On a temperature versus time graph, how does the temperature at the beginning of a change is state compare with the temperature at the end of the change

The temperature will remain the same.

Explanation:

When a material goes through a change of state, the temperature remains the same as witnessed on a temperature versus the time graph. Each change of state, that is, condensation, evaporation, melting, and fusion needs the withdrawal or supplementation of energy called latent heat. At the point of a change of state, there is no change in temperature. Though, in between the changes of states, the modifications in temperatures are brought about by the sensible heat.

the dissolution of polymer can be thermodynamically described in 2 steps.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.