Properties of Gas

Introduction

• Lecture by Chad from Chad's Prep.
• Focus on distinguishing gas from liquids and solids.
• Discussion on pressure, a key property of gas.

Distinguishing Gases from Liquids and Solids

• Gases:
  • No definite shape or volume.
  • Expand to fill the shape and volume of their container.
• Liquids:
  • Definite volume but no definite shape.
  • Take the shape of the container without expanding to fill entire volume.
• Solids:
  • Definite shape and volume.
• Gases are mostly empty space, making them expandable and compressible.
  • Liquids and solids have closely packed molecules, making them less compressible.

Properties of Gases

• Compressibility:
  • Gases are easily compressible due to empty space between molecules.
  • Pressure affects volume significantly, unlike solids and liquids.
• Mixing:
  • Gases can mix with each other in any proportion.
  • Different from liquids (e.g., oil and water do not mix).

Understanding Pressure

• Pressure Definition:
  • Force per unit area (SI unit: Pascal).
  • Pascal is a Newton per meter squared.
• Common Units of Pressure:
  • Atmospheres (atm):
    • Standard air pressure at sea level.
  • Millimeters of mercury (mmHg):
    • Historical unit from barometers.
    • 1 atm = 760 mmHg.
  • Tor:
    • Equivalent to mmHg at Earth's surface.
  • Pascal:
    • 1 atm = 101,325 Pa (or 101.325 kPa).
  • PSI (pounds per square inch):
    • Common in the US but not in chemistry.

Pressure and Area Relationship

• Pressure is directly proportional to force and inversely proportional to area.
  • Smaller area increases pressure (e.g., knife vs. marker on watermelon).

Unit Conversions

• Common Conversions:
  • 1 atm = 760 Tor or mmHg.
  • 1 atm = 101,325 Pascal.
  • For quick estimates: 1 atm ≈ 100,000 Pascal.
• Conversion Example:
  • Converting 2 atm to Tor: 2 x 760 = 1520 Tor.
  • Converting 2 atm to Pascal: 2 x 101,325 = 202,650 Pascal.

Conclusion

• Understanding gases involves examining their properties, pressure relationships, and behavior in mixing.
• Practical exercises and further practice available in Chad's General Chemistry Master Course.

Additional Resources

• Visit chadprep.com for comprehensive study resources on various science topics.