Contextualization

Theoretical Introduction

Common Concentration, also known as Mass Concentration, is a crucial part of the chemistry we study. It indicates how the quantities of solute and solution are related. It is usually expressed in g/L (grams per liter), and its calculation is done by dividing the mass of the solute (in grams) by the volume of the solution (in liters).

In chemistry, concentration is used to express how much of a substance (the solute) is present in a certain amount of another substance (the solvent). In a solution, the relationship between the amount of solute and the amount of solvent is called solution concentration.

Understanding common concentrations is crucial in chemical experimentation, where it is very important to know how much of a certain substance is present in a mixture. This allows scientists to predict and control the reactions that occur between different substances.

Contextualization and Importance

This concept has several practical applications. In the pharmaceutical industry, for example, understanding the concentration of a medication is crucial to ensure its therapeutic effectiveness and safety. In industrial processes, such as food production, the concentration of a particular ingredient can influence not only the taste of the final product but also its texture, color, and durability.

Another example of applying this knowledge is in the treatment of water for human consumption. By controlling the concentration of chlorine, it is possible to ensure that the water is free of health-harmful microorganisms, but without posing risks to the consumer.

Practical Activity: "Calculating Common Concentration in Practice"

Project Objective

The objective of this activity is for students to apply in practice, in groups of 3 to 5 people, the concept of common concentration, calculating the concentration of a solute in a solution.

Project Description

The groups will carry out an experiment in which they will prepare a sugar solution in water, at different concentrations, and measure the concentration of the solute using a scale and a measuring container. At the end of the experiment, students should present a detailed report, presenting and discussing the results obtained.

Necessary Materials

• Granulated sugar
• Measuring containers (beakers or measuring cups)
• Precision scale (0.1g)
• Drinking water
• Mixing spoons
• Stopwatch

Activity Step by Step

1. Each group should weigh 10g, 20g, and 30g of sugar, using the scale.
2. The groups should prepare three different solutions, dissolving each of the sugar masses in 100ml, 250ml, and 500ml of water, respectively. To do this, they should use the measuring containers.
3. The groups will mix each solution, timing the time required for the complete dissolution of the sugar.
4. After the complete dissolution of the sugar, the groups should calculate the common concentration of the three solutions, using the formula: C = m / V, where C is the common concentration (g/L), m is the mass of the solute (g), and V is the volume of the solution (L).

Project Deliverables

Each group will have to submit a document written in the form of a report containing, but not limited to, four main topics: Introduction, Development, Conclusions, and Bibliography used. The report format should follow the following structure:

• Introduction: should contain a brief contextualization of the concept of common concentration, the importance of understanding it, and the objective of the experiment.

• Development: in this section, students will explain the concept of common concentration, describe the experimental procedure, the methodology used, and discuss the results obtained. Calculations performed to determine the common concentration of the solutions should be included.

• Conclusions: here, students will recap the main points of the project, express what they have learned, what difficulties they encountered and how they overcame them, and what conclusions could be drawn.

• Bibliography: in this section, groups should indicate all sources of information used for the report.

This activity is expected to last one week, with an estimated time of five to ten hours of work per student, depending on the group size.