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 23b

Chapter 5, Problem 23b

(b) What is meant by the internal energy of a system?

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The internal energy of a system, often denoted as 'U', is the total energy contained within the system. It includes all forms of energy such as kinetic energy due to the motion of particles and potential energy due to the interactions between particles.

Internal energy is a state function, meaning it depends only on the current state of the system and not on how the system reached that state. This implies that changes in internal energy are independent of the path taken.

In thermodynamics, the change in internal energy (ΔU) of a system can be expressed using the first law of thermodynamics: ΔU = Q - W, where Q is the heat added to the system and W is the work done by the system.

The internal energy can be influenced by changes in temperature, volume, and pressure, as these factors affect the kinetic and potential energies of the particles within the system.

Understanding internal energy is crucial for analyzing energy changes in chemical reactions and physical processes, as it helps in determining how energy is transferred and transformed within a system.

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Key Concepts

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

Internal Energy

Internal energy is the total energy contained within a thermodynamic system, encompassing both kinetic and potential energy at the molecular level. It reflects the energy associated with the motion of particles and the interactions between them. Changes in internal energy can occur due to heat transfer or work done on or by the system.

First Law of Thermodynamics

The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This principle implies that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. It establishes a fundamental relationship between internal energy, heat, and work.

State Functions

State functions are properties of a system that depend only on its current state, not on the path taken to reach that state. Internal energy is a state function, meaning its value is determined solely by the current conditions of the system, such as temperature and pressure. This characteristic allows for easier calculations and predictions in thermodynamics.

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Related Practice

Textbook Question

(a) According to the first law of thermodynamics, what quantity is conserved?

In a thermodynamic study, a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (b) If the inlet and outlet were closed, what type of system would it be

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Textbook Question

Calculate ΔE and determine whether the process is endothermic or exothermic for the following cases: (a) q = 0.763 kJ and w = -840 J.

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