Increasing the Melting Point via Pressure Increase

In summary, the pressure needed to increase the melting temperature by 20 centigrade degrees can be calculated using the Clapeyron relation. This is because an increase in pressure favors the denser solid phase, leading to an increase in melting temperature. The equation provided, delta H (s>l) = T(melting point)* delta S(s>l), can also be used if the molar or specific entropy of the solid and liquid are known. The latent heat energy is not necessary for solving this problem.
  • #1
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1. What is the pressure needed to increase the melting temperature by 20 centigrade degrees?

Given: Molar Volume (solid) at normal melting temp is 18.92 cm^3
Given: Molar Volume (liquid) at normal melting temp is 19.47 cm^3

Homework Equations



delta H (s>l) = T(melting point)* delta S(s>l)

The Attempt at a Solution



Not sure how I can even come up with an equation. I know I can calculate the change in volume with the molar volumes. The equation listed doesn't seem to help any either, anyone have an equation that works?

dP/dT = L/TdeltaV can't be used since I don't know latent heat...

Please help~
 
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  • #2
Look into the Clapeyron relation. An increase in pressure energetically favors the denser phase (solid) and therefore increases the melting temperature.
 
  • #3
Well I don't know the latent heat energy (it can be found, but the book is suggesting you can solve the problem without it, and without the actual melting point but simply knowing the change in melting point)
 
  • #4
The problem can also be solved if you know the molar or specific entropy of the solid and the liquid.
 

1. How does pressure affect the melting point of a substance?

Increasing pressure can raise the melting point of a substance because it compresses the atoms or molecules, making it more difficult for them to move and change from a solid to a liquid state.

2. Can any substance have its melting point increased by pressure?

No, not all substances' melting points can be increased by pressure. It depends on the type of bonding and the structure of the substance. Some substances, such as water, have a lower melting point under pressure due to the unique structure of their molecules.

3. How much pressure is needed to increase the melting point of a substance?

The amount of pressure needed to increase the melting point of a substance varies depending on the substance itself. Some substances may require very high pressures, while others may have their melting point increased with just a small increase in pressure.

4. What are some examples of substances that have a higher melting point under pressure?

Carbon dioxide (dry ice) is a common example of a substance with a higher melting point under pressure. Other examples include diamond, which has a melting point of over 3,800 degrees Celsius under normal atmospheric pressure but can melt at a lower temperature when subjected to high pressure.

5. Is increasing the melting point of a substance via pressure increase a reversible process?

Yes, increasing the melting point of a substance through pressure increase is a reversible process. When the pressure is released, the substance will return to its original melting point. However, some substances may undergo structural changes when subjected to high pressure, which can permanently alter their melting point.

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