Chemical 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.

Irreversible 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.