Answer these questions Please !

[zain942010]

(a) explain using a simple kinetic model for matter why

• melting and boiling take place without a change in
temperature

• the specific latent heat of vaporisation is higher than specific
latent heat of fusion for the same substance

 

[no.mercy]

a) During melting and boiling, the energy is being absorbed to break the bonds so therefore there is no increase in temperature.
b) i dunno..

 

[Khan_971]

(a) explain using a simple kinetic model for matter why

• melting and boiling take place without a change in
temperature

• the specific latent heat of vaporisation is higher than specific
latent heat of fusion for the same substance

Melting and boiling involves Increase in potential energy (breaking bonds) of the molecules/atoms of the matter. The Kinetic energy is unaffected an will be as per the temperature. (Meaning the energy supplied is absorbed to increase Potential energy of the matter, breaking bonds)

As for the 2nd, Read carefully through this:
Quoted:

Now as you heat a solid turning it into a liquid, you increase the kinetic energy of its molecules, moving them further apart until the forces of attraction are reduced to allow it to flow freely. Keep in mind the forces of attraction still exists. Now as you heat a liquid, turning it into a gas, the kinetic energy of the molecules are increased to a point where there are no forces of attraction between the molecules.

http://www.physlink.com/education/askexperts/ae93.cfm I found the answer here

 

[MindStealth]

• Melting and boiling involves breaking of bonds and that is done by overcoming the forces of the bonds. During both of these processes, all the energy supplied is used to over come the forces by increasing the separation between the atoms, thus increasing their potential energy. Since all the energy is used to increase the potential energy, there is no change in the kinetic energy and temperature is actually the measure of the average kinetic energy so it stays constant.
• To answer this you have to compare the process of melting and boiling. In melting, the solid changes to liquid. The atoms in the solid are very tightly held, and in the liquid phase they're just lose enough so they can move about each other, this separation is much less than that required to change a liquid into a gas. The atoms in a liquid is not as tight as a solid but compared to a gas, they're still tight enough, they only move about each other but during the process of boiling, the separation is increased so much that the forces between them are negligible. The energy required to completely separate the molecules, moving from liquid to gas, is much greater than if you were just to increase their separation a little, solid to liquid. Hence the reason why the latent heat of vaporization is greater that the latent heat of fusion.

This is a common misconception about phases that liquid comes in the middle of solid and gas state; in reality, the liquid state is much closer to the solid state than gaseous state.