Contextualizing

Introducing Chemistry into the real world: the relevance of Bases.

Chemistry is a science that studies matter, its properties, composition, structure, transformations and energy. This science is not only present in textbooks: it is everywhere around us, and understanding it enables us to better comprehend the world in which we live, and even ourselves.

One of the crucial components of chemistry are bases, which are fundamental concepts to understand chemical events that occur in our day-to-day lives. They are substances which, when dissolved in water, release OH- ions (hydroxide). They have caustic properties, feel slippery to the touch, can change the colour of indicators and react with acids to form salt and water in a process called neutralisation.

Throughout this project, we will not only explore the chemistry of bases, we will also learn about their practical applications, as well as study safety in activities related to these compounds. Did you know that when you experience the bitter taste of coffee, you are experiencing a base? Or when we use soap to clean our hands, the base present in the soap neutralises the dirt’s acids? These are just some examples of how bases are present in our routine.

But beyond our day-to-day lives, bases also have important industrial applications. They are present in the production of soaps and detergents, in the production of medicine, in the production of paper, in the textile industry, among others. Additionally, various chemical processes in industries involve reactions with bases, such as the treatment of water and sewage.

In order to further solidify your knowledge about bases, we recommend the following readings and videos:

• The book “Chemistry: the central science” by Brown, LeMay and Bursten
• The page about bases on Khan Academy (https://en.khanacademy.org/science/chemistry/acids-and-bases-topic)
• The video “Bases: Properties and Identification” available on YouTube in the channel Chemistry by Prof. Paulo Valim.
• The video “What is pH and pOH?”, which is available on YouTube in the Science in Action channel.

Keep in mind that a complete understanding of bases goes beyond simply memorising concepts: students need to comprehend how these substances function and behave, both theoretically and practically.

Practical Activity: Exploring the World of Bases

Objective of the Project

The objective of this project is to conduct a practical experiment that allows the students to explore the chemistry of bases. Through this activity, students will be able to test different substances, analyse their behaviour and identify which ones are bases, as well as classify them according to their properties. Additionally, the students will have the opportunity to review safety issues when conducting practical activities involving chemical compounds, and will learn about neutralisation, one of the most important concepts in the study of bases.

This activity was designed to be conducted in groups of 3 to 5 students, and it is estimated that more than twelve hours of work will be necessary for each student.

Detailed Description of the Project

The project will be divided into three parts:

1. Study - where students will have to conduct research and understand the theory about bases, their properties, and classification methods, as well as neutralisation reactions.

2. Practical - students will prepare solutions of different substances, test them using indicators and classify them as acids, bases or neutral. Then, they will conduct neutralisation reactions and observe the results.

3. Report - students will prepare a detailed report about the entire project, discussing theories, the experiments they conducted, the results they obtained, and the conclusions they reached.

Necessary Materials

• Safety goggles and gloves
• Different substances for testing (for example: vinegar, lemon juice, baking soda, soap, ammonia)
• pH indicator (litmus paper or universal indicator)
• Beakers
• Burettes or syringes to accurately measure volumes
• Graduated cylinder
• Scale
• Distilled water

Detailed Step-by-Step Guide

1. After understanding the theory, students will start with a clean bench, using safety gear.

2. The students will weigh and prepare a solution of each of the substances that will be tested, dissolving them in water.

3. After preparing the solutions, students will test each of them using the pH indicator, and note down the result.

4. Based on the results they obtained, the students will classify the solutions as acids, bases or neutral substances.

5. Students will choose an acid and a basic solution, and they will conduct a neutralisation reaction, adding the acid solution to the basic solution gradually, and measuring the pH at each step to observe the change.

6. After conducting all the experiments, students will discuss the results and start working on the report.

Project Deliveries and Connection to the Activity

To conclude this project, each group must deliver a detailed report which includes an introduction on the subject that was studied, the development of the project, the conclusions, and the references that were used.

The report must be complete and must be able to demonstrate the groups’ understanding of the content that was covered during the project, as well as the results that were obtained during the practical activity, and the resulting conclusions.

• During the Introduction, students must contextualise the subject, showing how it is relevant and how it is used in the real world, as well as explaining the objective of the project.

• During the Development, students must discuss the theory behind bases, explain the activity they conducted in detail, the methodology they used, and the results they obtained.

• During the Conclusion, students must recap the main points of the project, explaining what they learned and what conclusions they were able to reach based on the project.

• During the References, students must indicate the sources they used for guidance during the project, such as books, web pages, videos, etc.

This project aims to be active and engaging, allowing students to put their knowledge into practice, work as a team, deal with time management and develop problem-solving and creative-thinking skills.