Contextualization

Chemistry is a comprehensive and fascinating area, and one of the many aspects that make it so is the relationship between chemical substances and the energy involved in their transformations. This relationship is the basis for understanding the concept of enthalpy.

Enthalpy is a physical quantity that indicates the total energy of a thermodynamic system available to do work. In a chemical reaction, the system's enthalpy can increase or decrease, depending on whether the reaction is endothermic (absorbs heat) or exothermic (releases heat). Knowing how to calculate and interpret the enthalpy change is essential to understand and predict the behavior of many chemical reactions.

The enthalpy values of reactions are collected and tabulated for different standard conditions. This is very useful information for scientists, engineers, and technologists in various fields. Some enthalpies express the amount of energy needed to break bonds, while others express the energy released when new bonds are formed. Understanding these aspects is crucial for various fields, from drug synthesis to the development of new fuels.

Relevance of the Topic

We live in a world where energy issues are becoming increasingly relevant. Energy is needed for almost everything we do, from turning on a light bulb to moving a car. A deep understanding of the concept of enthalpy and how it plays a role in chemical processes can provide vital information not only to improve existing processes but also to discover new energy sources.

Chemistry plays a crucial role in many of the most pressing issues of our time, including environmental issues, sustainable development, and health. Therefore, the teaching of chemistry should focus not only on theoretical learning but also on the practical application of these concepts. In this project, we will seek to understand and apply the concept of enthalpy not only in a theoretical context but in a real and applied context.

Practical Activity

Color Change - Endothermic and Exothermic Reactions

Project Objective

The objective of this activity is to observe the difference between endothermic and exothermic reactions through color changes in a series of simple chemical reactions. Additionally, the activity aims to apply the concept of enthalpy in a practical and interesting way, encouraging teamwork.

Detailed Project Description

Students will be divided into groups of 3 to 5 members. Each group will perform two simple chemical reactions using acid-base indicators to visualize the color change as a result of the heat involved in the process.

The first activity will consist of an endothermic reaction, in which students will add an ice cube to a mixture of citric acid and sodium bicarbonate. In this reaction, the solution will change color, demonstrating that the reaction absorbs heat.

The second activity will be an exothermic reaction. In this one, students will mix sodium hydroxide with a little water and then add an acid-base indicator. The solution will change color, showing that the reaction releases heat.

Required Materials

To carry out the activities, the following materials are needed:

• Citric acid
• Sodium bicarbonate
• Sodium hydroxide
• Acid-base indicator (e.g., litmus paper)
• Two heat-resistant containers
• Spoon or spatula
• Safety goggles and gloves

Step-by-Step Guide for the Activity

1. For the first activity, add a tablespoon of citric acid and a tablespoon of sodium bicarbonate to a heat-resistant container.
2. Add an ice cube to the mixture and observe the color change.
3. Take notes of the observations and discuss in the group what the reaction means in terms of enthalpy.
4. For the second activity, place a tablespoon of sodium hydroxide in a heat-resistant container.
5. Add a little water. Make sure to do this in a well-ventilated area and use safety goggles and gloves.
6. Add the acid-base indicator to the mixture and observe the color change.
7. Discuss in the group what this reaction indicates about enthalpy.

Project Deliverables and Document Writing

After completing the practical activities, the groups should prepare a report addressing the following topics:

Introduction: In this section, the team should explain the concept of enthalpy, the importance of its study, and how it is applicable in the context of chemical reactions. It is important for students to contextualize the topic based on the research conducted.

Development: Here, the teams should explain in detail the reactions that were performed. The procedures, observations, and results should be clearly stated. Additionally, the group should discuss the theory behind endothermic and exothermic reactions and how this theory applies to the reactions they carried out.

Conclusions: This is the moment for students to reflect on the practical activity, summarizing the main points and explaining the learnings obtained, such as: differentiation between endothermic and exothermic reactions, observation of how enthalpy variation occurs, and the importance of these observations in the field of chemistry.

Bibliography: In this section, students should list all the sources they used to prepare the project. These can be books, websites, videos, among others.

Each team has one week to execute the project and submit the report.