Class 11 Chemistry: Thermodynamics

1. Basic Concepts

• System and Surroundings
  • System: The part of the universe being studied.
  • Surroundings: Everything outside the system.
• Types of Systems
  • Open System: Can exchange both matter and energy with surroundings.
  • Closed System: Can exchange energy but not matter.
  • Isolated System: Cannot exchange energy or matter.
• State Functions
  • Depend only on the current state, not the path taken.
  • Examples: Internal energy, enthalpy, entropy.

2. First Law of Thermodynamics

• Internal Energy (U)
  • Total energy of a system (kinetic + potential energy).
• Heat (q)
  • Transfer of thermal energy between a system and surroundings.
• Work (w)
  • Energy transfer due to force acting over a distance.
• Mathematical Expression
  • ΔU = q + w

3. Enthalpy (H)

• Definition
  • State function related to heat transfer at constant pressure.
• Relationship to Internal Energy
  • H = U + PV
• Enthalpy Changes in Reactions
  • Exothermic: Release heat (ΔH < 0).
  • Endothermic: Absorb heat (ΔH > 0).

4. Calorimetry

• Measurement of Heat Changes
  • Using calorimeters.
• Specific Heat Capacity
  • Heat required to raise temperature of 1g of a substance by 1°C.

5. Hess's Law

• Enthalpy of Formation
  • Change when 1 mole of a compound is formed from elements in standard states.
• Hess's Law
  • Total enthalpy change is independent of the pathway.

6. Spontaneity of Reactions

• Entropy (S)
  • Measure of disorder or randomness.
• Second Law of Thermodynamics
  • Total entropy of the universe increases in spontaneous processes.
• Gibbs Free Energy (G)
  • Determines spontaneity at constant temperature and pressure.
• Relationship
  • ΔG = ΔH - TΔS

7. Applications of Thermodynamics

• Heat Engines
  • Convert heat into work.
• Refrigerators and Heat Pumps
  • Transfer heat from colder to hotter region.

By mastering these concepts, you will have a robust understanding of thermodynamics and its applications in chemical reactions and processes.