Physical vs. Chemical Changes
Warm-up
6 March 2013
From the “Cooking with Chemistry” activity,
describe how did you use phase change to
complete the final task of separating the
salt from the solution?
http://whatscookingamerica.net/Foto4/BoilingWater.bmp
Review of Previous Knowledge
3/6/2013
______ 1. Aluminum can be flattened into sheets of foil.
______ 2. Water is frozen into ice.
______ 3. Copper can be pulled into thin wires.
______ 4. Your hand grows warm from holding a cup of
hot liquid.
______ 5. Flavored drink mix dissolves in water.
______ 6. An onion gives off a very distinctive smell.
______ 7. A golf ball has more mass than a table tennis
ball.
-L
State
solubility
thermal conductivity
Malleability
odor
ductility
density
Physical Property:
Chemical Property:
Example:
Example:
Physical Change:
Chemical Change:
Example:
Example:
Signs of a physical change:
Signs of a chemical change:
What’s the Difference?



Matter can change
Examples: Freeze, cut, burn, etc.
2 types of changes
1.
2.
Physical changes
Chemical changes
Physical Property
 Characteristic
of matter
that does not change the
substance (using senses)
Physical Changes

Matter changes form WITHOUT becoming
something new
–

You start and end with same thing (see below)
Examples: cutting, freezing, melting, etc.
Molecules in Physical Changes
Chemical Property
 Describes
matter on its ability
to change into new matter
– Flammability:
ability of substance
to burn
– Reactivity: ability of substance to
change into new substance
Chemical Changes

Matter changes, becomes NEW substance
–


Start and end with different things
Usually irreversible (can’t change back)
Examples: burning, rusting, milk going sour
Signs of Change

Physical
–
–
–
Size
Shape
Texture

Chemical
–
–
–
–
–
Temperature
Color
Bubbles/fizzing
Smoke
Smell
Chemical Change = _________________
In chemical changes, atoms and molecules rearrange to form new substances.
Reactants:
Products:
Molecules in Chemical Changes

The atoms
arrange to make
a new substance
Mixing Things Up: Chemical Change Demos
Chemical Change = Reaction
Observations of Reactants:
______________
• Liquid
•
•
•
____________
• Powder/dry
•
•
•
•Observations during the demonstration:

Reactants:
starting
I noticed
the ……
solutions in a reaction

Products: the resulting
solutions in a reaction
Question
Answer
Chemical
Change = Reaction
A chemical reaction

between two materials
occurs if the properties
of the products (what
you make) are different
from the reactants
(what you mix). Was
what you observed today
a chemical reaction?
Reactants:
starting
Explain!
solutions in a reaction

Products: the resulting
solutions in a reaction
Chemical reactions have formulas just like molecules and
Chemical
compounds.Change
As a class, we=willReaction
write the chemical equation
below and label the reactants and the products.
Chemical Formula
Reactants:
Products:

In words
Reactants:
Reactants:
starting
solutions in a reaction
Products:
 Products: the resulting
solutions in a reaction
Chemical Reaction Demo
NaHCO3
+ HOOCCH3

Sodium
Bicarbonate and
Acetic Acid
NaOOCCH3
+ H2O + CO2
Sodium Acetate,
water, and carbon
dioxide
Summary:
Chemical Change = Reaction

• How can you tell if a chemical reaction
happened?
• What are evidences to support that chemical
reaction happened?
• After a chemical reaction will it be possible to
bring back the reactants to their original form
(state and properties)?
Reactants: starting
 Products: the resulting
• How
is chemical reaction related
to chemical
solutions
in a reaction
solutions
in a reaction
change?
Signs of Chemical Change
Fizzing/gas
formation
Flash/light
smoke
Change in
temperature
Smell/odor
Change in color
Warm-up
6 March 2013
Give an example of a physical change and a
chemical change, and then describe how
they are different from the other. Explain
your answer in 2-3 sentences.
Warm-up
6 March 2013
Why is cooking/baking similar to science?
Explain your answer.
Review of Previous Knowledge
3/6/2013
Match the following description with the list of
terms below.
______ 1. Thermal energy is given off.
______ 2. Precipitate forms.
______ 3. Nitrogen dioxide forms.
______ 4. Bleach spots form.
color change
energy change
solid formation
-L
gas formation
Physical Change v. Chemical Change
Make a Venn Diagram to compare the 2 types
of changes
Physical
• Does not
change to new
substance
changes
• Size, shape
and texture
(physical
properties)
• Cutting, phase
change
Chemical
• Molecules
rearrange to
form new
substance
• Signs; color,
temperature,
smoke, etc.
• Burning,
rusting
Physical Change vs. Chemical Change
Objective
To correctly identify and differentiate
physical change from chemical change.
Question
Are changes (physical and chemical)
only present inside the laboratory?
How are physical change different from
chemical change?
If physical change does not produce a
new product, then I can ….
Hypothesis
Observations:
Chemical Change = Reaction
Steps

Reactants: starting
solutions in a reaction
Physical or Chemical

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers

Reactants: starting
solutions in a reaction

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers
Breaking chocolate bar

Reactants: starting
solutions in a reaction

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow

Reactants: starting
solutions in a reaction

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,

Reactants:
starting
and marshmallow
solutions in a reaction

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,

Reactants:
starting
and marshmallow
solutions in a reaction
Chocolate melting

Products: the resulting
solutions in a reaction
Observations:
Chemical Change = Reaction
Steps
Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,

Reactants:
starting
and marshmallow
solutions in a reaction
Chocolate melting
Eating smore!

Products: the resulting
solutions in a reaction
Discussion/Summary:
Chemical Change = Reaction
• How will you know if an object underwent
a chemical or physical change?
• Can changes happen outside of the
science classroom or laboratory?

Reactants: starting
solutions in a reaction

Products: the resulting
solutions in a reaction
Physical Change v. Chemical Change
Make a Venn Diagram to compare the 2 types
of changes
Is it a chemical or physical change?
 Sugar
dissolving in
tea
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 Logs
burning
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 Breaking
water up by
separating it into hydrogen
and oxygen
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 Cutting
paper
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 Crushing
an
aspirin
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 Metal
rusting
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 An
egg rotting
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Is it a chemical or physical change?
 An
egg breaking
•Chemical Change
•Physical Change
OOPS!
Did it change size, color, shape (Physical
Change)?
or
Did it become different matter (Chemical
Change)?
Correct!
Endothermic and Exothermic
Reactions
Standards 8.5.c.
I know chemical reactions
usually liberate or
absorbs heat.
When chemical reactions occur, the
connections between atoms must be
broken and rearranged. In order to do
Heat
this, ________________
is involved in
all chemical reactions.
There are 2 Types of Reactions Involving
Heat
Endothermic
Exothermic
• Outside-Heating
• Within-Heating
• Exo = Exit
• Endo = Enter
• Therm/ic = Heat
• Therm/ic = Heat
There are 2 Types of Reactions Involving
Heat (cont.)
Endothermic
Exothermic
• Reactions in which • Reactions in which
the system absorbs the system
releases heat to
heat from the
the surrounding.
surrounding.
There are 2 Types of Reactions Involving
Heat (cont.)
Endothermic
It feels:
Exothermic
It feels:
Cold
Hot
There are 2 Types of Reactions Involving
Heat (cont.)
Endothermic
Exothermic
Examples:
Examples:
• Cooking an egg
• Baking a bread
• Candle flame
• Rusting Iron
Frayer Model
Exothermic
Reaction
Frayer Model
Endothermic
Reaction
Weekly Reflection/Exit Slip
Chemical Change = Reaction

• Name 4 items you learned in this
week’s lesson.
• If Mr. Rivera will teach the lesson
again, will you want it done
differently?
• If
you want it done
differently,
why
Reactants:
starting
 Products:
the resulting
solutions in a reaction
solutions in a reaction
and how would you want
it?
• If you want it done the same, why?