The middle carbon is 4-degree since it is attached to 4 carbons. All other carbons are 1-degree since they are attached to only 1 carbon.
Hydrogens attached with 1-degree carbon are all same. Hydrogen are often refereed to as protons. No carbon is attached to 4-degree carbon. So all hydrogens in this structure are same.
The law of conservation of mass states that the quantity of the mass can neither be added to, neither can it be removed. The greater picture's mass will always be the same amount.