Science Focus Lesson
Physical and
Chemical Changes
Duval County Public Schools
Essential Question:
How can scientists differentiate
between a physical and chemical
change?
Vocabulary:
Physical
Chemical
solution
evaporate
mixture
dissolve
melt
•Matter has mass and takes up
space
•Solid, liquid, gas are the three
different states
•Matter has properties that tell what
it’s like
•It goes through physical and
chemical changes, that’s right!
Physical Properties
Think Five Senses…
 Color
 Smell
 Taste
 Volume
 Mass
 Solubility
 State or Phase
 Boiling, freezing and melting point
Physical Change
 Physical changes occur when matter
changes its physical property but not
its chemical nature.
 Physical property changes could
include changes in: texture, shape, size,
color, odor, volume, mass, weight, and
density.
 These changes can be reversed!
Physical Change
The shape and volume was changed but the chemical
make-up remains the same. It’s still H20!
Physical Change
The shape was change but the mass remains the same!
Physical Change
The shape and state was changed but the
mass and volume remains the same! Ah, but
how can I reverse it?
Summarizing
Think…Pair…Share
In a physical change, the object stays the
same A to Partner B: Name an example of a
Partner
You
can fold
it, bend it, cut it, but the object
physical
change
still
remains
Partner B to Partner A: Explain why that
Aexample
physicalischange
doesn’t
really change
a physical
change?
the matter
Both partners: Find this part of the Matter
The matter just moves from one state to
Song in your IAN’s!
another…
Chemical Properties
Think Five Senses…
 Indicates how a
substance reacts
with something
else.
 The original
substance is
changed into a
different substance.
Chemical Change
 Chemical changes are changes matter
undergoes when it becomes new or
different matter.
 These changes Cannot be reversed!
Signs of a Chemical Change
•Evidence of a chemical reaction
•Formation of gas – bubbles!
•Formation of a new substance -- rust
•Change in color -- leaves
•Gives off Light – glow stick
•Change in thermal energy
•Endothermic Absorbs heat
energy (gets cold) – cold pack
•Exothermic Releases heat energy
(gets hot) – hand warmer
Chemical Change
Each of the original ingredients now have different
physical and chemical properties than the final product
does!
Chemical Change
The original material now has different physical and
chemical properties than the final product does!
Chemical Change
The original substance now has different physical and
chemical properties than the final product does!
Summarizing
The most important thing
Pair
In aShare:
chemical change, a new substance is
Partner A tell B what the most important thing
created
is that
learned
from
this lesson…why?
You
canyou
rust
it, burn
it, cook
it, but you can’t
Partner
reverseBittell A what the most important thing
you learned
fromsomething
this lesson…why?
Inisathat
chemical
change
new will
Both
formpartners, find this part of the Matter Song!
Energy is given off or energy is absorbed!
Physical Change
Chemical Change
Temperature and Change!
 What will happen to a substance if heat is added to it?
What would happen if the temperature is decreased?
 http://youtu.be/j6KGXZ3m6ys
Guided Instruction:
1. Claire adds 10 grams (g) of salt to a jar of cold water. She then
adds 10 g of salt to a second jar of hot water. She covers and shakes
both jars and sets them on the table for five minutes. The materials
Dani used are shown below. What should Dani expect to observe
after those five minutes?
a. In both jars, the salt dissolved at the same rate.
b. The salt in the jar with hot water dissolved slower.
c. The salt in the jar with the cold water dissolved slower.
d. The salt remained at the bottom of both jars in equal amounts.
The answer is
When matter dissolves in water with more
heat energy, it forms a solution faster. Salt
will form a salt water solution when mixed
with water, sand does not dissolve in
water and will sink to the bottom.
Guided Instruction:
2. Markell wants to do an investigation to see how heat affects a
physical change in a substance. Which of the following is an
investigation he can conduct?
a. Add heat to a marshmallow to see how long it takes to burn.
b. Remove heat from water to see how long it takes for sugar to
dissolve.
c. Add heat energy to different sizes of paper to see if larger
pieces take long to burn than smaller ones.
d. Test batteries from the freezer against batteries from a hot car
to see which last longest in a flashlight.
The answer is
Dissolving sugar in water is a physical
change. The sugar can be reclaimed by
evaporating the water. All of the other
choices are chemical changes because
the substances are changed irreversibly.
Guided Instruction:
3. Laila left her balloon in the car on a hot day. When she came back
to the car, the balloon had popped. What most likely happened to the
balloon?
a. The air molecules inside the balloon combined to form a solid.
b. The balloon got smaller and squeezed out the air.
c. The air inside the balloon heated up and expanded
d. The air inside the balloon condensed into a liquid.
The answer is
Most matter expands when thermal
energy is added to it. Her balloons were
filled with helium that expanded as the
temperature went up. At some point, the
balloons popped because the gas
expanded as it warmed. Remember the
bubble experiment?
Summarizing
Talking Chips
One at a time, each team mate tell the others
what science finding surprises you the most!
Check Your Understanding
1.
Builders leave gaps, or spaces, between the parts of a metal
bridge. They do this so the bridge can change when it gets hot.
Based on this, what most likely happens to metal when it is
heated?
A.)
B.)
C.)
D.)
Most metals expand when they are heated.
Most metals contract when they are heated.
Most metals change into other substances when they are heated.
Most metals crack when they are heated.
Check Your Understanding
2.
One way weathering happens is when water gets inside the cracks
of rocks and boulders in colder regions. What most likely causes
this to happen?
A.) Most rocks have water in them, and it wears the rocks down.
B.) As the water gets in the cracks, it expands as it heats up.
C.) As water freezes, it contracts in the cracks and pulls the cracks
wider.
D.) As water freezes, it expands in the cracks and pushes the cracks
wider..
Check Your Understanding
3)
Raina was investigating physical and chemical changes for her
science fair project. She was mixing different chemicals together
and observing their reactions. Which of the following is a common
sign that a chemical change has occurred?
A.) A chemical has changed size.
B.) A chemical has turned a different color.
C.) A chemical has become a different shape.
D.) A chemical has changed to a different state (solid, liquid or
gas)
Check Your Understanding
4.
Teron draws a picture on a piece of paper and then folds it into a
paper airplane. He throws it at King, and its hits him in the head. He
responds by ripping up the paper. Which of the following is an
example of a physical change?
A.) ripping up the paper
B.) folding the paper into an airplane
C.) drawing on the paper
D.) all of these
Check Your Answers
1. A. Most matter expands as it heats, but not
water, it expands as it freezes.
2. D. As water freezes, it expands in the cracks
and pushes the cracks wider.
3. B. A chemical has turned a different color.
4. D. all of these
Summary Question
Quick Write:
How can scientists identify and physical
and chemical change?