Objectives (5 - 10 minutes)

Main Objectives:

1. Introduce the concept of molality and its importance in Chemistry, highlighting its use in calculations involving colligative properties.
2. Develop students' ability to calculate molality in different situations, using the formula and understanding the concept.
3. Apply molality in practical examples, so that students understand its relevance and applicability in the real world.

Secondary Objectives:

1. Encourage active participation of students, whether through questions, discussions, or group problem-solving.
2. Stimulate critical thinking and problem-solving skills, essential for understanding and applying the concepts of molality.
3. Foster students' curiosity, encouraging them to explore more about the topic beyond what is presented in the classroom.

Introduction (10 - 15 minutes)

1. Review of previous concepts:

   • The teacher will start the class by quickly reviewing the concepts of solutions, solute, solvent, and concentration. These concepts are fundamental for understanding molality, and the review will help prepare students for the new content.
   • The use of practical examples during the review is suggested to facilitate understanding and retention of the concepts.

2. Problem situations:

   • The teacher can propose two hypothetical situations to arouse students' interest and introduce the need for a new concept. For example, 'How would we calculate the amount of substance needed to prepare a hydrochloric acid solution with a concentration of 2 mol/kg? And if we wanted to prepare the same solution, but with a different amount of solvent, how would that affect the amount of solute we would need?'
   • Another situation could be: 'Imagine you are a chemist responsible for preparing a saline solution with a concentration of 0.9 mol/kg. How do you calculate the exact amount of solute that should be added to the solvent?'

3. Contextualization:

   • The teacher will contextualize the importance of molality, showing how it is used in various everyday applications and in different fields of science. For example, in the preparation of medications, in the food industry, in beverage production, etc.
   • Another way to contextualize would be to present how molality is used in scientific research, for example, in determining the concentration of ions in solutions and in the analysis of dissolution processes.

4. Introduction to the topic:

   • The teacher can start the topic Introduction with curiosities or interesting facts about molality. For example, 'Did you know that molality is one of several ways to express the concentration of a solution, being the most direct and precise?' or 'Have you ever wondered why cooking recipes ask for a 'pinch' of salt instead of an exact amount? This is because most recipes are prepared in solutions, where the concentration of each ingredient is crucial for the final flavor of the dish.'
   • The teacher can also present a real problem involving molality, such as determining the concentration of salt in seawater and its impact on marine life. This can help spark students' interest and demonstrate the relevance of the topic.

Development (20 - 25 minutes)

1. Activity 'Solving the solution mystery':

   • The teacher will divide the class into groups of up to five students and provide each group with a set of materials: two solid substances (A and B), two identical containers, water, and a scale.
   • The teacher will explain that each group will receive a letter from a 'mysterious scientist' describing a situation. The letter will say: 'To create a solution with a concentration of 3 mol/kg, add 4 g of substance A to 500 g of water in one container. In another container, add 5 g of substance B to 400 g of water. But be careful! If you use the wrong amount of solute or solvent, the solution will not have the correct concentration!'
   • The challenge for the groups will be to determine the molarity of each of the solutions described in the letter and use this knowledge to find out which substance is A and which is B.
   • Students should weigh substances A and B, measure the amount of water, and calculate the molarity of each solution. They should also calculate the amount of solute and solvent that the 'mysterious scientist' used in each container.
   • The group that correctly identifies the molarity of each solution and the identity of substances A and B will be the winner.
   • During the activity, the teacher will circulate around the room, guiding the groups and clarifying any doubts.

2. Activity 'Molality in everyday life':

   • The teacher will then propose an activity in which groups will create scenarios from everyday life involving molality.
   • Each group should create a scenario and propose a question that involves calculating molality. For example, 'Imagine you are preparing tea and need to calculate the exact amount of sugar that should be dissolved in water to obtain a molality of 0.5 mol/kg. How would you make this calculation?' or 'You are preparing a fertilizer solution for your plants. The fertilizer packaging states that the molality of the solution should be 2.5 mol/kg. How would you determine the amount of fertilizer and the amount of water needed to prepare the solution?'
   • Each group should present its situation and question to the class, which will try to solve the proposed problem. The teacher will guide the discussion and check students' understanding of the subject.

3. Activity 'Molality in experiments':

   • To conclude the Development stage, the teacher will propose a practical experiment in which students will have the opportunity to apply the concept of molality in practice.
   • The experiment could be the preparation of a solution of specific concentration, with students having to calculate the amount of solute needed and measure the amount of solvent.
   • During the experiment, the teacher will guide the students, explaining the procedure and reinforcing the importance of molality for the correct execution of the experiment.
   • At the end of the experiment, students will have the chance to compare the solution they prepared with a solution of known concentration, verifying if they achieved the desired molality.

Return (10 - 15 minutes)

1. Group discussion (5 - 7 minutes):

   • The teacher will ask each group to share their solutions or conclusions from the activities 'Solving the solution mystery' and 'Molality in everyday life'. Each group will have up to 3 minutes to make their presentation.
   • During the presentations, the teacher will intervene, asking questions to ensure that all students understand the solutions proposed by each group. This will also serve to clarify any concepts that may have been misunderstood.
   • The teacher will also encourage other groups to ask questions and make comments about their classmates' presentations, thus promoting interaction among students and the collective construction of knowledge.

2. Connection with theory (3 - 5 minutes):

   • After all presentations, the teacher will summarize the main ideas discussed, relating them to the theory presented at the beginning of the class.
   • The teacher will highlight how molality was used to solve the problems proposed in the activities and how it is applied in real-life situations and in the industry.
   • The teacher will also take this opportunity to clarify any remaining doubts and to reinforce the most important concepts.

3. Individual reflection (2 - 3 minutes):

   • To conclude the class, the teacher will propose that students reflect for one minute on three questions:
     1. What was the most important concept learned today?
     2. What questions have not been answered yet?
     3. How can molality be applied in other everyday situations or in other disciplines?
   • The teacher will encourage students to write down their reflections so they can review them later and use them as a starting point for the next class or for content review in future classes.
   • The teacher may also ask students to share their reflections, if they feel comfortable, as a way to promote metacognition and students' understanding of their own learning process.

Conclusion (5 - 10 minutes)

1. Recapitulation and Synthesis (2 - 3 minutes):

   • The teacher should start the Conclusion by recapitulating the main points discussed during the class. This includes defining molality, recalling the calculation formula, and highlighting its importance in Chemistry and practical applications.
   • The teacher should also reinforce the key concepts learned, such as the relationship between the amount of solute and solvent and the concentration of a solution, and how molality is a precise measure of this concentration.
   • Synthesis is an important moment for the teacher to verify if the Learning Objectives were achieved and for students to consolidate what they have learned.

2. Connection between theory, practice, and applications (1 - 2 minutes):

   • The teacher should highlight how the class connected theory (concepts and formulas) with practice (activities and experiment) and with applications (everyday situations and in different fields of science).
   • The teacher can review the practical examples and activities carried out, explaining how they helped illustrate the application of molality and how they allowed students to practice calculation and problem-solving.
   • Additionally, the teacher can reinforce how molality is an essential tool in many areas of science and industry, from food and drug preparation to scientific research and industrial production.

3. Supplementary Materials (1 - 2 minutes):

   • The teacher should suggest additional materials for students who wish to deepen their knowledge of molality. This may include textbooks, educational videos, chemistry websites, and online practice exercises.
   • For example, the teacher may suggest that students watch a video explaining molality in a different way, or read a chapter in a chemistry book that explains in more detail how to calculate molality.
   • These supplementary materials will not only help students consolidate what they have learned but also allow them to expand their knowledge and understanding of the topic.

4. Relevance of the topic to everyday life (1 - 2 minutes):

   • To conclude the class, the teacher should reinforce the relevance of molality to students' daily lives.
   • For example, the teacher may mention that molality is used in food preparation, drug production, chemical solution analysis, and even in beverage preparation.
   • Additionally, the teacher can emphasize that the ability to understand and use molality is an important skill for anyone wishing to work in a field related to science, technology, engineering, or mathematics.