Closed Systems and Isolated Systems
Closed systems and isolated systems are key concepts in thermodynamics, which is the study of energy transfer within defined boundaries. A closed system allows for the exchange of energy but not matter with its surroundings. For example, a thermos can keep a beverage warm by transferring heat but does not allow the drink itself to escape. In contrast, an isolated system neither exchanges energy nor matter with the environment. While a perfectly isolated system is theoretical, the universe is often considered as such. Both systems adhere to the conservation of energy principle, which states that energy within an isolated system remains constant and can only change forms. Additionally, concepts like entropy and equilibrium come into play, where systems tend to move toward greater disorder and an even energy distribution. Understanding these distinctions enhances comprehension of how energy operates within different system boundaries, important for fields such as physics, engineering, and environmental science.
Closed Systems and Isolated Systems
FIELDS OF STUDY: Thermodynamics
ABSTRACT: This article discusses two of the three types of thermodynamic system, with examples of how they behave. Closed systems cannot transfer matter across their boundaries, but they can transfer energy. Isolated systems can transfer neither matter nor energy.
principal terms
- conservation of energy: a law of physics that states that within an isolated system, the amount of energy remains constant; energy can be neither created nor destroyed, only transformed.
- entropy: a measure of how close a system is to equilibrium; also described as the amount of disorder in a system.
- equilibrium: the condition of a thermodynamic system in which there is no energy flow.
- open system: a system in which both matter and energy can be exchanged between the system and its surroundings.
- system boundary: the border of the system being considered.
Thermodynamic Systems
Thermodynamics is the study of the propagation of energy, usually in the form of heat, within a system boundary. Systems can be open, closed, or isolated. An open system is one that can exchange both matter and energy across its boundary. A closed system allows only energy transfer. An isolated system allows neither energy nor matter to be transferred. A perfectly isolated system is not really possible, although the universe itself is sometimes thought of as an isolated system. However, one might imagine an impossibly good thermos, capable of maintaining a beverage at one exact temperature forever, with no heat ever escaping; this would be an isolated system. Isolated systems follow the law of conservation of energy, meaning within them, energy can never be created or destroyed. It can only change its form. For example, if one were to put warm water and an ice cube in this ideal thermos, the ice cube would melt, and the water would cool down, but the total amount of heat in the thermos would stay the same.
The example of the ice cube melting inside the thermos is also an example of entropy, the tendency of systems to move toward a state of equilibrium. (Sometimes this is described as moving toward a state of greater disorder.) Equilibrium means the energy in a system is evenly distributed. In the example of the ice water, at first the water will be warmer and the ice cube will be colder. Eventually, however, the ice cube will melt and the system will reach a state where it is all water of one temperature. In real life, thermoses are not isolated systems, but closed systems. Therefore, because of the transfer of energy through the wall of the thermos (that is, across the system boundary), the water inside the thermos will eventually reach the same temperature as the space outside the thermos. This is an example of how closed systems in contact (the thermos and the space around it) reach equilibrium between one another.
Bibliography
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