Question

When the system does not exchange heat with the surroundings, the process is (a) isothermal (b) adiabatic (c) thermal (d) isochoric.

Short answer

(b) adiabatic

Step-by-step solution

Identify the Thermodynamic Process

First, understand that thermodynamic processes can be categorized based on how they exchange energy with the surroundings. The key term to focus on here is 'does not exchange heat'.

Review the Definitions

Next, review the definitions of each term given in the options: (a) Isothermal processes occur at constant temperature, (b) Adiabatic processes do not exchange heat with the surroundings, (c) 'Thermal' is not a process, it is an adjective related to heat, (d) Isochoric processes occur at constant volume.

Choose the Correct Answer

Since the question specifies that the system does not exchange heat with the surroundings, the correct term is 'adiabatic'. This matches definition (b).

Key concepts

Thermodynamics

Thermodynamics is the branch of physics that deals with the relationships between heat and other forms of energy. In essence, it describes how thermal energy is converted to and from other forms of energy and how it affects matter. It involves the study of energy, entropy, and the laws of thermodynamics which govern the physical processes of transferring energy.

Within this field, various processes describe how a system exchanges energy with its surroundings. An adiabetic process is just one example of many thermodynamic processes, others include isothermal, isobaric, and isochoric processes. Understanding these terms is crucial in a wide range of scientific and engineering applications, from power generation to refrigeration, as well as in natural phenomena.

Isothermal Process

An isothermal process is a thermodynamic process that occurs at a constant temperature. The term 'isothermal' itself means 'equal temperature.' During an isothermal process, a system may exchange heat with its surroundings to ensure that the temperature remains constant.

In an isothermal expansion or compression of an ideal gas, the amount of work done by the gas is exactly balanced by the heat exchanged with the environment, according to the first law of thermodynamics. In practical terms, think of an isothermal process as occurring 'so slowly' that the heat transferred does not lead to a temperature change. This concept is vital in understanding engines and refrigerators, which operate under cycles involving isothermal changes.

To physically realize an isothermal process, the system must be in contact with an external reservoir and able to conduct heat efficiently. It's important to note that while the temperature remains constant, other parameters, like the volume or pressure of the gas in the system, can change.

Isochoric Process

Isochoric processes, also known as isovolumetric processes, occur when a system's volume remains constant. 'Isochoric' is derived from 'iso-' meaning 'same,' and '-choric' meaning 'space or volume.' In this type of process, the work done by or on the system is zero, because work is a product of pressure and a change in volume, and thus for any process where volume does not change, work done is zero.

An example of an isochoric process is the heating or cooling of air in a sealed, rigid container. As the temperature of the air changes, so does its pressure; this relationship is described by the ideal gas law. However, since the volume doesn't change, no work is performed on or by the system. This concept is relevant in understanding how energy is conserved in systems where volume remains a constant while other variables change.