Physical changes alter an object's size, shape, or state but do not change its molecular structure. Chemical changes alter an object's molecular structure by forming new substances or releasing gases. Examples of physical changes include breaking a board in half and crumpling paper. Examples of chemical changes include rust forming on metal over time and paper burning and turning to ash.

1. Physical and Chemical changes
By: Patrick Kelly

2. Physical change
• A physical change is any change that occurs to
a substance that does not affect its molecular
structure.

3. A physical change occurs here as the
board is broken. The mass, size, and
shape of the board are changed as it
loses nearly half of its former self, but
the molecular structure of the wood
remains the same.

4. A physical change occurs here as the paper
is torn, then crumpled. The
mass, size, shape of the paper is changed
during the tear, and the shape is changed
as the paper is crumpled. However, niether
change affects the molecular structure of
the paper.

5. Chemical change
• A chemical change is any change to a
substance that changes its molecular
structure. A chemical change can usually be
seen by the formation of a new substance, the
releasing of a gas or odor, or an unexpected
color change.

6. A chemical change has occurred
here as the metal on this clamp
has rusted over time. As the
oxygen has reacted with the
metal, the new
substance, rust, has formed on top
of the metal. This alteration of the
chemical structure of both the
metal and the oxygen is a chemical
change.

7. A chemical change is occurring as the
paper is burning. The changing of the
paper into ash represents a chemical
change as it alters the molecular
structure of the paper. It also
releases smoke, which is a signal of a
chemical change.