Respuesta :
Energy is required to change the phase of a substance, such as the energy to break the bonds between molecules in a block of ice so it may melt.
During a phase change energy my be added or subtracted from a system, but the temperature will not change. The temperature will change only when the phase change has completed.
The heat Q required to change the phase of a sample of mass m is given by
Q
=
mL
f
(melting or freezing) and
Q
=
mL
v
(evaporating or condensing), where Lf and Lv are the latent heat of fusion and the latent heat of vaporization, respectively.
Key Terms
latent heat of fusion: the energy required to transition one unit of a substance from solid to liquid; equivalently, the energy liberated when one unit of a substance transitions from liquid to solid.
latent heat of vaporization: the energy required to transition one unit of a substance from liquid to vapor; equivalently, the energy liberated when one unit of a substance transitions from vapor to liquid.
sublimation: the transition of a substance from the solid phase directly to the vapor state such that it does not pass through the intermediate, liquid phase
