What term describes the expansion or contraction of a gas without a change in temperature?

The term that describes the expansion or contraction of a gas without a change in temperature is adiabatic. In an adiabatic process, the system is thermally insulated so that any changes in pressure and volume occur without heat transfer to or from the surroundings. This means that the gas can either expand or contract, and while its internal energy may change, the temperature remains constant throughout the process.

In contrast, isothermal processes involve changes occurring at a constant temperature, where heat exchange with the environment allows for temperature stabilization. Isochoric processes happen at a constant volume, meaning the gas cannot expand or contract, and any heat added increases the pressure instead. Hyperbaric refers to conditions of high pressure but does not specifically relate to temperature changes of gases during expansion or contraction. Thus, adiabatic is the most accurate term for gas behavior characterized by expansion or contraction without temperature change.