The above reaction is least energetic because there is no phosphoanhydride bond present with adenosine mono phosphate.Phospho anhydride bond is an energy rich bond.
As a result hydrolysis of AMP generates very little amount of energy in comparison to the hydrolysis of ATP and ADP.
Answer: In order to melt a network solid, a relatively large amount of heat is needed, sufficient to break the covalent bonds that hold the entire solid together
