List two types of isotopes occurring in nature.
51. Three types of changes take place in matter-physical, chemical, and nuclear.
A physical change is a change of state, and the composition of the
substance is not altered. The change from water to ice is a physical change,
as there is no change in the arrangement of the atoms. Chemical changes
are characterized by a rearrangement of the electron structure, which
produces a new substance. The combination of iron and oxygen to form the
new substance, iron oxide (rust), is an example of a chemical change. When
a nuclear change occurs, atoms of one element are changed to atoms of
another element. The gradual change of radium atoms to lead atoms is a
The three types of changes that take place in matter are physical,
__________________, and ____________________ .