CHAPTER 10: THE GAS LAWS

Gases are unique in that they have no fixed shape or volume—they expand to fill any container. Their behavior is governed by three variables: pressure (P), volume (V), and temperature (T). The Gas Laws describe the relationships between these variables. Understanding these laws is essential for explaining everything from weather balloons to refrigeration.

10.1 IMPORTANT CONCEPTS AND UNITS

Before diving into the laws, we must establish the proper units and scales.

10.1.1 Pressure (P)

• Definition: Force per unit area.
• SI Unit: Pascal (Pa) = 1 N/m².
• Other common units:
  • Atmospheres (atm): 1 atm = 101,325 Pa (approximately 1.01 × 10⁵ Pa).
  • cm or mm of mercury (Hg): Standard atmospheric pressure = 76 cm Hg = 760 mm Hg.
  • Bars: 1 bar = 10⁵ Pa (close to 1 atm).

10.1.2 Volume (V)

• Definition: The space occupied by the gas.
• SI Unit: Cubic metre (m³).
• Other common units: Litres (L) or cm³. 1 L = 10⁻³ m³, 1 cm³ = 10⁻⁶ m³.

10.1.3 Temperature (T) - The Kelvin Scale

For all gas laws, temperature must be in Kelvin (K), not Celsius (°C). The Kelvin scale starts at absolute zero (-273°C), the theore