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Chapter 5: Problem 24

(a) Write an equation that expresses the first law of thermodynamics in terms of heat and work. (b) Under what conditions will the quantities \(q\) and \(w\) be negative numbers?

Short Answer

Expert verified
(a) The First Law of Thermodynamics equation is: ΔU = q + w (b) The conditions for negative values of \(q\) and \(w\) are: - \(q\) is negative when heat is removed from the system. - \(w\) is negative when work is done on the system.

Step by step solution

01

(a) Formulate the First Law of Thermodynamics equation

The First Law of Thermodynamics equation is given by: ΔU = q + w where ΔU represents the change in internal energy, q represents the heat added to the system, and w represents the work done by the system.
02

(b) Identify conditions for negative q and w values

Let's analyze the conditions that make the heat (\(q\)) and work (\(w\)) quantities negative. 1. Negative heat (q < 0): Heat is considered negative when it's being removed from the system. This is because heat leaving the system causes the internal energy of the system to decrease. 2. Negative work (w < 0): Work is considered negative when the work is done on the system. This is because when work is performed on the system, the internal energy of the system increases as a consequence of an external force acting on it. So, - \(q\) will be negative when heat is removed from the system. - \(w\) will be negative when work is done on the system.

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