Question

(a) What is meant by the term system in thermodynamics? (b) What is a closed system? (c) What do we call the part of the universe that is not part of the system?

Short answer

In thermodynamics, a system is a part of the universe chosen for study and analysis, typically containing a substance (gas, liquid, or solid) with macroscopic properties such as pressure, temperature, and volume. A closed system is a type of system that allows energy transfer (heat and work) across its boundaries, but not the transfer of matter. The part of the universe not included in the system is called the "surroundings" or "environment," consisting of everything external to the system that can interact with it. Together, the system and its surroundings form the entire universe.

Step-by-step solution

Definition of a System in Thermodynamics

In thermodynamics, a system is a part of the universe that we choose to study, analyze, and observe. It is typically selected based on the specific processes or interactions we are interested in examining. The system can be a gas, liquid, or solid, and it can have a fixed or changing volume, mass, and energy components. Systems are used to describe macroscopic properties of the substances inside them such as pressure, temperature, and volume.

Definition of a Closed System

A closed system is a specific type of thermodynamic system that allows energy transfer in the form of heat and work across its boundaries, but it does not permit the transfer of matter. In simpler terms, a closed system means that no mass is allowed to enter or leave the system, but energy can be exchanged between the system and its surroundings.

Definition of the Part of the Universe That Is Not Part of the System

In thermodynamics, the part of the universe that is not included in the system being studied is called the "surroundings" or "environment". Surroundings consist of everything external to the system that can possibly interact with it. Together, the system and its surroundings form the entire universe. When studying a problem in thermodynamics, it is essential to distinguish between the system and its surroundings, as it allows us to analyze energy transfer and other interactions between the two entities.

Key concepts

System in Thermodynamics

Understanding the concept of a 'system' in thermodynamics is fundamental to grasping the principles of the science. Imagine drawing an imaginary or physical line around any group of matter; what you've enclosed is called a 'system.' It's a specific portion of the material universe chosen for analysis, often involving substances like gases, liquids, or solids. In our studies, we look at how this system behaves—changes in its pressure, temperature, and volume, for example.
Thermodynamics isn't just about individual substances, though; it's how these substances interact with the environment around them.

The Purpose of a System in Studies

The choice of a system is purpose-driven, focused on the processes and interactions that are of interest. By defining a system, scientists can create models to predict behaviors and outcomes, even in complex situations like engine functionality or weather patterns. This approach simplifies the universe into more manageable chunks.

System Boundaries

Boundaries can be real, like the walls of a container or theoretical, such as the borders of air around a flying airplane. They dictate what's included in studies and what's excluded, essential for energy balance calculations and other thermodynamic considerations.

Closed System

A 'closed system' in thermodynamics has a very specific meaning. It's akin to a container that's sealed tightly—nothing gets in or out, at least in terms of matter. However, unlike an actual sealed container, energy such as heat or work can still cross the system's boundaries.

Energy Transfer

While closed systems keep their matter consistent, they can still experience changes in energy. Imagine boiling water in a pot with a lid; the steam (matter) is contained, but the heat (energy) can escape if the lid isn't perfectly insulated.

Real-world Applications

This concept is key in many engineering scenarios—think of a refrigerator or air conditioning system. These mechanisms rely on the principles of a closed system to control temperature without losing refrigerant. In scientific research, using closed systems simplifies experiments by eliminating variables related to the exchange of matter.

Surroundings in Thermodynamics

Beyond the concept of a thermodynamics system is its 'surroundings' or environment. Essentially, it's everything outside the system and can include other systems, the air, and indeed, any matter or energy that isn't part of the system being studied. The surroundings can influence the system in profound ways—like the ice-cold air causing a car's engine to take longer to start.
The interaction between a system and its surroundings helps dictate many natural processes.

Interdependent Relationship

Understanding this dynamic is crucial for solving thermodynamics problems. It’s a dance of energy exchange where the two can impact each other's state.

Importance in Calculations

For accurate thermodynamic calculations, scientists must consider the system and its surroundings. Overlooking the environmental impact can lead to incomplete or incorrect conclusions, akin to trying to predict the weather without considering the ocean's influence on the climate.