Contextualization

By understanding temperature, we have the possibility to control and develop numerous processes in our daily lives, from the simple act of refrigerating our food to the elaboration of complex industrial chemical reactions. But have you ever stopped to think about how we measure temperature? In our reality, we use thermometers, and these instruments are based on the properties of certain substances that change with temperature variation.

Introduction

The study of thermometer scales is fundamental to understanding heat exchange and thermodynamic processes. In physics, there are three such scales: Celsius, Fahrenheit, and Kelvin. Each one has its origin, its use, and its relevance, whether in everyday life or in the scientific community. The Celsius scale is widely used in almost the entire world for daily activities and in the metric system. The Fahrenheit scale, on the other hand, is used in a few countries, mainly English-speaking ones, for everyday purposes.

The Kelvin scale, in turn, is used in the scientific community, as it is the absolute scale, i.e., it is impossible for there to be a temperature lower than 0 Kelvin (absolute zero). It is important in the development of studies related to the Third Law of Thermodynamics. Understanding these scales and their relationships is fundamental to performing more complex thermodynamic calculations and analyses.

Relevance

Changing the temperature scale is a simple but fundamental action in everyday life and in scientific and industrial practice. For example, when cooking using a foreign recipe, you may have to convert temperatures from Fahrenheit to Celsius. In a scientific context, experiments that deal with extremely low temperatures, such as in the study of superconductivity, generally use the Kelvin scale.

Familiarity with these scales and the ability to convert between them are important skills for anyone, not just scientists. In addition, understanding thermometer scales and their conversions allows us to better understand the world around us.

Reference materials

To deepen your knowledge on the subject, I recommend the following sources:

• Book "Fundamentals of Physics" by David Halliday & Robert Resnick, volume 2, chapter 18 - Presents the theory of thermometer scales in a complete way.
• The website Brasil Escola has a section dedicated to teaching Physics, including topics on thermodynamics and thermometer scales. Access it here: Brasil Escola - Thermometer Scales
• Videos on Youtube can be a great way to learn visually. I recommend the channel "Ciência Todos os Dias" (Science Every Day), which has a video explaining thermometer scales and their conversions. Watch it here: Ciência Todos os Dias - Thermometer Scales

Hands-on Activity: "Exploring Thermometer Scales"

Project Objective

The objective of this project is to build a homemade thermometer and use this tool to understand the different thermometer scales. In groups of 3 to 5, students will measure temperatures in different environments and then convert these measurements between the three main scales (Celsius, Fahrenheit, and Kelvin) and to a non-traditional scale chosen by the group.

Project Description

In this activity, the groups will create a homemade thermometer using common materials, such as plastic bottles, alcohol, straws, among others. With the thermometer built, the students will create an experiment to measure the temperature of different environments, such as a refrigerated room and a room in the sun, for example.

After collecting the data, the students will delve into the study of thermometer scales, converting the measured temperatures to the Fahrenheit, Kelvin, and another scale chosen by the group. Based on these conversions, the students will perform a comparative analysis between the scales and the importance of each one in different contexts.

Required Materials

• 1 plastic bottle (transparent and with a lid);
• Plastic straw;
• Adhesive tape;
• Alcohol (ethyl or isopropyl);
• Food coloring;
• Clay or modeling dough;
• Conventional thermometer (to calibrate the homemade thermometer);
• Notebook for notes and calculations.

Step-by-Step Activity

1. Building the Homemade Thermometer: First, the alcohol should be colored with the dye and inserted into the bottle until it fills about 1/4 of it. Then, the straw should be positioned inside the bottle, but without touching the bottom, and fixed to the mouth of the bottle with adhesive tape, so that it is sealed (it cannot allow the passage of air). Finally, the clay or modeling dough will be used to seal the mouth of the bottle even more and better fix the straw, ensuring that there are no leaks. The tip of the straw that is inside the bottle should be submerged in the alcohol.

2. Calibrating the Homemade Thermometer: With the help of a conventional thermometer, the students should mark on the straw the temperatures corresponding to 0ºC, 10ºC, 20ºC, 30ºC, and so on.

3. Carrying out the Experiment: The students will take the thermometer to different environments and write down the temperatures observed in each place.

4. Scale Conversion: With the temperature measurements collected, the students should convert these measurements to the Fahrenheit and Kelvin scales using the conversion formulas. In addition, the students should choose a non-traditional scale, research the conversion formula for that scale, and convert the collected measurements.

5. Analysis of Results: Based on the conversions performed, the students will make a comparative analysis between the scales and discuss the importance of each one in different contexts.

Project Delivery

After completing the practical part, the students should organize a report with the following topics:

1. Introduction: It should contain a contextualization on the subject, the relevance of thermometer scales, and the objective of the project.
2. Development: Here, the students should present the theory of thermometer scales, a detailed description of the activity performed, the methodology used, and the results obtained, as well as the discussion of these results.
   • In the description of the activity, the students should report all the details of the construction of the thermometer, the data collection, and the conversions performed.
   • In the presentation and discussion of the results, the students should present the temperatures measured in each environment and in the different scales. They should also discuss the reason for choosing the non-traditional scale and its peculiarities.
3. Conclusion: The students should conclude the work by returning to their main points, explaining the lessons learned, and the conclusions drawn about the project.
4. Bibliography: The sources used to work on the project, such as books, web pages, videos, etc., should be indicated.

The project should be delivered within one week and each participating student should dedicate two to four hours to its execution.