Contextualization

Bases are substances that have the property of donating electron pairs. They can be recognized because they are able to react with acids, forming a salt and water in a known neutralization reaction. In addition, they are bitter, slippery to the touch and change the color of certain specific indicators, such as phenolphthalein and litmus paper, for example.

Historically, it was the Arab alchemists who began the systematic study of bases. They observed that certain substances, such as quicklime, could neutralize the effects of acids. This evolved until we arrived at the definition of bases that we have today, much more sophisticated and based on experimental evidence.

Bases are also especially important in everyday life, both for maintaining life and in industrial processes. Our blood is a buffered solution: this means that it can resist sudden changes in pH due to the presence of substances that can act as acids or bases, depending on the case. In addition, bases are used in the manufacture of soaps, in the neutralization of acid spills and in various other chemical processes.

Theoretical Introduction

The study of bases challenges us to think about how molecules interact with each other, and how these interactions lead to the phenomena that we observe every day. This allows us to understand the principles that govern the universe on a very small scale, and this understanding is fundamental for us to be able to control and direct these interactions in our favor.

Bases are divided into two main categories: Arrhenius bases and Brønsted-Lowry bases. The Arrhenius definition is more restricted and only counts as a base the substances that, when dissolved in water, release the OH- ion. The Brønsted-Lowry definition is more general, and counts as a base any substance capable of receiving a proton.

Lewis's theory is even more comprehensive and defines as a base any chemical species that donates an electron pair. This definition is the most used today, as it allows us to explain a wider variety of reactions.

Practical Activity - "Soap Base"

Project Objective

The objective of this project is the home production of soap, exploring the concept of neutralization between acid and base. With this activity, students are expected to:

• Understand the chemistry involved in soap production;
• Relate theoretical study to practice, observing the direct application of academic knowledge in everyday life;
• Develop teamwork, time management and problem solving skills.

Detailed Project Description

In this project, students will work in groups of 3 to 5 people. They will have one week to produce the soap, perform verification tests and produce a report on the activities.

The steps involve collecting used oil (acidic source), neutralizing it with a base (caustic soda), producing the soap, and finally verifying its quality through simple tests.

Required Materials

• 500 ml of used cooking oil
• 100 g of caustic soda (NaOH)
• 180 ml of water
• 20 ml of ethyl alcohol (ethanol)
• A plastic container (do not use aluminum) to make the mixture
• Wooden spoon
• Molds to shape the soap
• Gloves and protective glasses

Caustic soda can be dangerous. Always handle with care, wearing gloves and goggles and in a ventilated environment.

Step by Step

1. Put the water in a plastic container.
2. Add the caustic soda and stir until dissolved. Beware of vapors.
3. Add the oil gradually, stirring constantly.
4. Add ethyl alcohol.
5. Continue stirring for about 40 minutes until the mixture starts to thicken.
6. Pour the mixture into the molds and let it dry for 24 hours.
7. Once dry, remove the soap from the molds.

Project Deliverables

At the end of the soap production, students must prepare a report that will be divided into four parts:

1. Introduction: Explain the importance of bases in soap production and its impact on everyday life.

2. Development: Describe in detail each step of the soap production process. Explain the chemical reaction that occurred between the acid (oil) and the base (caustic soda) that resulted in the formation of the soap. Discuss the results obtained, such as appearance and solubility of the soap produced.

3. Conclusion: Review the main points constructed during the project, explaining the lessons learned, the difficulties encountered during the soap production and the conclusions drawn about the practice of soap production.

4. Bibliography: Cite the research sources used during the project.

It is important to remember that each step must be documented with photos, forming a kind of project diary, which can be included in the final report.