Explanation:
The bonds that keep molecules together break apart and form new bonds during chemical reactions, rearranging atoms into different substances. Each bond takes a distinct amount of energy to either break or form; the reaction does not take place without this energy, and the reactants stay as they were.
-- Volume . . . made out of 3 dimensions of length
-- Density . . . made out of mass, and 3 dimensions of length
-- Area . . . made out of 2 dimensions of length
-- Acceleration . . . made out of length and time
<em>Mass</em> is not made out of anything else. It's fundamental. A few other fundamental things are length, time, and electric charge.
