How is the arrangement of molecules in a dense object different than arrangement by molecule in a less dense object

The molecules in a dense object are tightly packed together

Explanation:

This happens because the closer molecules are the denser the object is, however, if they get too close it can be a very disastrous result and the compound becomes very unstable. Hope I could help! :)

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.