windy) and record the results.

4. Data Analysis: Students must analyze the collected data, including internal energy calculations and the efficiency of the solar heater.

Project Deliverables and its Connection with the Suggested Activities:

At the end of the project, students must produce a detailed report on the work done.

1. Introduction: Should explain the concept of internal energy, thermodynamics, and the importance of research and the use of sustainable energies. It should also present the project's objective and its relevance.

2. Development: Should present the theory behind the construction of the solar heater, detail the materials used, the project steps, the calculations performed, as well as the results obtained.

3. Conclusion: Should discuss the lessons learned, the efficiency of the solar heater, the application of theoretical concepts in practice, and the group's final conclusions.

4. Bibliography: Should contain all bibliographic sources consulted by the group members for the project.

Students must understand that the purpose of this project is not only to complete all tasks but to apply the concepts of internal energy and thermodynamics in practice, in a meaningful and sustainable way, and be able to discuss the impact and implications of their project.