THERMODYNAMICS : BASIC TERMINOLOGY

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.