Latent Heat (enthelpy) of Fusion changes with Pressure?

In summary, the melting point and latent heat of fusion may be affected by pressure. The equation for entropy of fusion to enthalpy of fusion is given by \Delta H=T\Delta S, where T is the temperature of melting. If the melting point increases with pressure, then the latent heat of fusion may decrease linearly during isentropic melting. However, typically melting is considered at fixed temperature, or isothermal melting. The isobaric thermal expansion coefficient can be used to integrate along the phase boundary T_\mathrm{melt}(p) for the two phases in equilibrium. The dependence of enthalpy before and after a phase change may also affect the latent heat.
  • #1
Hypatio
151
1
If the melting point depends on the pressure, does the latent heat of fusion also depend on the pressure? The equation relating the entropy of fusion to the enthalpy of fusion is given by:

[tex]\Delta H=T\Delta S[/tex]

where T is, apparently, the temperature of melting. So, if the melting point increases with pressure, then as isentropic melting occurs the latent heat (enthalpy) of fusion decreases linearly?
 
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  • #2
Hypatio said:
If the melting point depends on the pressure, does the latent heat of fusion also depend on the pressure? The equation relating the entropy of fusion to the enthalpy of fusion is given by:

[itex]\Delta H=T\Delta S[/itex]

where T is, apparently, the temperature of melting. So, if the melting point increases with pressure, then as isentropic melting occurs the latent heat (enthalpy) of fusion decreases linearly?

What do you mean with isentropic melting? Usually one considers melting at fixed temperature, i.e. isothermal melting.

Generally
[itex]
dH=C_p dT +(V-T \frac{\partial V}{\partial T}|_p}dp
[/itex]
with the last term in the brackets defines the isobaric thermal expansion coefficient.
Just integrate along the phase boundary [itex]T_\mathrm{melt}(p)[/itex] for the two phases in equilibrium.
 
  • #3
Hello Sir,
Latent heat of anything can simply be calculated by taking the difference between enthalpy after and before.

I dont' remember but the dependence of the enthalpy before and after will tell you if it will change the latent heat.
 

1. What is Latent Heat of Fusion?

Latent Heat of Fusion is the amount of energy required to change a substance from a solid phase to a liquid phase at constant temperature and pressure.

2. How does Latent Heat of Fusion change with pressure?

As pressure increases, the molecules in a substance are forced closer together, making it more difficult for them to transition from a solid to a liquid state. This leads to an increase in the Latent Heat of Fusion.

3. Why does Latent Heat of Fusion change with pressure?

The change in Latent Heat of Fusion with pressure is due to the effect of pressure on the intermolecular forces between molecules in a substance. As pressure increases, these forces become stronger, requiring more energy to overcome them and cause a phase change.

4. How is Latent Heat of Fusion measured?

Latent Heat of Fusion is typically measured in joules per kilogram (J/kg) or calories per gram (cal/g). It can also be calculated by dividing the amount of energy needed to change a certain mass of substance from solid to liquid by the mass itself.

5. Does Latent Heat of Fusion change for all substances with pressure?

No, the change in Latent Heat of Fusion with pressure depends on the specific substance and its intermolecular forces. Some substances may have a decrease in Latent Heat of Fusion with pressure, while others may have an increase.

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