Objectives (5 - 10 minutes)

1. Understand the concept of equilibrium constant and its importance in chemical reactions.
2. Learn how to calculate the equilibrium constant from the concentrations of reactants and products.
3. Grasp how changes in concentrations affect the equilibrium constant and the direction of the reaction.

Secondary Objectives:

• Foster a deeper interest and understanding of chemistry and its practical applications.
• Develop problem-solving and critical thinking skills through hands-on activities.

Introduction (10 - 15 minutes)

1. The teacher begins by reminding students of the concepts of chemical reactions, specifically dynamic equilibrium, they've previously learned. This includes the idea that in a closed system, a chemical reaction can reach a point where the rate of the forward reaction equals the rate of the backward reaction, creating a state of balance.

2. The teacher then presents two problem situations:

   • The first situation involves a closed container with a reaction that produces a colored product. The teacher asks, "What would happen if we added more of one reactant? Would the color change? If so, how?".
   • The second situation involves a reaction used in industry, such as the Haber process for ammonia production. The teacher asks, "How can we manipulate the concentrations of the reactants to maximize the production of ammonia?".

3. The teacher then contextualizes the importance of the equilibrium constant in real-world applications. For example, in the pharmaceutical industry, understanding equilibrium constants is crucial to predict how drugs will interact in the body. In environmental science, it helps predict how pollutants will behave in the atmosphere and bodies of water.

4. The topic of equilibrium constant and concentrations is introduced with two intriguing points:

   • The teacher tells the story of Fritz Haber, who won the Nobel Prize in Chemistry for developing a method to synthesize ammonia from nitrogen and hydrogen, a process highly dependent on understanding equilibrium constants. This method significantly influenced agricultural and military developments in the 20th century.
   • A fun fact is shared about how scuba divers need to understand partial pressure (related to equilibrium constants) to avoid decompression sickness ("the bends"), illustrating how this seemingly abstract concept has very concrete implications.

5. Finally, the teacher explains that they will be exploring the concept of equilibrium constant and how it relates to the concentrations of reactants and products in a chemical reaction. They will also conduct hands-on experiments to see these concepts in action.

Development (20 - 25 minutes)

Activity 1: The Colour Changing Equilibrium

Objective: This experiment aims to give a vivid illustration of the concept of equilibrium and the impact of concentration changes.

1. Students are divided into groups of four and each group is provided with a bottle, vinegar (acetic acid), food coloring (red), and baking soda (sodium bicarbonate).
2. Each group is instructed to put a small amount of baking soda in their bottle and add a couple of drops of food coloring.
3. They are then told to add vinegar slowly and observe the vigorous reaction (bubbles and fizz) that changes the color of the solution to a vibrant red.
4. After the reaction subsides, they notice that the color starts to change back. This illustrates that the reaction is reversible and is now in equilibrium.
5. The group is then asked to add more baking soda, observing the change in color and noting whether the system eventually reverts to equilibrium.
6. To conclude, the teacher facilitates a discussion about how the change in concentration of reactants (the addition of more baking soda) affected the product concentration and hence the equilibrium of the system.

Activity 2: The Debate: The Haber Process and its Impact on Society

Objective: This debate aims to help students understand how the principle of equilibrium is applied in an industrial setting, as well as to ponder the ethical implications of scientific advancements.

1. The class is divided into two groups, with one arguing for the positive impacts of the Haber Process (increased food production etc.) and the other arguing for the negative consequences (Haber's role in the invention of poisonous gases used in WWI etc.).
2. Each group is given 10 minutes to prepare their arguments. They will be encouraged to connect the concept of equilibrium, and the understanding of how changing concentrations can shift the equilibrium, to their arguments whenever relevant.
3. After preparation, each group has a 5-minute slot to present their case to the class, followed by a collective discussion.
4. Students are then asked to write a short reflection on what they have learned about the intertwining of science (equilibrium in this case), industry, and society.

Activity 3: The Equilibrium Constant Puzzle

Objective: This paper-based activity is meant to encourage peer learning and consolidate understanding of the calculation of the equilibrium constant, K.

1. The teacher prepares worksheets with a chemical reaction at equilibrium and the concentrations of the reactants and products. Examples could include the reaction between nitrogen and hydrogen to produce ammonia (utilizing the Haber process taught earlier) or the reaction of carbon monoxide and chlorine gas to produce phosgene.
2. The students are divided into pairs and each pair is assigned a different set of reactants and products with given concentrations. However, the concentration of one product or reactant is missing.
3. Each pair is tasked with calculating the equilibrium constant using the given concentrations and then work out the missing concentration using their calculated K value.
4. Pairs take turns presenting their problem and solution to the class, explaining their thought process and calculations.
5. To conclude, the teacher should offer feedback and corrections as needed and help students understand any common misconceptions.

Feedback (5 - 10 minutes)

1. The teacher initiates a discussion with the whole class, asking each group to share their observations and conclusions from the hands-on activities. Some guiding questions can be:

   • What happened when you added more baking soda in Activity 1? How does this relate to the concept of equilibrium?
   • How did you apply the concept of equilibrium in the debate about the Haber Process in Activity 2?
   • What steps did you take to calculate the missing concentration in Activity 3? How does the equilibrium constant help us in this calculation?

2. The teacher then prompts students to reflect on the connection between the activities and the theory of equilibrium constant and concentrations. The teacher may ask the following questions:

   • How did the activities help you understand the concept of equilibrium constant and its relationship with the concentrations of reactants and products?
   • How are these concepts applied in real-world situations like the Haber Process or scuba diving?

3. The teacher encourages students to take a few minutes to reflect individually on the lesson. The teacher provides guiding questions for this reflection:

   • What was the most important concept you learned today?
   • What questions do you still have about equilibrium constant and concentrations?
   • How can you apply what you learned today in real-life situations?

4. After the reflections, the teacher opens up the floor for students to share their thoughts and ask any lingering questions. The teacher should make sure that all students understand the basic concepts and are comfortable with the calculations related to the equilibrium constant.

5. To conclude the feedback session, the teacher summarizes the main points of the lesson, reiterates the importance of understanding equilibrium constants, and highlights how this understanding can be applied in different fields like industry, medicine, and environmental science.

6. The teacher then assigns homework to reinforce the day's learning. The homework could consist of additional problems involving calculation of equilibrium constants and concentrations. The teacher also encourages students to research more about how the concept of equilibrium constant is applied in industrial processes and everyday life.

7. Finally, the teacher thanks the students for their active participation and encourages them to continue exploring and asking questions about the fascinating world of chemistry.

Conclusion (5 - 10 minutes)

1. The teacher begins by summarizing the main contents of the lesson. They reiterate the concept of equilibrium constant and its relationship with the concentrations of reactants and products in a chemical reaction. The teacher reminds students that the equilibrium constant is a measure of the ratio of product concentrations to reactant concentrations at equilibrium.

2. The teacher then explains how the lesson connected theory, practice, and applications. The hands-on experiment with vinegar and baking soda illustrated the shifts in equilibrium in response to changes in concentration. The debate about the Haber Process contextualized the importance of understanding equilibrium in industrial settings, and the equilibrium constant puzzle allowed students to apply their theoretical understanding in practical calculations.

3. The teacher suggests additional materials for students to further their understanding of equilibrium constant and concentrations. These could include online resources, textbooks, or science experiments that can be done at home. The teacher could also recommend documentaries or articles about Fritz Haber and the Haber Process, or about other industrial processes that rely on understanding chemical equilibrium.

4. The teacher then emphasizes the importance of the lesson's topic for everyday life. They explain that understanding equilibrium constants and concentrations is not just for passing exams or getting good grades in chemistry class; it has real-world applications. For example, in the pharmaceutical industry, knowing how to manipulate equilibrium can help create more effective drugs. In environmental science, it can help predict the behavior of pollutants. Even in everyday situations like cooking or cleaning, understanding how chemicals react and reach equilibrium can be very useful.

5. Finally, the teacher encourages students to continue exploring the topic and to always be curious about the world around them. They remind students that chemistry is not just a subject in school, but a tool for understanding and interacting with the world. The teacher concludes the lesson by thanking the students for their active participation and enthusiasm.