Chemical changes occur when asubstance combines with another to form a new substance, called chemicalsynthesis or, alternatively, chemicaldecomposition into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions.
Because lager objects have much more room for mass the smaller objects. take the earth as an example the earth is very big and has alot of mass in it which makes gravity that pulls us down when we jump up.
