Problem 21 - Chemistry The Central Science

Question

(a) Which of the following cannot leave or enter a closed system: heat, work, or matter? (b) Which cannot leave or enter an isolated system? (c) What do we call the part of the universe that is not part of the system?

Step-by-Step Solution

Answer

(a) In a closed system, matter cannot enter or leave the system, but heat and work can be exchanged with the surroundings. (b) In an isolated system, neither matter, heat, nor work can leave or enter the system. (c) The part of the universe that is not part of the system is called the surroundings.

Step 1: (a) Closed System Definition

A closed system is a system that cannot exchange matter with its surroundings, but it can exchange energy in the form of heat and work.

Step 2: (a) Entities that cannot enter or leave a Closed System

In a closed system, matter cannot enter or leave the system. However, heat and work can be exchanged with the surroundings.

Step 3: (b) Isolated System Definition

An isolated system is a system that cannot exchange energy or matter with its surroundings.

Step 4: (b) Entities that cannot enter or leave an Isolated System

In an isolated system, neither matter, heat, nor work can leave or enter the system.

Step 5: (c) Term for the part of the universe not part of the system

The part of the universe that is not part of the system is called the surroundings.

Key Concepts

Closed System

In thermodynamics, a closed system is a fascinating concept with specific restrictions. It is defined as a setup where matter cannot cross the system boundaries. This means that no particles like atoms or molecules can enter or leave the system.
However, energy, manifested in forms such as heat and work, is allowed to be exchanged with the surroundings. This makes a closed system quite versatile, as it can interact energetically without any change in its matter content.
Understanding closed systems helps us consider scenarios like a sealed pot heating on a stove where steam (matter) does not escape, but heat and work (via pressure) can interact with the environment.

• Boundaries- Keep matter in, allow energy out (or in).
• Energy exchange - Achieves thermal equilibrium with surroundings.
• Common examples - Pressure cookers or radiator systems.

It's important to remember that in reality, maintaining entirely closed systems can be challenging due to eventual tiny matter exchanges at microscopic levels.

Isolated System

An isolated system takes constraints to a higher level in thermodynamics. These systems are perfect, albeit theoretical, examples where neither energy nor matter can cross the boundaries.
They are completely self-contained and impervious to outside influences. This means no heat is transferred, no work is done, and no matter is exchanged with the surroundings.
Examples can include a thermos flask or an insulated container, although in ideal conditions these would need absolute isolation, which is practically challenging but conceptually illuminating.

• Tightest restrictions - Energy and matter both stay within.
• No interaction - Independent of surroundings entirely.
• Real-world challenges - Achieving true isolation is practically impossible.

Understanding isolated systems is useful for theoretical investigations in thermodynamics, helping us model situations without external interference.

Surroundings

In thermodynamics, the surroundings comprise everything in the universe outside the considered system. The universe can be thought of as divided into the system of interest and everything else.
The surroundings act as the environment with which a system exchanges energy and matter, though this depends on the nature of the system (open, closed, or isolated).
Analyzing interactions between a system and its surroundings is crucial as changes in the system often send effects spilling into the surroundings.

• Everything else - The part outside the system of focus.
• System interactions - Defines energy or matter exchange limits with different types of systems.
• Influential role - Affects and is affected by changes in the system.

By understanding the concept of surroundings, we can better grasp how systems influence and are influenced by the external environment, giving valuable insights in fields like engineering and environmental science.