Latent Heat

Summary

• All phase changes…
  • take place at a specific temperature and for a given pressure.
  • take place without a change in temperature. (There is no temperature change during a phase change.)
  • involve changes in internal potential energy.
  • release or absorb latent heat.
    • Endothermic phase changes absorb heat from the environment. (They are cooling processes.)
    • Exothermic phase changes release heat to the environment. (They are warming processes.)
• The specific latent heat (L) of a material…
  • is a measure of the heat energy (Q) per mass (m) released or absorbed during a phase change.
  • is defined through the formula Q = mL.
  • is often just called the "latent heat" of the material.
  • uses the SI unit joule per kilogram [J/kg].
• There are three basic types of latent heat each associated with a different pair of phases.