Lecture on Air Pressure and Breathing Process

Introduction to Air Molecules

• Imaginary ability to see all air molecules
• Visualization: Crowded but still perceivable
• Using a glass jar to trap some air molecules

Glass Jar Experiment

• Glass jar with a small opening (elongated neck)
• Comparison between inside and outside of the jar
• Created a purple box to represent a similar section of the atmosphere
• Molecules in both areas bouncing off each other randomly
• Increased collision frequency → Increased air pressure
• Atmospheric air pressure usually measured around 760 mmHg
• Jar’s initial pressure same as atmospheric: 760 mmHg

Molecule Specifics

• Air composition: mostly nitrogen (N₂) and some oxygen (O₂)
• Random movement and collisions of molecules within the jar

Adjusting Jar's Volume

• Lowering the jar’s bottom, increasing its volume
• With the jar entrance closed, increased volume leads to decreased pressure (fewer collisions)
• Pressure drops to 757 mmHg (lower than the outside’s 760 mmHg)

Opening the Jar

• Molecules enter the jar through collisions when the entrance opens
• Increased number of molecules inside due to additional space and less density
• Over time, the internal pressure increases back to 760 mmHg

Reverting to Original Volume

• Raising the jar’s bottom back to original position
• Reduced volume inside the jar
• Increased internal collisions, and pressure rises to 763 mmHg (higher than outside’s 760 mmHg)
• Opening the entrance again leads to more molecules exiting than entering
• Pressure inside drops back to 760 mmHg

Relating the Jar to Human Lungs

• Analogous transformation of the jar into human lungs model
• Right and left lungs with trachea as the entrance
• Process of inhaling and exhaling
• Inhaling: Increasing volume, decreasing pressure, air moves in
• Exhaling: Decreasing volume, increasing pressure, air moves out

Conclusion

• Every breath involves small changes in volume and pressure
• Understanding basic principles of air pressure is crucial for comprehending the breathing process