Contextualization

Thermodynamics is a fundamental part of physics that studies the relationship between heat, work, and energy. One of its most important laws is the First Law of Thermodynamics, also known as the Law of Conservation of Energy. According to this law, energy cannot be created or destroyed, only transformed. This is a crucial idea that permeates all of physics and is essential for understanding many natural phenomena and technologies we use in our daily lives.

The First Law of Thermodynamics is mathematically expressed by ΔU=Q+W, where ΔU is the change in the internal energy of a system, Q is the amount of heat exchanged by the system, and W is the work done by the system. This equation tells us that the increase in the internal energy of a system is equal to the heat added to the system minus the work done by the system. This is an important tool for analyzing processes involving heat and work exchanges, such as car engines, refrigeration systems, among others.

Understanding the First Law of Thermodynamics is essential to comprehend how energy is transformed and how these transformations affect the world around us. Without this law, we would not be able to explain how a gasoline engine works, how our bodies burn calories, or how a plant converts sunlight into chemical energy through photosynthesis. Understanding this law allows us to predict and manipulate these energy transformations to create new technologies and solve problems we face in the modern world.

Physics is not only a theoretical discipline but also a practical tool to understand and transform the world. The first law of thermodynamics is a perfect example of this. If we look around us, we will see that it is in action in virtually every aspect of our daily lives. From the simple act of boiling water to make tea to the complex operation of a nuclear power plant, the first law of thermodynamics governs the flow of heat and work in our world.

When we delve into this concept, we not only gain a deeper understanding of the physical sciences but also develop valuable skills such as critical thinking, problem-solving, and understanding of the scientific method. Thus, learning the first law of thermodynamics is not just a matter of passing a test or obtaining a degree, but a crucial step in our development as educated individuals and informed citizens.

For those who wish to delve deeper into the study, the following reliable resources are suggested:

1. First Law of Thermodynamics - Brasil Escola
2. Thermodynamics - Universidade Online de Viçosa
3. First Law of Thermodynamics - Khan Academy (videos in Portuguese with transcription)

Practical Activity: Assembling and Analyzing a Stirling Engine

Project Objective

The objective of this project is to apply the concept of the First Law of Thermodynamics in a practical and experiential context through the assembly and analysis of a Stirling engine. The Stirling engine is an example of a heat engine that operates through the expansion and contraction of a gas, ideal for demonstrating the First Law of Thermodynamics.

Project Description

Students, in groups of 3 to 5, will assemble a Stirling engine using common materials. After assembly, they will analyze the engine's operation, recording their observations and calculating the internal energy, work done, and heat exchanged, using the First Law of Thermodynamics.

Required Materials

1. Aluminum cans (2).
2. Copper or aluminum wire.
3. Latex balloon or bladder.
4. Wire.
5. Ignition candles (4).
6. Ignition candle adapter.
7. Voltage regulator.
8. Piston (can be constructed with wood and metal rods).
9. Glass test tube.
10. Plastic straw.
11. Hot glue.
12. Thermometers (2).
13. Multimeter.

Step-by-Step for Activity Execution

1. Students should start by drawing and planning the assembly of the Stirling engine. They should research and discuss different Stirling engine designs and choose the one that best fits the available materials.

2. Next, they should assemble the engine. The Stirling engine is basically composed of two aluminum chambers connected by a glass test tube. One of the chambers contains a piston, which moves up and down due to the expansion and contraction of the gas inside the chamber, generated by the alternate heating and cooling of the chamber. The latex balloon or bladder serves as a diaphragm, allowing the piston to move without gas loss.

3. After assembling the engine, students should perform an initial test to verify that everything is working correctly. They should light the ignition candles and observe if the piston starts to move.

4. Once the engine is working correctly, students should start collecting data. They should measure the temperature of the hot and cold chambers, as well as the voltage and current produced by the engine. This data will be used to calculate the work done, internal energy, and heat exchanged.

5. After collecting the data, students should use it to calculate the work done (W), the change in internal energy (ΔU), and the heat exchanged (Q), using the First Law of Thermodynamics.

6. Finally, they should write a detailed report on the project, including the theory of the First Law of Thermodynamics, the description and objective of the project, the methodology used, the calculations performed, and the discussion of the results obtained. The report should also include the conclusions drawn from the project and the bibliography used.

Project Deliverables

Students must deliver the assembled Stirling engine and a detailed report that includes:

1. Introduction: Contextualization of the First Law of Thermodynamics, relevance of the topic, and objective of this project.
2. Development: Detailed discussion of the theory behind the First Law of Thermodynamics, detailed description of the practical activity (construction and analysis of the Stirling engine), methodology used, presentation and discussion of the calculations and results obtained.
3. Conclusion: Review of the main points of the work, discussion of the learnings obtained, and conclusions drawn about the project.
4. Bibliography: References of all sources consulted during the project.

This report should be written in a clear and understandable manner and should connect the practical activity carried out with the theory studied, in order to demonstrate the students' understanding of the First Law of Thermodynamics.