Lesson Plan | Technical Methodology | Thermochemistry: Hess's Law

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to ensure that students understand the objectives of the lesson and the relevance of learning Hess's Law to calculate enthalpies of chemical reactions. Developing practical skills in this context is essential to prepare students for real-world challenges in the job market, where thermochemistry is applied in various industries such as pharmaceuticals, petrochemicals, and materials. Furthermore, this theoretical and practical foundation is fundamental for students wishing to pursue careers in scientific and engineering fields.

Main Objectives

1. Explain Hess's Law and its importance in Thermochemistry.

2. Demonstrate how to use Hess's Law to calculate the enthalpy of a chemical reaction.

Side Objectives

1. Reinforce the concept of enthalpy of formation.
2. Introduce practical examples of the application of Hess's Law in the job market.

Introduction

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to ensure that students understand the objectives of the lesson and the relevance of learning Hess's Law to calculate enthalpies of chemical reactions. Developing practical skills in this context is essential to prepare students for real-world challenges in the job market, where thermochemistry is applied in various industries such as pharmaceuticals, petrochemicals, and materials. Furthermore, this theoretical and practical foundation is fundamental for students wishing to pursue careers in scientific and engineering fields.

Contextualization

Hess's Law is one of the pillars of Thermochemistry, a branch of Chemistry that studies the energy changes accompanying chemical reactions. Imagine being able to predict the amount of heat released or absorbed in a reaction, something crucial in industrial processes such as the production of food, fuels, and medicines. This prediction is possible thanks to Hess's Law, which allows us to calculate the enthalpy of a complex reaction from simpler reactions whose enthalpies are known.

Curiosities and Market Connection

💡 Curiosity: The principle behind Hess's Law was discovered by Swiss chemist Germain Henri Hess in 1840, and has since been a vital tool for engineers and scientists. 🏭 Market Application: In the petrochemical industry, for example, Hess's Law is used to optimize oil refining processes, ensuring energy efficiency and saving resources. In pharmaceuticals, it aids in the synthesis of compounds that require precise control of temperature and energy to ensure efficacy and safety.

Initial Activity

🎥 Initial Activity: Show a short video (3-5 minutes) demonstrating the application of Hess's Law in an industrial process, such as the synthesis of a medication. After the video, ask the following provoking question: 'How do you think Hess's Law can influence energy efficiency in chemical industries?' Have students discuss in pairs and share their ideas with the class.

Development

Duration: (60 - 70 minutes)

The purpose of this stage of the lesson plan is to provide a practical and applied understanding of Hess's Law, allowing students to develop technical and analytical skills relevant to the job market. By engaging students in simulation and problem-solving activities, they have the opportunity to apply theoretical concepts in real contexts, fostering meaningful learning and preparation for future challenges.

Covered Topics

1. Hess's Law: Definition and Importance
2. Enthalpy of Formation
3. How to Use Hess's Law to Calculate Enthalpies of Reactions
4. Practical Examples of Hess's Law Application in the Job Market

Reflections on the Theme

Guide students to reflect on how Hess's Law can impact industrial and scientific processes. Ask: 'How can the ability to predict the enthalpy of a reaction influence the efficiency and safety of industrial processes?'. Encourage them to think of specific examples, such as the production of medicines or oil refining, and to discuss how thermochemical knowledge can be a competitive differential in the job market.

Mini Challenge

Maker Challenge: Building a Virtual Chemical Reaction

Students will use a chemical simulation software (like PhET Interactive Simulations or another available tool) to model a series of chemical reactions and apply Hess's Law to calculate the enthalpy of the overall reaction.

Instructions

1. Divide the class into groups of 3-4 students.
2. Provide each group access to the chemical simulation software.
3. Ask the groups to choose a complex chemical reaction they wish to simulate.
4. Guide them to identify intermediate reactions whose enthalpies are known and to use Hess's Law to calculate the enthalpy of the overall reaction.
5. Encourage students to document each step of the process, including the chemical equations and enthalpy calculations.
6. After the simulation, each group should prepare a brief presentation (3-5 minutes) explaining the process they followed and the results obtained.

Objective: Apply Hess's Law in a practical and technological context, developing modeling and simulation skills that are highly valued in the job market.

Duration: (35 - 45 minutes)

Evaluation Exercises

1. Calculate the enthalpy of the overall reaction using the following intermediate reactions and their respective enthalpies:
2. Reaction 1: A + B → C, ΔH = -100 kJ/mol
3. Reaction 2: C → D + E, ΔH = +50 kJ/mol
4. Reaction 3: E + F → G, ΔH = -30 kJ/mol
5. Determine the enthalpy of the reaction: A + B + F → D + G
6. Explain how Hess's Law can be used to optimize a specific industrial production process (choose an example from an industry, such as pharmaceuticals or petrochemicals).

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to consolidate the knowledge acquired by students, fostering a critical reflection on the practical application of Hess's Law. By summarizing the content and encouraging discussion, it aims to ensure that students understand the relevance of the topic for the job market and are prepared to use the skills developed in real contexts.

Discussion

Encourage a discussion with students about how Hess's Law can be applied in different industrial and scientific contexts. Invite them to share insights on the maker challenge and the fixation exercises, highlighting difficulties encountered and creative solutions developed. Ask: 'What were the main learnings from applying Hess's Law in the simulation? How can this tool be useful in your future careers?'

Summary

Summarize the main content presented, emphasizing the definition of Hess's Law, the importance of the enthalpy of formation, and the practical application of Hess's Law in calculating the enthalpy of reactions. Reinforce the connection between learned theory and its applications in the job market, especially in pharmaceuticals and petrochemicals.

Closing

Explain how the lesson connected theory, practice, and applications of Hess's Law. Highlight the importance of thermochemical learning for the efficiency and safety of industrial processes. Conclude by emphasizing that the ability to calculate the enthalpy of chemical reactions is a valuable and applicable skill in various professional areas, from academic research to cutting-edge industry.