System

A thermodynamic system is a collection of matter which has distinct boundaries.
Or,
A real or imaginary portion of universe which has distinct boundaries is called system.
Or,
A thermodynamic system is that part of universe which is under thermodynamic study.

For example:
A balloon filled with water
A beaker filled with water

Types of system
There are three types of thermodynamic systems.

1. Open system
2. Closed system
3. Isolated system

1. Open system
An open system is one in which both mass & energy transfer takes place across the boundaries.

• An open tank of water.

2. Closed system
A closed system in which there is no transfer of mass takes place across the boundaries of system but energy transfer is possible.

• A gas in a balloon.

3. Isolated system
An isolated system is that in which there is no transfer of mass & energy takes place across the boundaries of system.

• A thermo flask containing hot or cold liquid.

Macroscopic properties
All the properties of a system in bulk which are easily measurable are known as macroscopic properties.

Types of macroscopic properties
Macroscopic properties can be divided into two main classes.

1. Intensive properties
2. Extensive properties

1. Intensive properties
Macroscopic properties of a system which are independent of mass are known as intensive properties, whatever is the mass but properties remain unchanged.
For example: melting point, boiling point, density, temperature, pressure, viscosity.

Extensive properties
Macroscopic properties of a system which are strictly dependent on their mass or quantity of matter are known as extensive properties.

• If mass is halved the property will also be half. For example: volume, mole, mass, enthalpy, internal energy, kinetic energy.