First Law of Thermodynamics

• Thermodynamic Process: A change in state of a system from an initial state to a final state.
• Work Done: Energy transferred from one system to another due to the application of force through a distance.
• Heat: Energy transferred between systems due to a difference in temperature.
• Internal Energy: Total energy of a system, including kinetic energy and potential energy of its microscopic constituents.
• Isothermal Process: A process in which the temperature remains constant.
• Adiabatic Process: A process in which no heat is transferred between the system and its surroundings.
• Cyclic Process: A process in which the system returns to its initial state.
• First Law of Thermodynamics Equation: For a closed system, the change in internal energy is equal to the heat added to the system minus the work done by the system.

Specific Concepts

• Sign Convention for Work: Positive work is done by the system on the surroundings and negative work is done by the surroundings on the system.
• Work Done by Gas Expansion: Positive work is done by a gas when it expands and negative work is done on the gas when it is compressed.
• Work Done by Piston: Positive work is done by the piston when it moves outward and negative work is done on the piston when it moves inward.
• Pressure-Volume Work: The work done by the gas during an isothermal expansion is given by the area under the curve on a pressure-volume diagram.
• Adiabatic Expansion and Compression: During an adiabatic expansion, the gas cools down and during an adiabatic compression, the gas heats up.