In an isobaric process, what happens to the pressure?

• A. Volume remains constant
• B. Temperature remains constant
• C. Heat exchanged is zero
• D. Pressure remains constant

Answer: (D)

In an isobaric process the pressure stays constant. The term comes from Greek roots meaning equal pressure, so the gas adjusts its volume as heat is added or removed to keep the pressure the same. In a piston scenario, heating the gas makes the piston move outward to maintain the same external pressure, so volume changes while pressure remains fixed; cooling does the opposite. For an ideal gas, P V = n R T shows that with P constant, volume is proportional to temperature, which explains the relationship between V and T in this process. The other statements describe different processes: constant volume is an isochoric process, constant temperature is an isothermal process, and zero heat exchange is an adiabatic condition, not necessarily isobaric.