Transcript Physical vs. Chemical Changes

Physical vs. Chemical Changes
Warm-up
8 April 2015
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
Standard
8 April 2015
5.a. I know reactant atoms and molecules
interact to form products with different
chemical properties.
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
= Reaction
A chemicalChange
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? Explain!
Reactants: starting
solutions in a reaction

Products: the resulting
solutions in a reaction
Chemical reactions have formulas just like molecules and
compounds.Change
As a class, we will
the chemical equation below
Chemical
= write
Reaction
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
8 April 2015
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
8 April 2015
Why is cooking/baking similar to science?
Explain your answer.
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, and

Reactants:
starting
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, and

Reactants:
starting
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, and

Reactants:
starting
marshmallow
solutions in a reaction
Chocolate melting
Eating smore!

Products: the resulting
solutions in a reaction
Discussion/Summary:
Chemical
• How Change
will you know=if Reaction
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
• Reactions in which
the system absorbs
heat from the
surrounding.
Exothermic
• Reactions in which
the system releases
heat to the
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
and
how
would
you
want
it?
Reactants: starting
 Products: the resulting
solutions
a reaction
• inIfa reaction
you want it done thesolutions
same, inwhy?