Ch.5 - Thermochemistry

Brown - Chemistry: The Central Science 14th Edition

Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook

Brown 14th Edition

Ch.5 - Thermochemistry

Problem 8a

Chapter 5, Problem 8a

Imagine a container placed in a tub of water, as depicted in the accompanying diagram. (a) If the contents of the container are the system and heat is able to flow through the container walls, what qualitative changes will occur in the temperatures of the system and in its surroundings? From the system's perspective, is the process exothermic or endothermic?

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Identify the system and surroundings: The system is the contents of the container, and the surroundings are the water in the tub.

Determine the direction of heat flow: Since heat can flow through the container walls, it will move from the warmer region to the cooler region.

Analyze the temperature changes: If the system is initially warmer than the surroundings, heat will flow out of the system, causing the system's temperature to decrease and the surroundings' temperature to increase.

Determine the nature of the process: From the system's perspective, if heat is leaving the system, the process is exothermic. Conversely, if heat is entering the system, the process is endothermic.

Conclude the qualitative changes: Based on the direction of heat flow, describe whether the system's temperature increases or decreases and whether the process is exothermic or endothermic.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Heat Transfer

Heat transfer refers to the movement of thermal energy from one object or system to another due to a temperature difference. In this scenario, heat can flow into or out of the container, affecting the temperature of both the system (contents of the container) and its surroundings (the water in the tub). Understanding how heat flows is crucial for predicting temperature changes.

Exothermic and Endothermic Processes

Exothermic processes release heat to the surroundings, resulting in an increase in the temperature of the surroundings and a decrease in the temperature of the system. Conversely, endothermic processes absorb heat from the surroundings, leading to a decrease in the temperature of the surroundings and an increase in the temperature of the system. Identifying whether the process is exothermic or endothermic is essential for understanding the thermal dynamics involved.

Thermal Equilibrium

Thermal equilibrium occurs when two systems in contact no longer exchange heat, resulting in both systems reaching the same temperature. In the context of the question, as heat flows between the container and the water, the system will eventually reach thermal equilibrium with its surroundings. This concept is important for predicting the final temperatures of both the system and the surroundings after the heat exchange.

Related Practice

Textbook Question

The diagram shows four states of a system, each with different internal energy, E. (c) Write an expression for the difference in energy between State C and State D.

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Textbook Question

Consider the two diagrams that follow. (d) Would similar relationships hold for the work involved in each process?

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Textbook Question

The diagram shows four states of a system, each with different internal energy, E. (a) Which of the states of the system has the greatest internal energy?

In the accompanying cylinder diagram, a chemical process occurs at constant temperature and pressure. (a) Is the sign of w indicated by this change positive or negative?

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