Thermodynamics: Isothermal Expansion and Energy Transfer

Work and Internal Energy

Isothermal Expansion

• Isothermal expansion is a process where a system expands at a constant temperature.
• In an isothermal expansion, the system absorbs heat from the surroundings and does work on the surroundings.
• The internal energy (U) of the system remains constant, as the heat absorbed (Q) is equal to the work done (W) by the system:
  • ΔU = Q - W = 0
  • Q = W
• The work done by the system is given by:
  • W = nRT ln(V2/V1)
  • where n is the number of moles of gas, R is the gas constant, T is the temperature, and V1 and V2 are the initial and final volumes, respectively.

Energy Transfer

• Energy transfer occurs when energy is transferred from one system to another.
• There are two types of energy transfer:
  • Heat transfer (Q): energy transfer due to a temperature difference between the system and its surroundings.
  • Work (W): energy transfer due to a force applied to the system.
• The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another:
  • ΔE = Q - W
  • where ΔE is the change in internal energy of the system.
• Energy transfer can occur through various means, including:
  • Conduction: direct contact between particles
  • Convection: transfer of energy through fluid motion
  • Radiation: transfer of energy through electromagnetic waves