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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.
- 14.3 Phase Change and Latent Heat - College Physics 2e - OpenStax
Latent heat is measured in units of J/kg. Both L f and L v...
- 14.3 Phase Change and Latent Heat - College Physics 2e - OpenStax
• 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 needed to change the temperature of a given substance (with no change in phase) is: q = m × c × ΔT (see previous chapter on thermochemistry). The heat needed to induce a given change in phase is given by q = n × ΔH. Using these equations with the appropriate values for specific heat of ice, water, and steam, and enthalpies of ...
Phase changes occur at fixed temperatures for a given substance at a given pressure, and these temperatures are called boiling and freezing (or melting) points. During phase changes, heat absorbed or released is given by: \[Q=m L, \nonumber\] where \(L\) is the latent heat coefficient.
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.
24 Σεπ 2022 · According to our discussion of phase changes, the heat needed to effect these two phase changes are \(\Delta_\text{fus} H\) and \(\Delta_\text{vap} H\), respectively. At these temperatures, \(C_P = \partial H/\partial T\) diverges, and we cannot smoothly integrate through these divergences.
Latent heat is measured in units of J/kg. Both L f and L v depend on the substance, particularly on the strength of its molecular forces as noted earlier. L f and L v are collectively called latent heat coefficients.
