Context

Stoichiometry is a fundamental concept in chemistry that deals with the relationships between the quantities of reactants and products involved in a chemical reaction. It is called 'the art of counting atoms'. In this sense, stoichiometry allows us to calculate the amount of a reactant that is needed to react with a given amount of another reactant, or the amount of a product that will be produced from a given amount of reactant.

Stoichiometry is based on two fundamental laws: the Law of Conservation of Mass, which states that matter cannot be created nor destroyed, and the Law of Definite Proportions, which establishes that a specific chemical substance always contains the same elements in the same mass proportions. These laws are the basis of stoichiometry and allow us to make accurate predictions about the quantities of reactants and products in a chemical reaction.

It is important to note that stoichiometry is only valid for reactions that actually occur. Some reactions that we can write according to the laws of chemistry do not occur in practice because they require conditions that we cannot achieve or because the reaction is too slow. However, for the reactions that we can make happen, stoichiometry is a powerful tool that allows us to predict the results.

Stoichiometry is the backbone of chemistry and is used in a variety of applications, such as in the industrial production of chemical compounds, pollution control, materials science, and many other areas of science and engineering. For example, stoichiometry allows us to calculate the exact amount of reactants needed to produce a certain amount of product, which is vital for the efficiency and profitability of industrial production.

Furthermore, stoichiometry also has everyday applications that we may not realize. For example, when we cook, we perform a series of chemical reactions and the result can depend greatly on the proportions of the ingredients we use - a clear example of stoichiometry in action!

Here are some reliable sources you can use to delve deeper into the subject:

1. Khan Academy, Stoichiometry: Khan Academy
2. Brasil Escola, Stoichiometry: Brasil Escola
3. Mundo Educação, Stoichiometry: Mundo Educação

Practical Activity

Activity Title: 'The Chemistry in the Kitchen: The Stoichiometry of Cake'

Project Objective:

This project challenges students to apply the principles of stoichiometry to calculate the correct proportions of the ingredients in a cake recipe. Students will adjust the recipe for different numbers of servings, ensuring that the correct ingredient proportions are maintained.

Detailed Project Description:

In groups of 3 to 5 people, students will choose a cake recipe and then apply stoichiometric principles to adjust it for a different number of servings - either scaling up to serve a large party, or scaling down to serve just a few friends. Students will document the entire process, from choosing the recipe, calculating and executing the new recipe, to drawing conclusions.

Required Materials:

• A cake recipe
• Ingredients needed to make the cake
• Calculator
• Basic kitchen utensils (e.g., bowls, spoons, mixer, oven, etc.)

Detailed Step-by-Step for Activity Execution:

1. Choose a cake recipe: Your group should choose a cake recipe and list all the ingredients and their quantities needed for the original servings.

2. Adjust the recipe: Your group will decide how many people they want to make the cake for now. Use stoichiometric principles to calibrate the recipe for this new number of servings. For example, if the original recipe is for 8 servings and your group wants to make it for 16 people, then all ingredients should be doubled.

3. Make the cake: Now, follow the adjusted recipe and make the cake. Document the process with photos and remember to note any difficulties or observations during the process.

4. Project Report: Finally, your group will write a detailed report on the project. This report should include the following topics:

   a. Introduction: Why did you choose this recipe? How many servings does the original recipe make and for how many people did you adjust it? What is the practical relevance of stoichiometry based on this project?

   b. Development: Here you should explain the stoichiometry theory used to adjust the recipe, explain each step of the activity in detail, present the methodology used. You should also present and discuss the results obtained, showing how stoichiometry was applied in practice.

   c. Conclusion: What did your group learn from this project? What was the most difficult/easiest part? What would you do differently if you could start over? What conclusions did you draw about the importance of stoichiometry in everyday life?

   d. Bibliography: List all the sources you used for the project, including books, websites, videos, etc.

This project should take two to four hours per student to complete and has a one-week deadline.