# System and surrounding

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A system, as it is defined in physics or chemistry, is nothing more than a collection of objects (or smaller systems) that can be identified. Usually, the word system refers to a collection that makes thinking about a problem more convenient. The surrounding is everything else that is not the system defined. For example, if the system being studied is a house, the surrounding would be everything else that is not the house (other houses, the neighbourhood, the general environment around the house, etc.). Systems can be described in three different ways[1]:

1. Isolated: this is a system in which no matter or energy is being exchanged with the surroundings.
2. Closed: this is a system in which only energy is being exchanged with the surroundings.
3. Open: this is a system in which both matter and energy is being exchanged with the surroundings.

Often, the most convenient system is an isolated system, one where outside influences can be ignored (either because they cancel out or because outside influences are negligible). For example, two balls rolling across a smooth surface to strike each other can be considered an isolated system, while two balls rolling across a gravel path or thick carpet are influenced by friction originating from outside the system and therefore are not an isolated system.

While anything can be a system, much of the study of physics and chemistry is about figuring out which systems are useful to consider in studying a particular property or relationship of items within the system.

Figure 1. This depicts the difference between isolated, closed and open systems. [2]
Examples of Systems
• Figure 2. This is an open system. The system is the pan and the surrounding is the kitchen.[2]
• Figure 4. This is a closed system. The system is the pan/lid and the surrounding is the kitchen.[2]
Figure 4. This is an isolated system. The system is the thermos and the surrounding is the kitchen.[2]