Open,closed,and isolated systems.

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Open, closed, and isolated systems are defined by their ability to exchange matter and energy. An open system can exchange both, while a closed system exchanges only energy and an isolated system exchanges neither. Humans are classified as open systems because they can exchange both energy and matter with their environment, such as through respiration. In chemical reactions, understanding these systems helps clarify how different elements and compounds interact. The distinctions between these systems are crucial for studying thermodynamics and chemical processes.
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I know how they differ from one another, but what are they physically? Are humans closed systems, because we are able to exchange energy between us and our surroundings, but what I am trying to learn is the kinds of systems in chemical reactions: which elements react to form different systems, which molecules/compounds are open/closed/isolated...?
 
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An open system can exchange matter and energy through its boundary. A closed system can exchange energy but NOT matter through its boundary. An isolated system can exchange neither energy nor matter through its boundary.

Humans are open systems, and not closed systems like you mentioned. We can exchange energy with our surroundings, but we can also exchange matter. For example, when we breathe, we are changing the number of atoms/molecules is our bodies.
 
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