Boiling Water at High Pressure. When water is boiled at a...

Boiling Water at High Pressure. When water is boiled at a pressure of $2.00 \mathrm{atm},$ the heat of vaporization is $2.20 \times 10^{5} \mathrm{J} / \mathrm{kg}$ and the boiling point is $120^{\circ} \mathrm{C}$ . At this pressure, 1.00 $\mathrm{kg}$ of water has a volume of $1.00 \times 10^{-3} \mathrm{m}^{3}$ , and 1.00 $\mathrm{kg}$ of steam has a volume of $0.824 \mathrm{m}^{3} .$ (a) Compute the work done when 1.00 $\mathrm{kg}$ of steam is formed at this temperature. (b) Compute the increase in internal energy of the water.

Key Concepts

Work in Thermodynamic Processes

Work in a thermodynamic context is the energy transferred when a system undergoes a volume change under pressure. When a substance like water vaporizes, its volume increases dramatically and, if the process occurs at constant pressure, the work done by the system can be calculated using the product of the pressure and the change in volume. This principle is fundamental in analyzing energy exchanges during expansion or compression in various thermodynamic processes.

Phase Change and Latent Heat

Phase change refers to the transition of a substance from one state of matter to another, such as from liquid to gas, without a change in temperature. Latent heat is the energy absorbed or released during this transition, which allows the substance to overcome intermolecular forces rather than increasing kinetic energy. This concept is central to understanding how energy is managed during boiling and condensation processes.

First Law of Thermodynamics

The First Law of Thermodynamics is a statement of energy conservation, asserting that the change in a system’s internal energy is equal to the heat supplied to the system minus the work done by the system on its surroundings. This law provides a framework for understanding how energy is distributed during processes such as boiling, where energy is used both to change the phase of the substance and to perform work against external pressure.

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