Definition of system and surroundings

Definition of System and Surroundings

In thermodynamics and physical chemistry, the concepts of system and surroundings are fundamental to understanding how energy and matter interact.

What is a System?

A system is the specific part of the universe that is under study or consideration. It can be as simple as a chemical reaction in a test tube or as complex as the entire Earth’s atmosphere.

Systems are categorized into the following types:

• Open System: Can exchange both energy and matter with its surroundings.
• Closed System: Can exchange only energy, but not matter, with its surroundings.
• Isolated System: Neither energy nor matter is transferred between the system and its surroundings.

What are Surroundings?

The surroundings include everything outside the system that can interact with it. This may involve the container, the air around the system, or the environment where the system exists.

Boundary Between System and Surroundings

The boundary separates the system from its surroundings. It can be real or imaginary and may be fixed or movable depending on the nature of the system being studied.

Example

Imagine a pot of water boiling on a stove. The water within the pot represents the system, whereas the pot itself, the stove, and the surrounding air make up the surroundings. Heat flows from the stove through the pot’s surface (the boundary) into the water, leading to boiling.

• System: The part of the universe being studied.
• Surroundings: All matter and space external to the system.
• Boundary: The dividing line between the system and surroundings.