Objectives (5 - 7 minutes)

1. Understand the concept of enthalpy and its importance in thermochemistry.
2. Develop skills to calculate and interpret the enthalpy change in chemical reactions.
3. Practice the practical application of enthalpy in different contexts and chemical reactions.

Secondary Objectives:

• Stimulate active participation of students in discussions and proposed activities.
• Encourage research and autonomous study on the subject.
• Promote understanding of the importance of thermochemistry in everyday life.

Introduction (10 - 15 minutes)

1. Review of previous concepts: The teacher starts the class by briefly reviewing the concepts of chemical reactions and energy. He may remind students about the laws of conservation of energy, Hess's law, and Kirchhoff's law, which are fundamental for understanding enthalpy. (3 - 5 minutes)

2. Problem situations: The teacher proposes two problem situations to arouse students' interest. The first one could be: 'Why does a combustion reaction release heat?' and the second one: 'Why does a boiled egg cool down when placed in a glass of cold water?'. These questions aim to stimulate students to think about the transfer of energy in chemical reactions. (2 - 3 minutes)

3. Contextualization: The teacher then contextualizes the importance of enthalpy, explaining how it is applied in various areas, such as the food industry, energy production, medicine, among others. He can cite examples, such as the use of enthalpy to calculate the amount of energy released in an explosion, or to understand how the human body converts food energy into work. (2 - 3 minutes)

4. Engaging students' attention: To arouse students' curiosity, the teacher can share some curiosities about enthalpy. For example, he can mention that the enthalpy of formation of simple substances, such as hydrogen and oxygen, is defined as zero, and that the enthalpy of formation of a compound is the amount of energy released or absorbed when that substance is formed from its constituent elements, under standard conditions. Another interesting curiosity is that the enthalpy of a chemical reaction can be negative (exothermic) or positive (endothermic), depending on whether the reaction releases or absorbs energy, respectively. (3 - 4 minutes)

Development (20 - 25 minutes)

Activity 1: 'Understanding Enthalpy with Lego' (10 - 12 minutes)

1. Preparation: The teacher organizes students into groups of 4 or 5 and distributes a Lego kit to each group. The kits should contain the same types and quantities of pieces, but in different colors. The teacher also hands out activity cards that contain a series of hypothetical chemical reactions for students to model with Lego. Each card should indicate the types and quantities of Lego pieces needed to model the reaction.

2. Execution: The students, in their groups, choose an activity card and start building the reaction with the Lego pieces, following the instructions on the card. They should discuss and decide together which Lego pieces will represent the reactants and products of the reaction. The teacher circulates around the room, observing and guiding the groups as needed.

3. Discussion: After completing the modeling of the reaction, students should discuss in their groups how the reaction occurred, which pieces 'broke' and which 'joined' to form the products. They should also discuss whether the reaction released or absorbed energy, and why. The teacher should facilitate the discussion, clarifying doubts and reinforcing the concepts of enthalpy.

Activity 2: 'Enthalpy Game' (10 - 12 minutes)

1. Preparation: The teacher prepares an enthalpy board game, where each square represents a step in a chemical reaction. The squares may contain questions about enthalpy, which students must answer correctly to advance in the game. The teacher divides the students into pairs and gives each pair a set of tokens in different colors, which will be used to move around the board.

2. Execution: The pairs take turns playing, rolling a die and moving their tokens on the board according to the number obtained on the die. When a pair lands on a square, the teacher asks a question about enthalpy. If the pair answers correctly, they advance, otherwise, they stay on the same square. The goal of the game is to reach the last square on the board first.

3. Discussion: After finishing the game, students discuss in their pairs about the most difficult questions and the strategies they used to advance in the game. The teacher should take advantage of this discussion to reinforce the concepts of enthalpy and clarify any remaining doubts.

Activity 3: 'Simulating Reactions with PhET' (5 - 8 minutes)

1. Preparation: The teacher instructs students to access the PhET website (phet.colorado.edu) on their mobile devices or computers.

2. Execution: Students explore the 'Reactions and Enthalpy' simulation on the PhET website, where they can perform virtual chemical reactions and observe the enthalpy of the reaction. They should choose some reactions to simulate and note the enthalpy of each one.

3. Discussion: After exploring the simulation, students discuss in their groups about the reactions they simulated and the enthalpies they observed. The teacher should guide the discussion, clarifying doubts and highlighting the main points.

These activities aim to provide students with a practical and playful understanding of the concept of enthalpy, as well as develop their problem-solving skills and teamwork.

Return (8 - 10 minutes)

1. Group Discussion: The teacher gathers all students and promotes a group discussion about the solutions or conclusions reached by each group during the activities. Each group has up to 3 minutes to share their ideas, while the other groups listen and take notes. (3 - 4 minutes)

2. Connection to Theory: After all presentations, the teacher reviews the theoretical concepts discussed at the beginning of the class and makes connections with the solutions or conclusions presented by the groups. For example, he can highlight how enthalpy was applied in modeling reactions with Lego, or how the concepts of enthalpy helped solve the questions in the Enthalpy Game. (2 - 3 minutes)

3. Individual Reflection: The teacher proposes that students reflect individually for a minute on what they learned in today's class. He can ask some questions to guide the reflection, such as: 'What was the most important concept you learned today?' and 'What questions have not been answered yet?'. Students can write down their reflections in a notebook or an online questionnaire. (1 - 2 minutes)

4. Feedback and Closure: The teacher asks for feedback from students about the class, asking what they liked and found challenging. He can also ask for suggestions for improvements for future classes. The teacher thanks everyone for their participation and ends the class, reinforcing the importance of continuous study and practice for understanding enthalpy. (1 minute)

This Return moment is essential to consolidate students' learning, allow them to reflect on what they have learned, and identify any doubts or gaps in their understanding. Additionally, it provides valuable feedback to the teacher to enhance his future classes.

Conclusion (5 - 7 minutes)

1. Recapitulation: The teacher starts the Conclusion of the class by summarizing the main points covered, recalling the concepts of enthalpy, endothermic and exothermic reactions, and the importance of enthalpy in thermochemistry. He can also briefly review the practical activities carried out, highlighting the most significant discoveries made by the students. (2 - 3 minutes)

2. Theory-Practice Connection: Next, the teacher connects the presented theory with the practical activities carried out. For instance, he can explain how modeling reactions with Lego helped visualize the transfer of energy in a chemical reaction, and how the Enthalpy Game allowed the application of theoretical concepts in a fun and challenging way. He can also emphasize how simulating reactions on PhET allowed exploring enthalpy in an interactive and realistic manner. (1 - 2 minutes)

3. Extra Materials: The teacher then suggests some extra materials for students to deepen their understanding of enthalpy. These may include educational videos from YouTube, interactive online simulations, chemistry websites with detailed explanations, and enthalpy problems to solve. For example, he may suggest the video 'What is Enthalpy?' from the 'Khan Academy' channel and the 'Reactions and Enthalpy' simulation from the PhET website. (1 minute)

4. Practical Applications: Finally, the teacher highlights the practical importance of enthalpy, mentioning some of its applications in daily life and in various areas of science and industry. He can cite examples, such as the use of enthalpy to calculate the efficiency of a fuel, to understand how living organisms convert food energy into work, or to predict the final temperature of a mixture of substances. He can also encourage students to think about other situations where enthalpy could be useful. (1 minute)

The Conclusion of the class is an essential step to consolidate students' learning, reinforce key concepts, and motivate them to continue studying the topic. By connecting theory with practice and applications, and by providing extra materials for autonomous study, the teacher helps solidify students' understanding of enthalpy and thermochemistry.