Problem 21 - Chemistry: The Central Science in SI Units, Global Edition

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 leave or enter the system. (b) In an isolated system, "heat, work, and matter" cannot 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 one in which mass (matter) cannot enter or leave the system but energy (heat and work) can be transferred across its boundary.

Step 2: (a) Closed System: Identification

In a closed system, matter cannot leave or enter the system. Therefore, the answer for part (a) is "matter."

Step 3: (b) Isolated System: Definition

An isolated system is one in which neither mass nor energy can be transferred across its boundary. It is completely separated from its surroundings.

Step 4: (b) Isolated System: Identification

In an isolated system, no heat, work, or matter can leave or enter the system. Therefore, the answer for part (b) is "heat, work, and matter."

Step 5: (c) Universe: System and Surroundings

In thermodynamics, the universe consists of two parts: the system under study and the surroundings. The surroundings encompass everything else that lies outside the system and can interact with it.

Step 6: (c) Universe: Terminology

We call the part of the universe that is not part of the system the "surroundings."

Key Concepts

Closed System

A closed system is a fundamental concept in thermodynamics. It describes a system where no matter can enter or leave. This might sound a bit limiting, but energy can still cross the boundaries. This includes both heat and work.

Here's how it works:

• No exchange of matter: The mass within the system remains constant at all times. So, if a scenario describes a system without any matter coming in or going out, it is likely closed.
• Energy exchange: Energy is free to move in and out, either in the form of heat or work. This allows for many dynamic processes to happen, even within the closed boundaries.

In practical examples, think of a closed water bottle. You can't pour more water in or out without opening the cap, but if the bottle is exposed to the sun, it might heat up due to energy transfer.

Isolated System

An isolated system takes things a step further than a closed system. In this type of system, neither matter nor energy can cross the boundaries. It is completely insulated and separated from its surroundings.

Characteristics of an isolated system include:

• No matter exchange: Just like a closed system, no matter goes in or out.
• No energy exchange: Unlike a closed system, even energy in the form of heat or work cannot be transferred across its boundaries.

An easy way to remember this is to think of an ideal thermos flask. An ideal thermos would not allow the heat to escape or enter, keeping your drink at the same temperature, no matter what's happening outside.

Surroundings

The surroundings refer to everything that is outside of the system being studied in thermodynamics. When considering problems in thermodynamics, we often describe the system and then everything else that it's interacting with as the surroundings.

Important points about surroundings:

• The surroundings can interact with the system, affecting or being affected by energy or matter transfer, depending on the system’s classification (closed, open, or isolated).
• Understanding surroundings helps to predict how the system will behave. For instance, if a system is transferring heat to its surroundings, the temperature might change accordingly.

Imagine you were testing a car engine (the system). The air, road, and even the environment around the car would be considered as the surroundings.