Contextualization
The study of the work done by a gas is an important topic in Physics and of great relevance in various fields of science, such as engineering and chemistry. Understanding this subject can help comprehend how thermal engines work, for example, as well as contribute to the development of more efficient and sustainable technologies.
Firstly, it is necessary to understand what a gas is in physical terms. A gas is formed by a large number of particles (atoms, molecules, or ions) in constant random motion colliding with each other and with the walls of the container that contains it. These collisions generate force and, consequently, pressure.
The work done by a gas is defined as the energy transferred from a gas to its environment (or vice versa) through a pressure applied over a change in volume. There are several gas transformations where this work can be performed, such as in isothermal transformations (constant temperature), isobaric transformations (constant pressure), isovolumetric transformations (constant volume), or adiabatic transformations (without heat transfer).
The connection between the work of a gas and its applications in the real world is vast. Automobile engines, gas turbines, hot air balloons, and even our breathing are examples of systems that involve the work of a gas. By understanding how a gas performs work, we can improve the efficiency of these systems and think of solutions for energy and sustainability issues.
Due to its complexity and scope, the subject requires a deep and careful study, capable of relating theoretical concepts to practical applications. For this, we provide some reliable sources:
- Brazil School - Physics - Work of a Gas
- World Education - Work of a Gas
- Book: Halliday, D., Resnick, R., & Walker, J. (2008). Fundamentals of Physics: Gravitation, Waves, and Thermodynamics. Vol. 2, LTC publisher.
Through reading and debating the content of these sources, it will be possible not only to understand the theory behind the work of a gas but also to develop a critical view of its implications and applications.
Practical Activity: Construction of a Stirling Engine
Project Objective:
In this activity, we want you to apply in practice the theoretical concepts of the work of a gas studied so far. You must build a Stirling Engine, which is a closed-cycle thermal engine that operates through the expansion and contraction of a gas.
This project should be carried out in groups of 3 to 5 students, and its execution should require more than twelve hours per participating student.
Detailed Project Description:
The construction of a Stirling Engine will provide a practical experience of the main concepts involved in the work of a gas: gas transformations and the performance of work by a gas through expansion and contraction in response to temperature changes.
In addition, the project will also involve notions of mechanics (such as the movement of a piston in a cylinder) and chemistry (by selecting the gas to be used in the engine and understanding its thermal behaviors).
To guide the construction of your Stirling Engine, you must follow the Step by Step described below. However, we encourage the search for alternative and creative solutions to overcome obstacles and improve the engine's performance.
Necessary Materials:
- Soda cans
- Transparent and resistant glass or plastic tubes
- Latex balloons
- Wire
- Insulating tapes
- Candle or another heat source
- Basic tools such as pliers, scissors, and hot glue.
Step by Step:
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Initial Study: All group members should search for bibliographic references and tutorials on building a Stirling Engine. It is important to understand how the engine works and identify the main challenges of construction. This is the first step in carrying out the project.
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Planning: Use the collected information to draw a diagram of your engine, listing the materials that will be used in each part of the engine. Remember that the Stirling Engine is composed of two cylinders (one hot and one cold) and a piston that moves the gas between them.
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Construction: With the project in hand, gather with your colleagues to build the engine. Remember to follow safety recommendations when using tools and dealing with fire in the testing phase.
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Tests and Adjustments: After completing the assembly, carry out tests to verify the engine's operation. It may be necessary to make adjustments to parts that are not working as expected or improve parts that can perform better.
Project Deliverables:
- Report: Each group must present a detailed report of the project. The report should contain:
- Introduction: A detailed description of the work of a gas and its application in the Stirling Engine. The introduction should contextualize the theme, its relevance and application in the real world, as well as the objective of this project.
- Development: Here, you should describe all stages of project execution, from information gathering to construction and testing of the engine. Be detailed in explaining the problems encountered and how they were solved. Include images and graphs, if necessary.
- Conclusions: Summarize the main points, indicating what were the learnings and experiences obtained, as well as the conclusions drawn from the project.
- Bibliography: Indicate the sources on which you based your work on the project such as books, web pages, videos, etc.
- Presentation: Each group will make an oral presentation of the project to the class, demonstrating the engine's operation and discussing the challenges encountered during the project execution.
In addition to providing a great practical experience, we hope that this project will help you develop important skills such as teamwork, problem-solving, communication, proactivity, and time management.
