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Q = m L f (for melting/freezing), Q = m L v (for vaporization/condensation), where L f is the latent heat of fusion, and L v is the latent heat of vaporization. The latent heat of fusion is the amount of heat needed to cause a phase change between solid and liquid.
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.
• 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. Examples of latent heats: material fusion, L f (J / kg) vaporization, L v (J / kg) water 33.5 x 104 22.6 x 105 ethyl alcohol 10.8 x 104 8.55 x 105
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.
\(L_{\mathrm{f}}\) 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.
23 Ιουλ 2024 · This curve effectively illustrates how temperature remains constant during phase changes, such as melting and boiling, due to the absorption of latent heat, which is crucial for understanding latent heat and enthalpy in phase transitions.
If heat were added at a constant rate to a mass of ice to take it through its phase changes to liquid water and then to steam, the energies required to accomplish the phase changes (called the latent heat of fusion and latent heat of vaporization) would lead to plateaus in the temperature vs time graph.
