1. Chemical systems

A chemical system consists of a certain quantity of matter occupying a total volume V bounded by an envelope.

Exchanges between the system and its environment (the outside world) take place by transfer through the envelope.

Modeling the thermodynamic properties of chemical systems is based, in the general case, on three types of exchange:

• exchange of mechanical work by volume, linked to the system's volume variation; this work is therefore zero when the envelope is rigid;

• heat transfer through the envelope ;

• exchange of matter; in this case, the system is open, in the opposite case, it is closed.

In the absence of any exchange, the system is isolated.