Thermodynamics , Basic Terminology System- Part of the | physicswallah27

Thermodynamics

, Basic Terminology

System-

Part of the universe under investigation.

Open System-

A system which can exchange both energy and matter with its surroundings.

Closed System-

A system which permits passage of energy but not mass, across its boundary.

Isolated system-

A system which can neither exchange energy nor matter with its surrounding.

Surroundings-

Part of the universe other than system, which can interact with it.

Boundary-

Anything which separates system from surrounding.

State variables-

The variables which are required to be defined in order to define state of any system i.e. pressure, volume, mass, temperature, surface area, etc.

State Functions-

Property of system which depend only on the state of the system and not on the path. Example: Pressure, volume, temperature, internal energy, enthalpy, entropy etc.

Intensive properties-

Properties of a system which do not depend on mass of the system i.e. temperature, pressure, density, concentration,

Extensive properties-

Properties of a system which depend on mass of the system i.e. volume, energy, enthalpy, entropy etc.

Process-

Path along which state of a system changes.

Isothermal process-

Process which takes place at constant temperature

Isobaric process-

Process which takes place at constant pressure

Isochoric process-

Process which takes place at constant volume.

Adiabatic process-

Process during which transfer of heat cannot take place between system and surrounding.

Cyclic process-

Process in which system comes back to its initial state after undergoing series of changes.

Reversible process-

Process during which the system always departs infinitesimally from the state of equilibrium i.e. its direction can be reversed at any moment.

Irriversible Process-

This type of process is fast and gets completed in a single step. This process cannot be reversed. All the natural processes are of this type.