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Explain the construction and use of a typical phase diagram. Use phase diagrams to identify stable phases at given temperatures and pressures, and to describe phase transitions resulting from changes in these properties. Describe the supercritical fluid phase of matter.
- Problems
On the phase diagram, label the gas and liquid regions....
- 8.7.7: Phase Change and Latent Heat
\(L_{\mathrm{f}}\) and \(L_{\mathrm{v}}\) are collectively...
- 13.3: Phase Change and Latent Heat
The heat Q required to change the phase of a sample of mass...
- Problems
The energy changes that occur during phase changes can be quantified by using a heating or cooling curve. Heating Curves Figure \(\PageIndex{3}\) shows a heating curve, a plot of temperature versus heating time, for a 75 g sample of water.
The latent heat of fusion is the amount of heat needed to cause a phase change between solid and liquid. The latent heat of vaporization is the amount of heat needed to cause a phase change between liquid and gas.
\(L_{\mathrm{f}}\) and \(L_{\mathrm{v}}\) are collectively called latent heat coefficients. They are latent, or hidden, because in phase changes, energy enters or leaves a system without causing a temperature change in the system; so, in effect, the energy is hidden.
Melting a solid requires an input of energy (at constant temperature) to loosen up the molecular or atomic bonds. Vaporizing a liquid involves an input of energy to increase the separation between molecules. Here, the latent heat involves a change in internal energy, plus work in expanding the volume.
The heat Q required to change the phase of a sample of mass m is given by \(\mathrm{Q=mL_f}\) (melting or freezing) and \(\mathrm{Q=mL_v}\) (evaporating or condensing), where \(\mathrm{L_f}\) and \(\mathrm{L_v}\) are the latent heat of fusion and the latent heat of vaporization, respectively.
Latent heat is energy transferred in a process without change of the body's temperature, for example, in a phase change (solid/liquid/gas). Both sensible and latent heats are observed in many processes of transfer of energy in nature.
