Physical vs. Chemical Changes -...
Transcript of 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
-L
3/6/2013 Review of Previous Knowledge
______ 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.
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. Physical changes
2. Chemical changes
Physical Changes
Matter changes form WITHOUT becoming something new – You start and end with same thing (see below)
Examples: cutting, freezing, melting, etc.
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
Reactants:
Products:
Chemical Change = _________________ In chemical changes, atoms and molecules re-arrange to form new substances.
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
______________
• Liquid • • •
____________
• Powder/dry • • •
I noticed the ……
Mixing Things Up: Chemical Change Demos Observations of Reactants:
•Observations during the demonstration:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Question Answer
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? Explain!
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Chemical reactions have formulas just like molecules and compounds. As a class, we will write the chemical equation below and label the reactants and the products.
Reactants:
Products:
Reactants:
Products:
Chemical Formula
In words
Chemical Reaction Demo
NaHCO3 NaOOCCH3
+ HOOCCH3 + H2O + CO2
Sodium Acetate,
water, and carbon
dioxide
Sodium
Bicarbonate and
Acetic Acid
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Summary:
• 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)?
• How is chemical reaction related to chemical 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.
-L
3/6/2013 Review of Previous Knowledge
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
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
• Size, shape
and texture
(physical
properties)
• Cutting, phase
change
Chemical
• Molecules
rearrange to
form new
substance
• Signs; color,
temperature,
smoke, etc.
• Burning,
rusting
changes
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?
Hypothesis If physical change does not produce a new product, then I can ….
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,
and marshmallow
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,
and marshmallow
Chocolate melting
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Steps Physical or Chemical
Breaking graham crackers
Breaking chocolate bar
Cooking Marshmallow
Stacking cracker, chocolate,
and marshmallow
Chocolate melting
Eating smore!
Observations:
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Discussion/Summary:
• How will you know if an object underwent a chemical or physical change?
• Can changes happen outside of the science classroom or laboratory?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
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)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
OOPS!
Did it change size, color, shape (Physical Change)?
or
Did it become different matter (Chemical Change)?
Standards 8.5.c.
I know chemical reactions
usually liberate or
absorbs heat.
Endothermic and Exothermic Reactions
When chemical reactions occur, the
connections between atoms must be
broken and rearranged. In order to do
this, ________________ is involved in
all chemical reactions.
Heat
There are 2 Types of Reactions Involving Heat
Endothermic Exothermic
• Within-Heating • Endo = Enter • Therm/ic = Heat
• Outside-Heating • Exo = Exit • Therm/ic = Heat
There are 2 Types of Reactions Involving Heat (cont.)
Endothermic Exothermic
• Reactions in which the system absorbs heat from the surrounding.
• Reactions in which the system releases heat to the surrounding.
There are 2 Types of Reactions Involving Heat (cont.)
Endothermic Exothermic
It feels: 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
Chemical Change = Reaction
Products: the resulting
solutions in a reaction
Reactants: starting
solutions in a reaction
Weekly Reflection/Exit Slip
• 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?
• If you want it done the same, why?