Lesson Plan | Traditional Methodology | Thermodynamics: Gas Pressure

Objectives

Duration: (10 - 15 minutes)

This stage of the lesson plan aims to introduce students to the concept of pressure, providing a solid foundation for them to understand and calculate the pressure of a gas in different contexts. Additionally, it aims to highlight the relevance of this concept in the study of Thermodynamics and its practical applications, preparing students for the content that will be detailed throughout the lesson.

Main Objectives

1. Understand that pressure is the normal force applied to a surface divided by the area.

2. Calculate the pressure of a gas in a container using the appropriate formula.

3. Recognize the importance of pressure in the study of Thermodynamics and its application in everyday situations.

Introduction

Duration: (10 - 15 minutes)

 Purpose: The purpose of this stage of the lesson plan is to contextualize and motivate students for the study of gas pressure, establishing a foundation of understanding about how pressure influences various natural and technological phenomena. This prepares students for a deeper and applied understanding of the concept throughout the lesson.

Context

️ Context: Start the lesson by explaining that Thermodynamics is a branch of Physics that studies the relationships between heat, work, and energy in physical systems. Emphasize that gas pressure is a crucial concept in this field, as many laws of Thermodynamics apply when we understand how pressure works. A common example is the operation of car engines and refrigerators. Present the basic formula for pressure: P = F/A, where P is pressure, F is the normal force applied, and A is the area over which the force is distributed.

Curiosities

 Curiosity: Did you know that atmospheric pressure at sea level is approximately 101,325 Pa (Pascal)? This means that the force exerted by the atmosphere on each square meter of surface is about 10 tons! This pressure is fundamental to our survival as it keeps oxygen dissolved in blood and allows airplanes to fly stably.

Development

Duration: (40 - 50 minutes)

 Purpose: This stage of the lesson plan aims to deepen students' understanding of gas pressure, providing them with the theoretical and practical tools necessary to calculate pressure in different contexts. By addressing specific topics and solving guided problems, students will gain confidence and accuracy in applying the concepts learned.

Covered Topics

1. ️ Concept of Pressure: Explain that pressure is defined as the force exerted perpendicular to a surface divided by the area of that surface. The formula is P = F/A, where P is pressure, F is the normal force, and A is the area. 2.  Units of Measurement: Detail the units of pressure measurement, such as Pascal (Pa), atmosphere (atm), millimeters of mercury (mmHg), and bar. Explain how to convert between these units. 3.  Calculation of Pressure in Gases: Teach the formula for the pressure of an ideal gas, P = nRT/V, where P is pressure, n is the number of moles, R is the gas constant, T is the temperature in Kelvin, and V is the volume of the container. 4.  Practical Examples: Provide practical examples of how to calculate the pressure of a gas in different contexts, such as in a balloon, in a car tire, and in a gas cylinder. 5. ⚙️ Applications of Pressure: Discuss the importance of pressure in various technological and scientific applications, such as internal combustion engines, refrigerators, and airplanes.

Classroom Questions

1. 1. A balloon contains 2 moles of gas at a temperature of 300 K and a volume of 0.5 m³. What is the pressure exerted by the gas in the balloon? (Use R = 8.31 J/(mol·K)) 2. 2. Convert a pressure of 2 atm to Pascal (Pa). 3. 3. In a cylinder, the applied force is 1500 N and the area is 0.25 m². What is the pressure inside the cylinder?

Questions Discussion

Duration: (20 - 25 minutes)

 Purpose: This stage of the lesson plan aims to reinforce and consolidate students' understanding of the concept of gas pressure through detailed discussions of the resolved questions. Through active engagement and reflection, students will be able to apply the concepts learned in practical situations and understand the importance of precision in measurements and calculations related to pressure.

Discussion

•  Discussion of Questions:

1. A balloon contains 2 moles of gas at a temperature of 300 K and a volume of 0.5 m³. What is the pressure exerted by the gas in the balloon? (Use R = 8.31 J/(mol·K))

   To solve this question, use the ideal gas pressure formula: P = nRT/V. Substituting the provided values, we have:

   P = (2 moles) * (8.31 J/(mol·K)) * (300 K) / (0.5 m³)

   P = (4986 J/K) / (0.5 m³)

   P = 9972 Pa (Pascal)

   Therefore, the pressure exerted by the gas in the balloon is 9972 Pa.

2. Convert a pressure of 2 atm to Pascal (Pa).

   Knowing that 1 atm = 101325 Pa, the conversion can be done by multiplying the value in atm by 101325:

   2 atm * 101325 Pa/atm = 202650 Pa

   Thus, 2 atm is equivalent to 202650 Pa.

3. In a cylinder, the applied force is 1500 N and the area is 0.25 m². What is the pressure inside the cylinder?

   Using the pressure formula P = F/A, where F is the force and A is the area:

   P = 1500 N / 0.25 m²

   P = 6000 Pa

   Therefore, the pressure inside the cylinder is 6000 Pa.

Student Engagement

1.  Student Engagement:

1. Reflective Question: How would the pressure of a gas change if the volume of the container were reduced by half, keeping all other variables constant?

2. Group Discussion: If the temperature of a gas in a car tire increases, what happens to the pressure inside the tire? Explain based on the kinetic theory of gases.

3. Practical Application: Why is it important to check tire pressure before a long journey? How does pressure affect vehicle safety and efficiency?

4. Comparison of Units: Discuss the difference between the units of pressure (Pa, atm, mmHg, bar) and in what contexts each is most commonly used.

5. Conversion Challenge: Convert a pressure of 760 mmHg to atm and Pa, discussing each necessary step.

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to review and consolidate the main concepts covered throughout the lesson, reinforcing students' understanding and highlighting the practical application and importance of the studied theme. This moment of summary and reflection helps to solidify learning and connect theory to practice.

Summary

• Pressure is defined as the normal force applied to a surface divided by the area of that surface (P = F/A).
• The units of pressure measurement include Pascal (Pa), atmosphere (atm), millimeters of mercury (mmHg), and bar.
• The formula for the pressure of an ideal gas is P = nRT/V, where P is pressure, n is the number of moles, R is the gas constant, T is the temperature in Kelvin, and V is the volume of the container.
• Practical examples of pressure calculations in different contexts, such as balloons, car tires, and gas cylinders.
• The importance of pressure in technological and scientific applications, such as internal combustion engines, refrigerators, and airplanes.

The lesson connected the theory of gas pressure with practice through solving real problems and practical examples. Students were able to see how formulas and theoretical concepts are applied in everyday and technological situations, facilitating the understanding of the content and its practical relevance.

Gas pressure is a fundamental concept in many areas of our daily lives. For example, understanding how pressure works is essential for safety and efficiency in using car tires, in the operation of refrigerators, and in the functioning of engines. Additionally, atmospheric pressure is crucial for our survival and the operation of airplanes.