Latent Heat of Fusion
Heat energy required to change unit mass of a substance from solid to liquid state at its melting point without change in its temperature is called its latent heat of fusion.
When a substance is changed from solid to liquid state by adding heat, the process is called melting or fusion. The temperature at which a solid starts melting is called its fusion point or melting point.When a process is reversed i.e., when a liquid is cooled, it changes into solid state. The temperature at which a substance changes from liquid to solid state is called its freezing point. Different substances have different melting points. However, the freezing point of a substance is the same as its melting point.
It is denoted by Hf.
Hf = ΔQf/ m
or Δ Qf = m Hf … …. … … (4)
Latent heat of fusion of ice
Ice changes at 0° C into water. Latent heat of fusion of ice is 3.36 × 105 J kg -1. That is; 3.36 × 105 Joule heat is required to melt 1 kg of ice into water at 0°C.