Lesson plan of Concentration Units: % Mass, Volume and Other Units

Objectives (5 - 7 minutes)

1. Understand concentration units: Students should be able to understand the concept of concentration units, including how they are used to express the amount of a substance in a solution. They should be able to differentiate between different types of concentration units, such as percent by mass, percent by volume, and molarity.

2. Perform concentration unit calculations: Students should be able to perform simple calculations to determine the amount of a substance in a solution, given the concentration and volume. They should be able to convert between different types of concentration units.

3. Apply the concept: Students should be able to apply their understanding of concentration units to solve practical problems. This includes the ability to determine the amount of a substance needed to prepare a solution of a specific concentration and the ability to determine the concentration of a solution given the amount of solute and solvent.

   • Secondary Objective: Develop critical thinking and problem-solving skills, which are transferable skills that students can apply to other areas of chemistry and life.

During the Getting Started portion of class, the instructor should clearly articulate these Objectives, ensuring that students understand what will be expected of them by the end of class. Students should be encouraged to ask questions and clarify any uncertainties they may have regarding these Objectives.

Getting Started (10 - 15 minutes)

1. Review of Prior Knowledge: The instructor should begin class by briefly reviewing the concepts of solution, solute, and solvent, as well as different ways of expressing the concentration of a solution, such as molarity and normality. This serves to reinforce students' prior knowledge and prepare them for the new content. (3 - 5 min)

2. Problem Scenarios: The instructor should then present two problem scenarios that involve the use of concentration units.

   • Scenario 1: Imagine you need to prepare a 20% sulfuric acid solution. You have a 100-mL bottle of 40% sulfuric acid. How much of this acid do you need to add to an empty 100-mL flask to obtain the desired solution?

   • Scenario 2: Suppose you need to prepare a 2 M sodium chloride solution. You have a 250-mL bottle of 4 M sodium chloride. How much of this chloride do you need to add to an empty 250-mL flask to obtain the desired solution?

   The instructor should ask students to think about how they would solve these problems and to write down any questions or difficulties they may have. (5 - 7 min)

3. Contextualization: The instructor should then contextualize the importance of concentration units, explaining that they are widely used in many fields, including chemistry, biology, medicine, industry, and agriculture. For example, in medicine, the concentration of a drug in a solution can affect its effectiveness and safety. Similarly, in agriculture, the concentration of a fertilizer in a solution can affect plant growth. (2 - 3 min)

4. Attention Grabber: To conclude the Getting Started and grab students' attention, the instructor could share two fun facts about concentration units:

   • Fun Fact 1: The concept of molarity was introduced by French chemist François-Marie Raoult in the late 19th century. He proposed that the vapor pressure of a solution is proportional to the number of solute particles in the solution, which is the basis of the modern definition of molarity.

   • Fun Fact 2: Did you know that molarity is used in a variety of everyday applications? For example, in the preparation of sports drinks, molarity is used to determine the amount of electrolytes (such as sodium and potassium) that should be added to the water. (1 - 2 min)

Development (20 - 25 minutes)

1. Problem-Solving Activity: The instructor should divide the class into groups of 4-5 students and provide each group with the two problem scenarios presented in the Getting Started. Students should work together to solve these problems, applying the concepts of concentration units that they have learned. The instructor should circulate the room, providing guidance and clarifying questions as needed. (10 - 12 min)

   • Hint: To facilitate solving the problems, the instructor can ask students to outline a plan, identifying the information given, what they are trying to find, and what formulas or methods they will need to use. This can help them organize their thoughts and make the problem more manageable.

   • Hint: The instructor can also encourage students to work efficiently, by dividing tasks among group members and checking their answers to make sure they make sense.

2. Hands-on Activity: After the problems have been solved, the instructor should provide each group with a set of laboratory materials, including different substances and measuring containers. The students should then be challenged to prepare a solution of a specific concentration (e.g., 5% acetic acid) by carefully measuring the amount of solute and solvent that they use and converting this information to the desired concentration unit. (8 - 10 min)

   • Hint: The instructor should ensure that the laboratory materials are safe and appropriate for student use. Furthermore, it is important for the instructor to provide guidance and supervision during this activity to ensure that students are working safely and efficiently.

   • Hint: To make the activity more engaging, the instructor can make it competitive by challenging each group to prepare the solution with the most accurate concentration.

3. Discussion and Reflection: After the activities have been completed, the instructor should lead a class discussion to review the problem solutions and the students' experiences in the hands-on activity. The instructor should reinforce the key concepts and clarify any questions that may still exist. Additionally, the instructor should ask students to reflect on what they have learned and how they can apply this knowledge in real-world situations. (2 - 3 min)

   • Hint: The instructor can ask open-ended questions to stimulate student reflection, such as "How did you use concentration units to solve the problems?" and "How did the hands-on activity help solidify your understanding of this concept?".

   • Hint: The instructor can also ask students to identify any areas of the topic that they do not yet fully understand, so that these can be addressed in future classes.

Turning (10 - 15 minutes)

1. Group Discussion: The instructor should facilitate a group discussion with the entire class. Each group should share their solutions to the problem scenarios presented at the beginning of class, as well as their experiences and challenges in the hands-on activity. The instructor should encourage students to ask each other questions and provide constructive feedback. This discussion allows students to learn from each other, reinforcing their understanding of the topic. (5 - 7 min)

   • Hint: To facilitate the discussion, the instructor can prepare some guiding questions, such as "How did your group approach solving the problems?" and "What were the major challenges your group faced in the hands-on activity?".

2. Theory Connection: Following the discussion, the instructor should connect the activities that were done to the theory presented at the beginning of class. The instructor should highlight how solving the problems and doing the hands-on activity illustrated the concepts of concentration units and how they are used in practice. This helps students see the relevance of what they have learned and make connections to other situations. (2 - 3 min)

   • Hint: The instructor can use examples from the group discussion to illustrate the points of connection, highlighting how the concepts were applied to solve the problems and do the hands-on activity.

3. Individual Reflection: Finally, the instructor should ask students to reflect individually on what they have learned in class. The instructor could ask questions such as:

   1. "What was the most important concept you learned today?"
   2. "What questions do you still have?"

   Students should be encouraged to write down their answers, as this can help them solidify their learning and identify any gaps in their understanding that need to be addressed. (3 - 5 min)

   • Hint: The instructor can ask students to share their answers with the class, if they are comfortable doing so, to promote discussion and reflection among students.

   • Hint: The instructor should remind students that they can always ask questions or seek clarification in future classes, and that fully understanding a topic can take time and practice.

Closing (5 - 7 minutes)

1. Content Summary: The instructor should begin the Closing by summarizing the major points that were covered. This includes the definition of concentration units, the differences between different types of concentration units (such as percent by mass, percent by volume, and molarity), and how to perform calculations using these units. The instructor should reinforce that molarity is one of the most important and widely used concentration units in chemistry. (2 - 3 min)

2. Connection between Theory, Practice, and Applications: The instructor should then highlight how the class connected the theory, practice, and applications of the concept of concentration units. They should explain that solving the problems and doing the hands-on activity allowed students to apply the theory to real-world situations, reinforcing their understanding and demonstrating the relevance of the topic. The instructor should reiterate that concentration units are widely used in many fields, including chemistry, biology, medicine, industry, and agriculture, and that therefore the ability to work with these units is a valuable and useful skill. (1 - 2 min)

3. Supplementary Materials: The instructor should then suggest some supplementary materials for students who want to further their understanding of the topic. This could include chemistry textbooks, reference websites, educational videos, and chemistry learning apps. The instructor should encourage students to explore these materials on their own time and at their own pace, and to bring any questions or areas of difficulty to future classes for discussion. (1 min)

   • Hint: Some helpful resources for students might include the textbook "Chemistry: The Central Science" by Brown, LeMay, and Bursten, the reference website ChemLibreTexts, the YouTube channel CrashCourse Chemistry, and the chemistry learning app Khan Academy.

4. Importance of the Topic: Finally, the instructor should emphasize the real-world relevance of the topic to students' everyday lives. They should explain that while concentration units may seem abstract, they are used in many everyday situations, such as when preparing food and drinks, administering medications, and maintaining swimming pools. The instructor should stress that understanding and being able to work with concentration units can help students be more informed and effective in many aspects of their lives. (1 - 2 min)

   • Hint: The instructor could provide specific examples of how concentration units are used in different everyday situations, to make the topic more concrete and relatable to students. For example, they could explain how the concentration of an ingredient in a recipe affects the taste of the dish, or how the concentration of a medication in a solution can affect its effectiveness and safety.