Objectives (5 - 7 minutes)

1. Understanding Air Composition: The teacher should introduce the concept of air composition to the students, explaining that the air is composed of different gases, such as nitrogen, oxygen, carbon dioxide, and other elements in smaller quantities. Students should understand that the atmosphere is composed of different layers, each with its own gas composition.

2. Identification of Air Components: Students should be able to identify the main components of the air and their proportions. To do this, the teacher should provide information about the quantity of each gas in the atmosphere and its importance for life on Earth.

3. Relationship between Air Composition and Life on Earth: Students should understand the importance of air composition for life on Earth. The teacher should explain how the balance between different gases in the atmosphere is crucial for the survival of all living beings.

Secondary Objectives

• Understanding the Greenhouse Effect: After understanding the air composition, students should be able to comprehend the greenhouse effect concept, which is directly related to the presence of carbon dioxide in the atmosphere.
• Reflection on Air Pollution: Based on the acquired knowledge, students should be able to reflect on air pollution and its effects, considering the importance of the atmosphere and air composition for life on Earth.

Introduction (10 - 12 minutes)

1. Review of Previous Content: The teacher should start the lesson by reminding students about the importance of air for life on Earth. He can ask questions like 'What are the main functions of air for living beings?' or 'What would happen if we didn't have air around us?'. This review will prepare students for the new content to be presented. (2 - 3 minutes)

2. Problem Situation 1: Earth without Atmosphere: The teacher should propose a hypothetical situation to the students: 'If the Earth didn't have an atmosphere, how would life be here?'. Students should be encouraged to think about the importance of the atmosphere and air for life as we know it. (2 - 3 minutes)

3. Problem Situation 2: Alteration in Air Composition: Next, the teacher should present another situation: 'What if the air composition changed? If the amount of oxygen decreased, what would happen?'. This question will introduce students to the idea that air composition is fundamental for life on Earth. (2 - 3 minutes)

4. Contextualization of the Importance of Air: The teacher should then contextualize the importance of air, mentioning how air composition is crucial for the existence of different forms of life, including plants, animals, and humans. Additionally, it can be mentioned how air pollution affects human health and the environment. (2 - 3 minutes)

5. Introduction to the Topic with Curiosities: To capture students' attention, the teacher can share some curiosities about air composition. For example, he can mention that nitrogen is the most abundant gas in the atmosphere, representing about 78% of its composition, while oxygen is the second most common, at around 21%. Additionally, it can be mentioned that carbon dioxide, although a greenhouse gas, is essential for life on Earth, as it is used by plants during photosynthesis. (2 - 3 minutes)

Development (20 - 25 minutes)

1. Theory of Air Composition (7 - 10 minutes): The teacher should start this stage by explaining that the air we breathe is a mixture of invisible gases. He should introduce the main components of the air, which are: nitrogen (78%), oxygen (21%), carbon dioxide (0.04%), and traces of other gases, such as argon, neon, and helium.

   • The teacher should then explain the characteristics and importance of each of these gases. For example, nitrogen is an inert gas that helps maintain constant atmospheric pressure. Oxygen, in turn, is essential for aerobic respiration, which is the process by which living beings obtain energy.
   • Carbon dioxide, although a greenhouse gas, is crucial for life on Earth, as it is used by plants during photosynthesis. The teacher should explain that the presence of carbon dioxide in the atmosphere is balanced through the carbon cycle, a natural process that involves the absorption and release of carbon dioxide by different reservoirs, such as the ocean and the biosphere.

2. Activity 1: Air Composition in the Classroom (5 - 7 minutes): The teacher should then propose a practical activity for the students. He should provide each group of students with a transparent container and a small candle. Students should light the candle and place it in the container, then cover the container with a balloon and observe what happens.

   • The teacher should explain that the candle consumes the oxygen from the air to burn. When it is covered by the balloon, the burning of the candle produces carbon dioxide, which is a gas. Students should observe that the candle starts to extinguish because it is consuming the oxygen, and the flame goes out when all the oxygen is consumed.
   • The teacher should then ask students what they think would happen if the candle continued to burn in the sealed container. This leads to a discussion on how the alteration in air composition (decrease in oxygen and increase in carbon dioxide) can affect life.

3. Greenhouse Effect Theory (3 - 5 minutes): The teacher should then introduce the greenhouse effect theory. He should explain that the greenhouse effect is a natural phenomenon that keeps the Earth warm, allowing life as we know it.

   • The teacher should explain that the sunlight reaching the Earth is largely composed of shortwave radiation. Most of this radiation passes through the atmosphere and reaches the Earth's surface, which then emits longer wave radiation back into space.
   • However, some of these longwave infrared rays are captured by greenhouse gases in the atmosphere, such as carbon dioxide. This causes the Earth's temperature to rise, creating the greenhouse effect. The teacher should explain that the increase in concentrations of greenhouse gases, due to human activity, is causing accelerated global warming.

4. Activity 2: Greenhouse Effect in the Classroom (5 - 7 minutes): To help students visualize the greenhouse effect, the teacher should propose a second activity. He should provide each group of students with a second transparent container, a small candle, and a piece of transparent plastic.

   • Students should place the candle in the second container and cover it with the plastic. They should observe that as the candle burns, the temperature in the container increases, as the plastic prevents carbon dioxide from escaping.
   • The teacher should explain that this is an analogy of what is happening on the planet. The activity helps students understand how the increase in greenhouse gases, such as carbon dioxide, can lead to a temperature rise on Earth, causing climate changes.

5. Final Discussion (2 - 3 minutes): To conclude the Development of the lesson, the teacher should open up a space for discussion. Students should be encouraged to ask questions, share their observations, and reflect on the importance of air composition and the greenhouse effect for life on Earth. The teacher should encourage a respectful and open discussion, providing guidance and clarifications as needed.

Return (8 - 10 minutes)

1. Review of Key Concepts (3 - 4 minutes): The teacher should summarize the main points covered during the lesson, reiterating the importance of each air component (nitrogen, oxygen, carbon dioxide, and other gases) and their relevance to life on Earth. He should emphasize how the alteration in air composition can affect life and introduce climate changes. The teacher can do this through a visual scheme, highlighting the proportion of each gas in the atmosphere and its function.

2. Connection between Theory and Practice (2 - 3 minutes): The teacher should then explain how the practical activities carried out by students (observation of the candle in the covered container and analysis of the greenhouse effect with the plastic) connect with the theory. He should reiterate that these activities served to illustrate the impact of the alteration in air composition and the presence of greenhouse gases on global warming.

3. Reflection on Learning (2 - 3 minutes): The teacher should then suggest that students reflect individually on what they learned during the lesson. He can ask questions like:

   1. 'What was the most important concept you learned today?'
   2. 'What questions have not been answered in your mind yet?'
   3. 'How can you apply what you learned today in your daily life?' After individual reflection, the teacher can ask some students to share their answers with the class. This can help identify any gaps in students' understanding and provide valuable feedback to the teacher.

4. Feedback and Closure (1 - 2 minutes): Finally, the teacher should provide feedback on the lesson, praising the students' efforts and highlighting the strengths of the discussion. He should encourage students to continue exploring the topic, suggesting additional readings or complementary activities. The teacher should then conclude the lesson, reminding students about the next topic and providing any other relevant information.

Conclusion (5 - 7 minutes)

1. Summary and Recapitulation (2 - 3 minutes): The teacher should start the Conclusion of the lesson by recalling the key points covered. He should summarize the air composition, including the main gases present in the atmosphere (nitrogen, oxygen, carbon dioxide, and others), their proportions, and their functions. Additionally, he should recapitulate the greenhouse effect concept, the importance of the balance of gases in the atmosphere, and how the alteration in this balance can lead to climate changes.

2. Theory-Practice-Reality Connection (1 - 2 minutes): Next, the teacher should highlight how the lesson connected theory, practice, and reality. He should recall the practical activities carried out by students and how these activities illustrated the presented theoretical concepts. Additionally, he should emphasize the importance of air composition and the greenhouse effect for life on Earth, showing how these concepts apply in the real world.

3. Extra Materials (1 - 2 minutes): The teacher should then suggest extra materials for further exploration of the topic. This may include articles, documentaries, interactive websites, and educational games about air composition, the greenhouse effect, and climate changes. For example, the teacher can recommend reading articles on air pollution and its consequences, or watching documentaries that present the importance of taking care of our planet.

4. Importance of the Subject (1 - 2 minutes): Finally, the teacher should summarize the importance of the topic addressed for students' daily lives. He should emphasize that understanding air composition and the greenhouse effect is essential to comprehend current environmental issues and make informed decisions on how we can contribute to the conservation of the planet. The teacher can conclude the lesson by reinforcing the importance of each individual in caring for the air we breathe and our environment as a whole.