Chemical and Physical Changes
Physical Change
● Changes in a substance that do not alter the chemical
properties of the substance
● Things about the substance change, but the substance
remains the same
● For instance, an ice cube melts into water and you can
boil that into a gas, but it remains H2O the whole time
● One or more of its physical properties may be changed
● Ex: change in size, shape, dissolving. possibly color
change (as long as a new substance is not created)
Chemical Change
● Changes that alter the chemical properties of
a substance
● A change that creates a different substance
● Clues: bubbles (indicates the production of a
gas), getting hot or cold, color change
● Ex: iron rusting, souring of milk, burning
paper
Observing Physical and Chemical Changes
Get out (or print) the worksheet titled
"Observing Chemical and Physical Changes."
Follow along with the slideshow as you fill in
the worksheet.
For each of the demonstrations:
1. Identify the substances as elements, compounds or
mixtures.
2. Write what you see occurring.
3. Identify the type of change.
1. Zinc turnings are placed in a
hydrochloric acid solution
1. Zinc turnings are placed in a
hydrochloric acid solution
● Zinc - Element
● HCl - compound
● Bubbles indicate a gas is being produced
● The Zinc seems to disappear which means
its being changed into a different substance
● Chemical Change
● What gas do you think is being produced?
2. Ripping Magnesium ribbon into
pieces then ignited in a flame
2. Ripping Magnesium ribbon into
pieces then ignited in a flame
● Magnesium - Element
● Burning is adding Oxygen gas
● Ripping the Magnesium is a physical
change, because we are changing the size
and shape, but not changing what the
substance is
● Burning is a chemical change because a
new substance is formed. The elements
Magnesium and Oxygen bond to form a
white powder- Magnesium Oxide
3. A penny is coated with zinc then
heated
Normal
Penny
Coated with
Zinc
After being
heated
3. A penny is coated with zinc then
heated
● Copper - Element
● Zinc - Element
● Coating the Copper with Zinc is a physical
change. Nothing new is created
● Heating dissolves the Zinc and Copper to
make brass. A solution of metals is called an
alloy. Alloys are considered a mixture of
metals and can be separated back, therefore
its not a chemical change.
4. Polymers A and B are mixed
4. Polymers A and B are mixed
● Polymer A and B are both compounds
● The reaction gives off heat (exothermic), a
new substance is created, therefore its a
chemical reaction
5. Hexane is poured down ramp and
ignited
5. Hexane down a ramp
● Hexane is a flammable liquid similar to
methane, propane, butane, octane (chemical
property)
● Hexane is a compound with a low boiling
point, so just exposing it to room
temperature turns it into a gas (similar to nail
polish remover)
● The hexane vapor is denser than air so it
sinks (physical property)
● When its ignited, it turns into a new
substance so that is a chemical change
6. A styrofoam cup in acetone
6. A styrofoam cup in acetone
● Acetone - compound
● Styrofoam - compound
● Bonds between the polymers of the
styrofoam are broken apart by the acetone
● The acetone is dissolving the styrofoam
● Its a physical change
7. Gas bubbles are made, then ignited
7. Gas bubbles are made
● The gas is methane, a compound
● Gas causes the bubble to expand - physical
change
● Gas bubble being ignited is a chemical
change
Congratulations!
● You have completed the notes on physical
and chemical changes.
● You do not have any other worksheet to
complete.