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Ch. 20 - Second Law of Thermodynamics
Giancoli Douglas - Physics for Scientists and Engineers 5th edition
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoGiancoli Douglas 5th editionCh. 20 - Second Law of ThermodynamicsProblema 38b
Capitolo 20, Problema 38b

If 0.45 kg of water at 100°C is changed by a reversible process to steam at 100°C, determine the change in entropy of the surroundings.

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Identify the key concept: The change in entropy of the surroundings is related to the heat exchanged with the surroundings and the temperature at which the exchange occurs. The formula for entropy change is ΔS = -Q/T, where Q is the heat exchanged and T is the absolute temperature.
Determine the heat exchanged (Q): The heat required to convert water to steam at 100°C is given by Q = mL, where m is the mass of the water (0.45 kg) and L is the latent heat of vaporization of water (L = 2.26 × 10^6 J/kg).
Substitute the values into the formula for Q: Q = (0.45 kg) × (2.26 × 10^6 J/kg). This gives the total heat exchanged during the phase change.
Calculate the temperature in absolute terms: Since the process occurs at 100°C, convert this to Kelvin using T(K) = T(°C) + 273.15. Thus, T = 100 + 273.15 = 373.15 K.
Substitute Q and T into the entropy formula: ΔS_surroundings = -Q/T. Use the value of Q from step 3 and T from step 4 to express the change in entropy of the surroundings.

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Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the amount of energy in a system that is not available to do work. When a substance undergoes a phase change, such as from water to steam, the entropy of the system changes, reflecting the increased disorder as molecules move from a liquid to a gaseous state.
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Reversible Process

A reversible process is an idealized process that occurs in such a way that the system and surroundings can be returned to their original states without any net change. In thermodynamics, reversible processes are characterized by equilibrium at every stage, allowing for maximum efficiency and the ability to calculate changes in properties like entropy accurately.
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Surroundings

In thermodynamics, the surroundings refer to everything outside the system being studied. When analyzing changes in a system, such as the transition of water to steam, it is essential to consider the heat exchange with the surroundings, as this affects the overall entropy change. The surroundings can absorb or release heat, influencing the entropy of both the system and the environment.
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