Objectives (5 - 7 minutes)

1. Understand the concept of vapor pressure and its relation to colligative properties, especially the effect of non-volatile solutes on the vapor pressure of a solvent.

2. Develop skills to calculate the variation in vapor pressure of a solvent using Raoult's law.

3. Apply the acquired knowledge to solve problems and practical situations related to vapor pressure and colligative properties, including calculating the vapor pressure of a solvent in a solution.

Secondary Objectives:

• Stimulate critical thinking and problem-solving skills through the practical application of acquired theoretical knowledge.

• Foster teamwork skills and collaboration through group practical activities.

Introduction (10 - 15 minutes)

1. Review of previous concepts: The teacher should start the class by reviewing the concepts of colligative properties and vapor pressure, which were studied in previous classes. This review can be done through a brief explanation and/or directed questions to evaluate students' prior knowledge. (3 - 5 minutes)

2. Problem situations: Next, the teacher should propose two problem situations to arouse students' interest and curiosity. The first one could be: 'Why does water take longer to boil when we add salt?' and the second: 'Why does a bicycle tire's pressure increase when we inflate the tire, but decrease when the bike is left in the sun?' The teacher should encourage students to think of possible explanations, even if they are not sure of the answers. (3 - 5 minutes)

3. Contextualization: The teacher should then explain the importance of studying vapor pressure and colligative properties, relating them to everyday situations and practical applications. For example, vapor pressure is crucial to understand why water takes longer to boil at high altitudes, and colligative properties are fundamental to the food industry, as many cooking and preservation processes depend on them. (2 - 3 minutes)

4. Introduction to the topic: Finally, the teacher should introduce the topic of vapor pressure in an engaging way. They can share some curiosities, such as the fact that water's vapor pressure decreases as the temperature decreases, explaining why water evaporates more quickly on a hot day than on a cold day. Another curiosity is that the vapor pressure of a pure substance is the pressure exerted by the vapors of that substance when it is in equilibrium with its liquid state. From these examples, the teacher should prompt students to think about how vapor pressure can be altered by the addition of a solute, which will be the focus of the lesson. (2 - 3 minutes)

Development (20 - 25 minutes)

1. Practical Activity 1: 'The race in the laboratory' (10 - 12 minutes)

   • The teacher should divide the class into groups of up to 5 students. Each group will receive a tray of ice and two identical coins, which will be placed on the ice.
   • The challenge is to make one of the coins fall on the ice before the other. Students should think of a strategy to achieve this.
   • After the students have discussed and proposed their strategies, the teacher should reveal that one of the coins was slightly salted before the activity began.
   • The objective of this activity is to illustrate the concept of vapor pressure, showing how the addition of a non-volatile solute (salt) can decrease the vapor pressure of the solvent (water), causing the ice to melt more slowly under the salted coin.

2. Practical Activity 2: 'The mystery of raindrops' (10 - 12 minutes)

   • Still in groups, students will receive two identical containers and a quantity of cotton. The teacher should ask students to wet the cotton in water and place it in one of the containers.
   • Next, students should cover both containers, one with a lid and the other with plastic wrap, which will be secured with a rubber band. Then, students should observe what happens to the water in the container over time.
   • In this activity, students will be exploring vapor pressure and boiling point. The water in the container with the cotton will evaporate more quickly due to the increased contact surface, creating a higher internal pressure. In the container with the plastic wrap, evaporation will be slower, resulting in a lower internal pressure. This will cause the water to condense more quickly inside the container, resembling raindrops.

3. Discussion and Results Analysis (5 - 7 minutes)

   • After the activities, the teacher should lead a classroom discussion, asking students to reflect on what they observed and how it relates to the concept of vapor pressure.
   • The teacher should then make the connection with the theory, explaining that the vapor pressure of a liquid depends on the number of particles in its gaseous state, and that the addition of a non-volatile solute decreases the vapor pressure of the solvent.

Return (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes)

   • The teacher should gather all students and start a group discussion. Each group will have up to 3 minutes to share their conclusions and solutions from the practical activities carried out.
   • During the presentations, the teacher should encourage students to ask questions and make comments, thus promoting a collaborative learning environment.

2. Connection with Theory (3 - 4 minutes)

   • After the group presentations, the teacher should connect the practical activities with the theory presented at the beginning of the class.
   • The teacher should highlight how the activities illustrated the effect of adding a non-volatile solute on the vapor pressure of a solvent, and how this relates to colligative properties.
   • The teacher should use this opportunity to clarify any remaining doubts and reinforce the key concepts of the lesson.

3. Individual Reflection (2 - 3 minutes)

   • Finally, the teacher should suggest that students reflect individually on what they have learned.
   • The teacher can ask questions like: 'What was the most important concept learned today?' and 'What questions have not been answered yet?'
   • The teacher should give students a minute to think about the answers and then may ask some students to share their reflections with the class.
   • This step is crucial for the consolidation of learning, as it allows students to internalize the concepts and identify any gaps in their understanding.

By the end of this stage, students should have a clear understanding of the vapor pressure concept and how colligative properties can be applied to calculate the variation in a solvent's vapor pressure. They should also have developed skills to solve problems and practical situations related to this topic.

Conclusion (5 - 7 minutes)

1. Content Summary (2 - 3 minutes)

   • The teacher should start the Conclusion stage by summarizing the main points of the lesson. They should review the concepts of vapor pressure and colligative properties, emphasizing the effect of adding a non-volatile solute on a solvent's vapor pressure.
   • For example, the teacher can highlight Raoult's Law, which states that the vapor pressure of a solvent in a solution is equal to the vapor pressure of the pure solvent multiplied by the solvent's molar fraction in the solution.
   • The goal of this recap is to consolidate the acquired knowledge, connecting the different elements of the lesson and reinforcing the most important concepts.

2. Connection between Theory, Practice, and Applications (1 - 2 minutes)

   • Next, the teacher should highlight how the lesson connected theory, practice, and applications. They should explain that the theory of vapor pressure and colligative properties was illustrated through the practical activities carried out.
   • The teacher can also emphasize how these concepts have important practical applications, such as in the food industry and in understanding natural phenomena like water evaporation and rain formation.

3. Additional Materials (1 minute)

   • The teacher should suggest extra materials for students to deepen their knowledge on the topic. These materials may include explanatory videos, chemistry websites, books, and scientific articles.
   • Some examples of materials that can be suggested are: the 'Crash Course Chemistry' series on YouTube, the 'Khan Academy' website, the book 'Principles of Chemistry' by Peter Atkins and Loretta Jones, and the scientific article 'Solute-solute and solute-solvent interactions in aqueous solutions of ethylene glycol and methanol' by S. S. Gupta and R. K. Jain.

4. Importance of the Topic in Daily Life (1 - 2 minutes)

   • Finally, the teacher should explain the relevance of the topic presented to students' daily lives. They can highlight, for example, how knowledge about vapor pressure and colligative properties can help understand everyday phenomena, such as why water takes longer to boil at high altitudes or why a bicycle tire's pressure increases when inflated.
   • The teacher can also mention how this knowledge can have practical applications in various areas, such as the pharmaceutical industry, the food industry, and meteorology.

By the end of this stage, students should have consolidated the acquired knowledge, understood the connection between theory, practice, and applications, identified resources to deepen their studies, and recognized the importance of the topic in their daily lives and in various application areas.