CHANGES IN MATTER
and ATOMS & MOLECULES...

Matter can undergo three changes...

1) chemical = change in composition and (perhaps) a change in physical state; molecules recombine to form new ones; examples include the cooking of foods, corrosion; fermentation; souring milk


2) physical = no change in the composition of the
substance and only a change in physical state takes
place; melting of a solid like glass; freezing of a liquid
like water; formation of snow from water vapor ;
the molecular particles remain unchanged; energy
may be absorbed or given off during a physical change


3) nuclear = change in the nuclei of atoms;
nuclear fusion in the sun where light atoms of
hydrogen join to form heavier atoms of Helium;
large energy changes occur; nuclear fission involves
striking an atom's nuclei with a neutron splitting it into
smaller fragments and the evolving heat energy is
is converted into electricity; nuclear changes result
in the changing of an atom of one element into an
atom of another