Answer: open system.
- A open system
- B closed system
- C isolated system
- D adiabatic wall
Correct answer: A. open system
Explanation: An open system exchanges both matter and energy - for example, water boiling in an open beaker.
Isothermal expansion follows a gentler curve (heat flows in to keep T constant) while adiabatic expansion drops in pressure more steeply (no heat exchange, so internal energy and temperature fall as the gas does work).
Concept context
Study energy changes in chemical reactions. Understand enthalpy, entropy, Gibbs free energy, and the laws of thermodynamics that decide whether a reaction will occur spontaneously or not.