Closed System in Chemistry: Definition & Example

Lesson Transcript
Instructor: Nathan Crawford

Nathan, a PhD chemist, has taught chemistry and physical science courses.

This lesson provides a basic definition of a closed system from thermodynamics. Examples are included to provide students with illustrations of closed systems that are encountered within chemistry.

Definition of a Closed System

You have probably put soft drinks in a cooler under ice to keep them cold. When the lid of the cooler is closed, nothing can get in or out, and the insulated walls appear to keep all of the contents nice and frosty. However, if enough time passes, the ice does eventually melt into water. This is an excellent example of a closed system. What is a system, and, more to the point, what is a closed system? How are closed systems used in chemistry?

Cooler with iced soft drinks
Cooler with iced soft drinks

The concept of a system comes from thermodynamics, a branch of physics that studies the transfer of energy between objects and their surroundings. A system within thermodynamics is defined as part of the physical universe. The system could be a car engine, a mass of air in the atmosphere, or even a soft drink can. Systems are separated from the rest of the physical universe (or the surroundings) by a boundary that can real (such as the walls of a cooler) or imaginary, used to focus on a specific part of a complicated situation, such as the combustion cylinder within an engine.

An engine with cylinders shown
An engine with cylinders shown

Systems are classified in three basic ways: open, closed, or isolated. These describe how energy and matter are allowed to enter or leave the system. Within an open system, matter and energy freely cross the boundary of the system. For example, the Earth can be considered an open system because sunlight reaches the surface of our planet, meteorites can enter our atmosphere, and we can send objects out into space. Closed systems, like the closed cooler described previously, allow energy to cross the boundary of the system, but matter is prevented from being added to or removed from the system. Isolated systems allow neither matter nor energy to cross the boundary of the system.

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  • 0:01 A Closed System
  • 1:50 Examples
  • 3:10 Lesson Summary
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The Earth, an open system
The Earth, an open system

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