Lesson 11

Temperature Scales

• Three temperature scales: Kelvin, Celsius, Fahrenheit.
• Kelvin to Celsius conversion: ( K = C + 273 )
• Celsius to Kelvin conversion: ( C = K - 273 )
• Celsius to Fahrenheit conversion: ( C = (F - 32) \times \frac{5}{9} )
• Fahrenheit to Celsius conversion: ( F = (C \times 1.8) + 32 )

States of Matter and Temperature

• Temperature affects state: solid, liquid, gas.
• Melting point: solid to liquid.
• Boiling point: liquid to gas.
• Condensation point: gas to liquid (same as boiling point).
• Freezing point: liquid to solid (same as melting point).

Pressure Units

• Pressure formula: ( P = \frac{F}{A} )
• Effect of area on pressure: Increasing area decreases pressure; decreasing area increases pressure.
• Common pressure units:
  • 1 atm = 760 mmHg = 760 torr = 1 bar = 100 kPa = 1,033 cm H₂O = 14.7 lb/inch²
  • 1 mmHg = 1.36 cm H₂O
  • 1 cm H₂O = 0.74 mmHg

Avogadro's Number

• 1 mole of a gas = 6.023 ( \times 10^{23} ) atoms.
• Molecular weight of a gas in grams = weight in g for 1 mole.
• Helium: Molecular weight = 4 g, contains ( 6.023 \times 10^{23} ) atoms.
• Diatomic gases (e.g., O₂): Atomic weight x 2. Oxygen = 16 g, O₂ = 32 g (1 mole contains ( 2 \times 6.023 \times 10^{23} ) atoms).