Contextualization

In this first part, we will work with the concept of Dilution, a fundamental principle of chemistry that you have probably already used in your daily life, even without realizing it. But what does diluting a solution mean? In a simple approach, diluting a solution means decreasing its concentration by adding a solvent.

Dilution is a process widely used in laboratories and industries, and also quite common in our daily lives. It happens when we want to decrease the concentration of a solute in a certain solution. This is done by adding more solvent to the solution, without adding more solute. The resulting solution (the mixture of the solute with the solvent) has a lower concentration than the original solution.

Calculating the final concentration of a diluted solution is an essential skill in chemistry. The concept of dilution is the basis for understanding the preparation of solutions and their concentration calculations. And that's exactly what we will focus on in our project!

How is the concept of dilution applied in real life? In many areas! In medicine, for example, medications are diluted to achieve the correct dosage. In cooking, we dilute juices and broths. In the industry, dilution is used to adjust the concentration of chemicals in manufacturing processes.

Some reliable sources for consultation and further study on the subject are:

• Book: ATKINS, P.; JONES, L. Principles of Chemistry: Questioning modern life and the environment. 5th ed., Porto Alegre: Bookman, 2012.

• Website: Brasil Escola, Chemistry section Dilution of Solutions.

• Video: Dilution of Solutions - Easy Chemistry available on YouTube.

Practical Activity

Activity Title: "The Art of Dilution: A Visual Experiment"

Project Objective:

This project aims to understand the concept of chemical dilution in a practical way, using the coloring of solutions to visualize the phenomenon. Additionally, it seeks to develop collaboration skills, time management, and scientific thinking.

Detailed Project Description:

Students, divided into groups of 3 to 5 people, must create a sequence of dilutions with a food coloring. Initially, students should plan the process, considering how many dilutions they intend to perform and what will be the proportion of solvent that will be added at each stage.

Then, the groups must carry out the dilution and record the entire process in a video format. The dilution must be done carefully, always noting the proportion of coloring and solvent used.

Finally, the groups must prepare a report, explaining the experiment carried out, the decisions made, the dilution calculations performed, and what they observed at the end of the process, as well as discussing the concepts involved in the activity.

Required Materials:

• Strongly colored food coloring (e.g., blue or red).
• Water (which will be our solvent).
• Transparent disposable cups.
• Screens of different volumes for measurements.
• Camera for recording the experiment.

Detailed Step-by-Step:

1. Gather the group and discuss the activity. Plan how many dilutions you intend to perform and what will be the proportion of solvent added at each stage.

2. In the first cup, place a predefined amount of food coloring (e.g., 10 mL) and note the amount.

3. Add the same amount of water to the cup and mix well. Note the amount of water added.

4. Take a predefined amount of the diluted solution (e.g., 10 mL) and place it in a new cup. Note the amount taken.

5. To the new cup, add the same amount of water and mix.

6. Repeat steps 4 and 5 for the next dilution stages, always noting the amounts of coloring and water used.

7. In the end, students should have a sequence of cups with coloring solutions, whose coloration should progressively become weaker at each stage. Make a video showing the sequence of cups and the difference in color.

8. Based on the notes of the amounts of coloring and water used, calculate the concentration of the solution at each stage of dilution.

9. Prepare the final project report. In this report, describe the experiment carried out, the decisions made, the dilution calculations, and what was observed. Also discuss the theory of dilution and the practical implications of this concept.

Project Deliverables:

Groups must deliver the dilution experiment video and the final report. It is important to remember that the completion of the experiments and the writing of the report take time, so it is necessary for the groups to organize themselves so that they can carry out all activities within the stipulated one-week deadline. The report should follow the suggested format: Introduction (contextualization and objectives); Development (description of the experiment, decisions made, dilution calculations, and observations); Conclusion (summary of the main points, learnings, and implications of the dilution concept); and Bibliography.