Heat of Fusion

Heat of Fusion

Specific heat capacity is the heat needed to raise the temperature of one gram (g) of a substance by one degree Celsius. Specific heat capacity plays a role in the amount of heat absorbed or released by a substance because when there is high specific heat it takes a lot of energy to raise its temperature but when there is, low specific heat it does not take a lot of energy to raise its temperature. On the other hand, latent heat is energy that is absorbed or released each time water has a change in state. This energy is latent heat. Latent heat is the energy absorbed or released when a substance changes its physical state. Latent heat is absorbed immediately after evaporation, and released in the state change of condensation to liquid (ex: clouds). Latent heat is also absorbed when water melts, and released when it freezes. Latent heat is different from energy absorbed or released during temperature change because there is no temperature change during a phase change; therefore, there is no change in the kinetic energy of the particles in the material. The energy released comes from the potential energy stored in the bonds between the particles.

Aluminum vs. Water

Specific Heat Capacity (q = mCp T) Heat of Fusion (Q = mHf) Heat of Vaporization (Q = mHv)

Aluminum 0.89 J/g 10.79kJ/mol 293.4kJ/mol

Water 4.184 J/g°C

334 J/g 2260 J/g

As you can see in the table above, aluminum has a lower specific heat compared to water which has a higher specific heat. This is because since aluminum has a low specific heat it can heat up quicker and cool down quicker. However, since water has a higher specific it takes longer to heat up and cool down.

Heating Curve: Aluminum

• Line AB = KE increases, Temperature increase, Solid ONLY.

• Line BC = Melting (solid to liquid), PE increases, KE remains the SAME.

• Line CD = KE increases, Temperature increases, Liquid ONLY.

• Line DE = Boling (liquid to gas), PE increases, KE remains the SAME, Temperature remains the SAME.

• Line EF = KE increases, Temperature increases, Gas ONLY.

<Melting Point <Vaporizing