DEMOS
• Write down your observations during
the DEMOS your teacher does on your
Lab Sheet under EVIDENCE of a change.
• Determine if you believe the DEMO
shows a CHEMICAL or PHYSICAL change
or BOTH.
DEMO
• What happens when you mix sulfuric acid and
table sugar?
The Difference
• Physical Change – matter changes form
but is still made of the same molecules,
typically reversible
• Chemical Change – a change in the
molecules occurs, cannot be reversed
How can you tell which change it is?
• Chemical Change - Substance changes into
something new. You can tell because of color
change, heat or light given off or taken in,
precipitate, gas bubbles; new substances form.
• Physical Change - Substance doesn’t change to
something new, it may change form, shape, size or
phase but it is still the same stuff. It is reversible
and sometimes requires heat from the outside to
make it happen but does not release heat by
itself.
Physical Changes
• Physical Change – matter changes form but is
still made of the same molecules, typically
reversible
Example:
An ice cube melting
Solid H2O  Liquid H2O
Both the beginning and ending products are made
of H2O, the molecules stayed the same
Physical Changes
• Physical Change – matter changes form but is
still made of the same molecules, typically
reversible
Example:
A bag of potatoes is
squished up to make
mashed potatoes
Physical Changes
EXAMPLE:
The digestive system is very muscular and
causes physical changes starting with chewing
and continuing with churning in the stomach
Chemical Changes
EXAMPLE:
The digestive system also causes chemical
changes by using enzymes and chemicals to
break the food down into its components
Evidence of a Physical Change
• There are three signs that a physical change
has occurred (remember, this means that your
starting and ending molecules are the same)
1. Change in Size
2. Change in Shape
3. Change in Phase of Matter
Evidence of a Chemical Change
• There are five signs that a chemical change has
occurred (remember, this means that your starting and
ending molecules are different)
1.
2.
3.
4.
5.
Change in Temperature
Change in Color
Change or Creation of Odor
Formation of a Precipitate (a solid material)
Formation of a Gas
Chemical or Physical Change?
Physical!
Chemical or Physical Change?
Chemical!
Chemical or Physical Change?
Physical!
Chemical or Physical Change?
Chemical!
Chemical or Physical Change?
Chemical!
Chemical or Physical Change?
Physical!
Chemical or Physical Change?
Chemical!