Objectives (5 - 7 minutes)

1. Understand the structure of aldehyde: The teacher should introduce the concept of aldehyde, explaining its general structure and distinctive characteristics. The presence of the aldehyde functional group (C=O) in its structure and how it affects its chemical properties should be highlighted.

2. Identify aldehydes in complex structures: Students should be able to identify the aldehyde functional group in a complex chemical structure. For this, they should learn to recognize the presence of the aldehyde carbon (C=O) and the atoms attached to it.

3. Understand the properties and uses of aldehydes: Students should be able to associate the presence of aldehydes with specific chemical properties, such as the ability to reduce metal ions. Additionally, they should learn about the common uses of aldehydes in industry and daily life, such as food preservatives and raw materials for the production of plastics and resins.

Secondary objectives:

• Develop problem-solving skills: Through the practice of identifying aldehydes in complex structures, students will be challenged to apply the knowledge acquired to solve problems.

• Promote autonomous learning: Through the use of digital resources and practical activities, students will be encouraged to learn autonomously, researching additional information and applying it to the concepts learned.

Introduction (10 - 15 minutes)

1. Review of Previous Content: The teacher begins the lesson by recalling the concepts of organic functions already studied, such as hydrocarbons, alcohols, and ketones. This review is essential for students to establish relationships between different functional groups and better understand the properties of aldehyde.

2. Problem Situations:

   • Situation 1: The teacher can present an example of a chemical reaction where an aldehyde is formed, such as the oxidation of a primary alcohol. Students will be challenged to identify the formed aldehyde and explain why this reaction did not result in the formation of a carboxylic acid or a ketone.

   • Situation 2: The teacher can present an image of a cut fruit or vegetable that has started to darken. Students will be challenged to explain why this occurs and identify the substance responsible for this process, which is an aldehyde, melanin.

3. Contextualization: The teacher should emphasize the importance of aldehydes in various industries and our daily lives. It can be mentioned that aldehydes are used as food preservatives, in perfumes and fragrances, and as raw materials for the production of plastics and resins. Additionally, it can be mentioned that the ability of aldehydes to react with metal ions is the basis of many chemical tests, such as the Fehling test for the presence of reducing sugars.

4. Gaining Students' Attention:

   • Curiosity 1: The teacher can share the curiosity that the first aldehyde to be synthesized by man was formaldehyde, in 1859, by August Wilhelm von Hofmann. He did this by oxidizing methanol, the simplest alcohol.

   • Curiosity 2: The teacher can talk about how aldehydes can be found in nature, such as cinnamaldehyde, responsible for the characteristic aroma of cinnamon.

   • Relation to Daily Life: The teacher can highlight that, in addition to their industrial applications, aldehydes also play an important role in biology. For example, formaldehyde is used to preserve tissues in laboratories, and melanin, an aldehyde, is responsible for the color of skin, hair, and eyes in humans and animals.

Development (20 - 25 minutes)

1. Theory - Aldehydes and their Properties (10 - 12 minutes)

   • Definition and Structure of Aldehyde: The teacher should start by explaining that aldehydes are organic compounds that have the aldehyde functional group (C=O) attached to at least one hydrogen. The general structure of an aldehyde is R-CHO, where R can represent a hydrogen or an alkyl group. It should be emphasized that the carbon of the aldehyde group is always the first carbon of the chain.

   • Nomenclature of Aldehyde: The teacher should explain that, in IUPAC nomenclature, aldehydes are named by replacing the ending "o" of the corresponding hydrocarbon name with "al". It should be noted that if the main chain has more than three carbons, the carbon of the aldehyde group is numbered as C1. Example: methanal (formaldehyde), ethanal (acetaldehyde).

   • Physical Properties of Aldehydes: The teacher should discuss that open-chain aldehydes are volatile liquids with characteristic odors. It should be explained that aldehydes have lower boiling points than alcohols of similar molecular mass due to the absence of intermolecular hydrogen bonds in aldehydes. Additionally, it should be mentioned that aldehydes are soluble in water at low molecular masses, but solubility decreases with increasing molecular mass.

   • Reactivity of Aldehydes: The teacher should explain that aldehydes are easily oxidized to carboxylic acids, and this characteristic is used in Fehling and Tollens tests for aldehydes. Additionally, aldehydes can be reduced to primary alcohols, and this reaction is used in the production of alcohols in the laboratory. Finally, it should be mentioned that aldehydes are more reactive than ketones due to the presence of a hydrogen attached to the carbon of the aldehyde group, which facilitates oxidation and reduction.

2. Theory - Identification of Aldehydes (5 - 7 minutes)

   • Identification of Aldehydes in Complex Structures: The teacher should explain that to identify an aldehyde in a complex structure, students should look for the aldehyde functional group (C=O) and the atoms attached to it. It should be noted that if an aldehyde is in a main chain, the carbon of the aldehyde group is numbered as C1.

   • Exercises for Identifying Aldehydes: The teacher should present some examples of complex chemical structures and challenge students to identify the aldehydes present in them. Students should be encouraged to discuss their answers and justify them based on what they have learned about the structure and properties of aldehydes.

3. Application - Uses of Aldehydes (5 - 6 minutes)

   • Uses in Industry and Daily Life: The teacher should present some examples of the uses of aldehydes in industry and daily life. It can be mentioned that aldehydes are used as food preservatives, in perfumes and fragrances, and as raw materials for the production of plastics and resins. The teacher should briefly explain how the chemical properties of aldehydes are useful in each of these applications.

4. Practical Activity - Modeling Aldehydes (5 - 7 minutes)

   • Modeling Aldehydes with Clay: The teacher should provide students with modeling clay of different colors. Students will be challenged to model the structures of specific aldehydes, such as methanal (formaldehyde) and ethanal (acetaldehyde), using the clay color to represent different atoms. This activity will help students visualize the structure of aldehydes and better understand the relationship between the structure and properties of organic compounds.

   • Discussion about the Modeled Structures: After the activity, students will be encouraged to discuss their modeled structures and explain how the structure of the aldehyde influences its chemical properties and uses. The teacher should provide guidance and clarify any doubts students may have.

Note: The estimated times for each section are just a reference. The teacher can adjust the duration of each section according to the needs and pace of the class.

Return (8 - 10 minutes)

1. Group Discussion (3 - 4 minutes)

   • The teacher should promote a group discussion about the solutions or conclusions found by each team. Each group will have up to 3 minutes to present their modeled structures and explain the relationship between the structure of the aldehyde, its chemical properties, and uses.

   • Other students will be encouraged to ask questions and comment on their colleagues' presentations. The teacher should monitor the discussion, ensuring that all students have the opportunity to participate.

2. Connection with Theory (2 - 3 minutes)

   • After the group discussion, the teacher should make a brief review of the theoretical concepts discussed in the lesson, relating them to the solutions or conclusions presented by the students. For example, the teacher can comment on how the presence of the aldehyde functional group (C=O) influences the chemical properties of aldehydes and how this was reflected in the structures modeled by the students.

3. Individual Reflection (2 - 3 minutes)

   • The teacher should propose that students individually reflect on what they learned in the lesson. For this, the teacher can ask the following questions:

     1. What was the most important concept you learned today?
     2. What questions remain unanswered?

   • Students will have one minute to think about their answers. Then, the teacher can ask some students to share their reflections with the class. The teacher should encourage students to express their doubts and ask questions, ensuring that everyone feels comfortable participating.

4. Feedback and Closure (1 minute)

   • To close the lesson, the teacher can ask for quick feedback from the students about the lesson. The teacher can ask what the students liked most about the lesson and what they found most challenging. Student feedback can be useful for the teacher to assess the effectiveness of the lesson and make adjustments for future lessons.

   • The teacher should thank everyone for their participation and effort, reinforce the importance of continuous study, and encourage students to bring their questions to the next lesson.

Note: The estimated time for each section is just a reference. The teacher can adjust the duration of each section according to the needs and pace of the class. Additionally, the teacher can adapt the reflection questions according to the level of understanding of the class and the learning objectives of the lesson.

Conclusion (5 - 7 minutes)

1. Summary of Content (2 - 3 minutes)

   • The teacher should summarize the main points covered during the lesson. The definition of aldehyde, its structure, nomenclature, and physical and chemical properties should be reinforced. Additionally, the uses of aldehydes in industry and daily life should be recapped.

   • The teacher can use interactivity with the students and recall the structures modeled during the practical activity, highlighting again the importance of the aldehyde structure for its properties and uses.

2. Connection between Theory, Practice, and Applications (1 - 2 minutes)

   • The teacher should explain how the lesson connected theory, practice, and applications. It should be highlighted how the theory about the structure and properties of aldehydes was applied in the practical modeling activity, and how this understanding is relevant to understanding the uses of aldehydes in industry and daily life.

   • The teacher can also reinforce the importance of developing problem-solving skills and critical thinking, which were promoted during the lesson.

3. Supplementary Materials (1 minute)

   • The teacher should suggest supplementary materials for students who wish to deepen their knowledge about aldehydes. This can include additional readings, educational videos, interactive chemistry websites, and reinforcement exercises.

   • The teacher can also encourage students to research more about the uses of aldehydes in industry and daily life and bring their findings to the next lesson.

4. Importance of Aldehydes (1 minute)

   • To close the lesson, the teacher should emphasize the importance of aldehydes for our daily lives and industry. It should be highlighted that, in addition to their industrial applications, aldehydes also play an important role in biology, such as in the formation of melanin, and in analytical chemistry, such as in the Fehling test for the presence of reducing sugars.

   • The teacher should encourage students to be aware of the presence and uses of aldehydes in their environment and to understand how the chemistry of aldehydes affects their properties and uses.

Note: The estimated time for each section is just a reference. The teacher can adjust the duration of each section according to the needs and pace of the class. Additionally, the teacher can adapt the suggestions for supplementary materials according to the level of understanding and interests of the class.