Why does the plot show vertical jumps at the melting and boiling points?

I think this happens because during melting or boiling at constant temperature, the entropy dramatically increases because energy is removed from the system during the change. Entropy increases with increase in temperature, entropy increases steadily with increasing temperature up to the melting point of the solid, where the entropy increases further due to addition of freedom of molecules which increases the randomness of the substance. At boiling point of liquid, another abrupt increase in entropy occurs, this results from increased volume available to the atoms or molecules as they enter the gaseous state. 

Answer

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

explanation

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

The rearrangement of particles in a physical change. hope this