Specific Latent Heat

Specific Latent Heat

Basic Definitions

  • Specific latent heat is the energy required to change the state of a 1 kg substance without changing its temperature.
  • The term ‘latent’ means hidden, implying energy put into or taken from a substance during a change of state doesn’t cause a temperature change.
  • There are two types of specific latent heat: specific latent heat of fusion and specific latent heat of vaporisation.

Specific Latent Heat of Fusion

  • Specific latent heat of fusion (L_f) refers to the energy needed to change a substance from solid to liquid at its melting point.
  • For example, ice at 0 degrees Celsius needs to absorb a certain amount of energy to melt into water at 0 degrees Celsius.

Specific Latent Heat of Vaporisation

  • Specific latent heat of vaporisation (L_v) is the energy required to change a substance from liquid to gas at its boiling point.
  • For instance, water at 100 degrees Celsius needs to absorb a certain quantity of energy to become steam at the same temperature.

Calculating Energy Involving Specific Latent Heat

  • The energy (E) involved in a change of state can be calculated using the formula: E = m × L, where ‘m’ is the mass and ‘L’ is the specific latent heat.
  • Depending on the context, ‘L’ could represent L_f or L_v.

Real World Applications

  • Understanding specific latent heat is crucial for many everyday applications such as refrigeration and heating systems.

Common Misconceptions

  • A common confusion is thinking that temperature must change during a change of state. Remember that during a change of state, energy is used to break or form bonds between particles, not to raise the temperature.