Objectives (5 - 7 minutes)

1. Understand the concept of Phase Diagrams: students should be able to define and explain what a phase diagram is, identifying the different phases of a substance and understanding how they change with variations in temperature and pressure.

2. Analyze and interpret Phase Diagrams: students should acquire skills to analyze and interpret phase diagrams, identifying changes in physical states and the associated pressure and temperature conditions.

3. Apply the knowledge of Phase Diagrams: students should be able to apply the acquired knowledge about phase diagrams to solve problems and answer questions about changes in physical states and the necessary conditions for these changes.

Secondary Objectives:

• Develop critical thinking and problem-solving skills: Students should be encouraged to think critically and apply the acquired knowledge to solve complex problems related to phase diagrams.

• Stimulate active participation and collaboration: Through practical activities and classroom discussions, students should be encouraged to actively participate in the class and collaborate with their peers to enhance their understanding of the subject.

Introduction (10 - 12 minutes)

1. Review of previous concepts: The teacher should start the lesson by reviewing the concepts of the physical states of matter (solid, liquid, and gas), as well as the changes in physical states (melting, solidification, vaporization, condensation, and sublimation). This is essential for understanding the topic at hand.

2. Problem situations:

   • The teacher can propose the following situation: 'Imagine you have an ice cube in a glass. What happens to the ice when you place the glass in the sun? And if you put the glass in the freezer? Why does this happen?' This situation serves to stimulate students' curiosity and introduce the concept of phase change of a substance according to temperature and pressure.

   • Another situation that can be proposed is: 'If you have a pressure cooker with water, what happens to the water when you heat it? What happens when you release the pressure from the cooker?' This situation addresses the influence of pressure on the phase change of a substance.

3. Contextualization: The teacher should emphasize the importance of the topic, explaining that understanding phase diagrams is fundamental in various areas, such as engineering (for example, in the design of boilers and chemical reactors), meteorology (to understand the water cycle in the atmosphere), and even in cooking (by understanding how pressure and temperature affect food cooking).

4. Introduction to the topic:

   • The teacher can start the Introduction by telling the story of how the concept of phase diagrams was developed. For example, they can mention the contributions of Benjamin Thompson, Lord Kelvin, Josiah Willard Gibbs, and other scientists to the understanding of phase changes.

   • Next, the teacher should explain that the phase diagram is a graphical representation that illustrates the different phases of a substance and the temperature and pressure conditions under which these phases coexist.

5. Lesson Objectives: Finally, the teacher should present the Lesson Objectives, which are to understand the concept of phase diagrams, analyze and interpret phase diagrams, and apply this knowledge to solve problems related to phase changes of matter.

Development (20 - 25 minutes)

1. Practical Activity - 'Building a Phase Diagram' (10 - 12 minutes)

   • Materials needed: Plasticine of various colors, cardboard paper, colored pens, and scissors.

   • Step by step:

     1. The teacher should divide the class into groups of 4 to 5 students and provide each group with the necessary materials.

     2. Each group should mold three different shapes with the plasticine, representing the solid, liquid, and gas phases of a substance.

     3. Then, the students should glue the plasticine shapes on the cardboard paper, forming a 'Phase Diagram'.

     4. Using the colored pens, the students should draw arrows to show the phase changes that occur when temperature or pressure changes.

     5. The students should discuss and decide which arrows to draw and in which direction, based on their understanding of the topic. The teacher should move around the room, guiding and clarifying doubts.

     6. After completing the diagram, each group should present their work to the class, explaining what each part of the diagram represents and why they chose to draw the arrows that way.

     7. The teacher should draw connections between the diagrams made by the students and the real phase diagrams that will be discussed in the next activity.

2. Discussion Activity - 'Interpreting Real Phase Diagrams' (10 - 12 minutes)

   • Materials needed: Images of real phase diagrams (e.g., the water phase diagram) and a list of discussion questions.

   • Step by step:

     1. The teacher should show the students the images of the phase diagrams and explain what each part of the diagram represents.

     2. Then, the teacher should divide the class into small groups and provide each group with an image of a different phase diagram.

     3. Using the list of questions as a guide, the students should discuss in their groups what the diagram represents, which phases are present, and under what temperature and pressure conditions these phases coexist.

     4. The teacher should move around the room, listening to the discussions and clarifying doubts.

     5. After a set time, each group should present their diagram and conclusions to the class.

     6. The teacher should lead a class discussion, comparing the different diagrams and highlighting the main points.

   • Example discussion questions:

     1. 'Which phases are present in this diagram and under what temperature and pressure conditions do they coexist?'

     2. 'What happens to the substance when the temperature or pressure changes?'

     3. 'Why are some phases stable under certain conditions and others are not?'

     4. 'How can you tell if a phase change is exothermic or endothermic from the diagram?'

     5. 'How does the phase diagram relate to the substance's real-life behavior?'

Return (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes)

   • The teacher should facilitate a group discussion with all students, where each group will have up to 3 minutes to share the solutions or conclusions they reached during the practical and discussion activities.

   • The goal of this stage is for students to learn from each other, hearing different interpretations of the phase diagrams and how they relate to phase changes of matter.

   • The teacher should encourage students to ask questions and make comments about the presentations of other groups, promoting a collaborative learning environment.

2. Relation to Theory (2 - 3 minutes)

   • After the group presentations, the teacher should provide a quick review of the theoretical concepts discussed during the lesson and relate them to the solutions presented by the students.

   • The teacher should highlight how the practical activities helped illustrate and deepen students' understanding of phase diagrams.

3. Individual Reflection (3 - 4 minutes)

   • Finally, the teacher should suggest that students reflect individually on what they learned during the lesson, mentally answering questions such as:

     1. 'What was the most important concept I learned today about phase diagrams?'

     2. 'What questions have not been answered yet?'

   • The teacher should encourage students to share their answers with the class, promoting an open and respectful learning environment.

   • The teacher should also collect the students' responses, either through a classroom discussion, an online questionnaire, or a written assignment to assess students' understanding of the lesson topic.

4. Closure

   • To conclude the lesson, the teacher should emphasize the importance of understanding phase diagrams for comprehending the behavior of matter under different temperature and pressure conditions.

   • The teacher should thank the students for their active participation and encourage them to continue studying the subject and to ask questions whenever they have doubts.