A “system” refers to a particular portion of the universe or a collection of components chosen for observation and study. Scientists define these systems to simplify complex phenomena, allowing for focused analysis within their boundaries. Establishing these boundaries is a fundamental step in any scientific investigation, as it determines what is considered part of the observation and what belongs to the surrounding environment.
Understanding Open Systems
An open system freely exchanges both matter and energy with its surroundings. Physical substances, such as atoms or molecules, move into or out of the system, alongside energy transfers like heat or light. Its boundaries are permeable, allowing for a continuous flow of inputs and outputs.
Living organisms serve as examples of open systems. A human body constantly exchanges matter by taking in food and oxygen, and releasing waste products and carbon dioxide. It also exchanges energy through metabolic processes, releasing heat to the environment while performing work. A pot of water boiling on a stove illustrates this, exchanging heat with the burner and releasing steam into the air.
Understanding Closed Systems
A closed system exchanges energy with its surroundings but prevents matter transfer. Energy, such as heat or light, can readily cross the system’s boundaries, but no physical substances can enter or leave. The boundaries of a closed system contain its contents, ensuring the mass within remains constant.
A sealed terrarium provides a good example. Light and heat pass through its glass walls, allowing plants to photosynthesize and influencing the internal temperature. The soil, water, and gases remain contained within, cycling internally without external material input or output. A chemical reaction in a tightly sealed flask exchanges heat with the environment but maintains a fixed amount of reactants and products inside.
Core Differences Between System Types
The fundamental distinction between open and closed systems lies in their interaction with the surroundings, specifically concerning matter exchange. Open systems allow both matter and energy to cross their boundaries, meaning their composition can change and total mass is not necessarily conserved. Closed systems are impermeable to matter, so their total mass remains constant.
Energy can freely flow across the boundaries of both system types, but only closed systems maintain a fixed quantity of physical substance. This difference profoundly impacts how conservation laws apply: mass is conserved within a closed system, but changes for an open system as it interacts with its environment.
Real-World Applications and Examples
In biology, a single cell functions as an open system, continuously taking in nutrients, expelling waste, and converting energy. The human body operates as a complex open system, relying on constant exchange with its environment for survival.
Chemistry frequently utilizes both system types. Many everyday chemical reactions, such as burning a candle in an open room, occur in open systems where reactants and products exchange with the air. Laboratory reactions might be conducted in sealed containers, approximating a closed system to control the amount of substances involved.
In environmental science, Earth is an open system regarding energy, receiving solar radiation and radiating heat back into space. However, it is largely treated as a closed system regarding matter, given the minimal exchange of physical substances with outer space.