Lesson Plan | Active Learning | Thermochemistry: Enthalpy

Assumptions: This Active Lesson Plan assumes: a 100-minute class, prior student study with both the Book and the start of Project development, and that only one activity (among the three suggested) will be chosen to be conducted during the class, as each activity is designed to take up a significant portion of the available time.

Objectives

Duration: (5 - 10 minutes)

This stage of the lesson plan is essential to establish a solid theoretical understanding of the topic of enthalpy. By defining and explaining the main objectives, the teacher guides the students on what is expected for them to understand and be able to do by the end of the lesson. This helps focus the pre-class independent study and directs the discussions in class towards practical applications and clarification of doubts.

Main Objectives:

1. Empower students to understand the concept of enthalpy and how to calculate its values, considering heat exchange at constant pressure.

2. Differentiate and identify the main types of enthalpy (enthalpy of formation, enthalpy of reaction, and enthalpy of combustion) and their characteristic values.

3. Develop the ability to determine whether a reaction is exothermic or endothermic using the concepts of enthalpy.

Side Objectives:

1. Encourage the active participation of students in discussing and solving practical problems in groups, promoting the development of teamwork and communication skills.

Introduction

Duration: (20 - 25 minutes)

The introduction serves to engage students with the content they studied previously, using problem situations that stimulate the direct application of enthalpy concepts. Additionally, the contextualization aims to show the practical and theoretical relevance of the study of enthalpy by connecting it with real situations and curiosities that spark the interest and curiosity of students, facilitating knowledge internalization.

Problem-Based Situations

1. Consider the combustion of 1 mole of carbon (C) in the presence of oxygen (O₂) to form carbon dioxide (CO₂) at constant pressure. If the enthalpy of formation of CO₂ is -393.5 kJ/mol and that of C is 0, what is the enthalpy change for this reaction?

2. A student attempted to prepare water from its elements, hydrogen and oxygen, both gases under standard temperature and pressure (STP). Knowing that the enthalpy of formation of H₂O is -285.8 kJ/mol and that the enthalpy of formation of H₂ and O₂ is 0, ask to calculate the enthalpy of the reaction.

Contextualization

Enthalpy is a thermodynamic property that plays a crucial role in all chemical processes, from the combustion of fuels to the synthesis of substances in laboratories. For example, understanding the enthalpy of combustion of a fuel can help predict its energy efficiency and environmental impacts. Additionally, the enthalpy of formation is essential for calculating the energy involved in producing substances from their elements, which is fundamental for the development of new materials and industrial processes.

Development

Duration: (65 - 75 minutes)

The Development stage is designed for students to practically and interactively apply the concepts of enthalpy they studied previously. Through playful and contextualized activities, students can visualize and manipulate chemical reactions, facilitating understanding and retention of knowledge. This stage also aims to strengthen teamwork skills and the ability to solve complex problems, essential for the academic and professional development of students.

Activity Suggestions

It is recommended to carry out only one of the suggested activities

Activity 1 - Kitchen Adventure: Calculating the Enthalpy of Dishes

> Duration: (60 - 70 minutes)

- Objective: Apply the concept of formation enthalpy in everyday contexts and develop calculation and chemical reaction analysis skills.

- Description: In this activity, students become laboratory chefs and must calculate the enthalpy involved in preparing three dishes: a carrot cake, an omelet, and an orange juice. Each group receives a detailed recipe and the enthalpies of formation of the main ingredients, and must calculate the enthalpy change for each dish.

- Instructions:

• Divide the class into groups of up to 5 students.

• Distribute the recipes and the enthalpies of formation of the ingredients.

• Each group must calculate the formation enthalpy of each dish by summing the enthalpies of the ingredients used in the recipe.

• Present the calculations and discuss the enthalpy changes observed for the different dishes.

• Prepare a brief justification for classifying the reactions as endothermic or exothermic.

Activity 2 - Fuel Challenge: Investigating the Enthalpy of Combustion

> Duration: (60 - 70 minutes)

- Objective: Understand and experimentally calculate the enthalpy of combustion of different materials, applying concepts of calorimetry and enthalpy.

- Description: Students, organized in groups, receive samples of different fuels (such as alcohol, gasoline, and coal) and must experimentally measure the enthalpy of combustion for each one. They use a simple calorimeter and perform controlled burning of the fuels, measuring the temperature variation of the surrounding water to calculate the enthalpy.

- Instructions:

• Organize the room into workstations, each with a different fuel and a calorimeter.

• Instruct students on the safe use of the calorimeter and the handling of fuels.

• Record the initial mass of the fuel and water, and the initial temperature of the water.

• Carry out the burning of the fuel, observing and recording the temperature variation of the water.

• Calculate the enthalpy of combustion using the equation q = mcΔT and the collected data.

Activity 3 - Chemical Cinema: Analysis of Endothermic and Exothermic Reactions

> Duration: (60 - 70 minutes)

- Objective: Develop observation and critical analysis skills, as well as apply the concept of enthalpy in practice.

- Description: Students watch videos of chemical reactions, previously selected and prepared by the teacher, and must identify whether the reactions are endothermic or exothermic based on the observed changes (release or absorption of heat). Subsequently, they perform calculations to determine the enthalpy of the observed reactions.

- Instructions:

• Prepare a projection environment for the videos.

• Distribute observation sheets for students to record their analyses.

• Watch the reaction videos and discuss the observations in groups.

• Calculate the enthalpy of the observed reactions using the data provided by the videos.

• Present the findings and justify the classifications of the reactions.

Feedback

Duration: (15 - 20 minutes)

The purpose of this stage is to consolidate learning, allowing students to articulate and share the knowledge acquired through practical activities. This discussion helps clarify any remaining confusion, reinforces the concepts of enthalpy, and promotes a deeper understanding of the topic. Moreover, by listening to the experiences and conclusions of peers, students can gain new perspectives and insights, enriching their learning.

Group Discussion

After completing the activities, gather all students for a group discussion. Start the discussion with a brief introduction on the importance of sharing discoveries and learnings. Then, ask each group to present a summary of what they did and the conclusions they reached. Encourage students to discuss the differences and similarities between the results of the various groups and how these variations can be explained by the concepts of enthalpy studied. Use this moment to reinforce key concepts and clarify any possible doubts.

Key Questions

1. What were the main difficulties encountered when calculating enthalpy in the different activities?

2. How did you use the concepts of enthalpy to differentiate between endothermic and exothermic reactions?

3. How did the practical activities help solidify the theoretical understanding of enthalpy?

Conclusion

Duration: (10 - 15 minutes)

The conclusion stage serves to reinforce and consolidate the acquired knowledge, ensuring that students have understood the fundamental concepts of enthalpy and its practical applications. Additionally, by linking theory to practice and discussing the relevance of the topic, it increases the perception of the utility and importance of the subject, motivating students to continue exploring and applying this knowledge.

Summary

In conclusion, recap the main points addressed in the lesson, such as the definition of enthalpy, the types of enthalpy (enthalpy of formation, enthalpy of reaction, and enthalpy of combustion), and the calculations involved. It is crucial to remember the differences between exothermic and endothermic reactions and how they manifest in terms of enthalpy.

Theory Connection

Explain how practical activities, such as 'Kitchen Adventure' and 'Fuel Challenge', helped connect theory to practice. Show how the calculations performed in the laboratory reflect theoretical concepts, facilitating understanding and demonstrating the application of the studied concepts in real-life and everyday situations.

Closing

Finally, highlight the importance of studying enthalpy, not only in chemistry as an academic discipline but also in its practical application in industrial, environmental, and everyday processes. Emphasize how understanding enthalpy allows predicting and controlling chemical reactions, influencing the development of new materials and more efficient methods.