Question

Explain why

A) Why the latent heat of vaporization is larger (usually much larger) than the latent heat of fusion for any process.

B) Heat flows from high to low temperatures.

Answer 1

A)

Latent heat of vaporization is the amount of heat required to change the state of a substance from liquid to gas or vice versa where as latent heat of fusion is the amount of heat required to change the state of a substance from solid to liquid or vice versa.

Now when we are converting a solid to liquid, we are just giving the molecules enough enough energy so as to increase their distance, which is the case of molcules of liquid. This energy as mentioned already is the latent heat of fusion. While converting a liquid to gas though, we have to give energy such the molecules of liquid which is closely packed are sepated. Hence this requires larger energy than the latent heat of fusion. This energy is the latent heat of vaporization.

Hence the latent hear of vaporization is greater than the latent heat of fusion.

B)

This can be simply answered based on conservation of energy, which states without external energy, total energy of a sytem is constant.

Now a body which has higher temparatures has more energy than the body with lower temparatures. When the energy starts transferring, since the energy is conserved, the hot body's energy is tranferred to the cold bdy not vice versa.

Hence heat flows from high to low temparatures.