Question

the graph shows that the substance takes longer to boil that to melt give a reason for this?

Answer 1

It takes longer to boil water than to melt ice because of the difference in the amount of heat required to overcome the forces of attraction by keeping the temperature constant during this time. When ice is melting it is called latent heat of fusion which needs around 334 joules per gram and whereas when the water is boiling it is called latent heat of vaporization which needs around 2230 joules of energy.

Taking this information in hand we can see that that boiling needs approximately 6 to 7 times more amount of energy than in melting. This is the reason it takes longer in boiling than in melting.