Physical vs. Chemical Changes

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Physical vs. Chemical Changes
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Warm-up
21 October 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
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Standard
21 October 2013
5.a. I know reactant atoms and molecules interact
to form products with different chemical
properties.
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Physical Property Chemical Property    
Example Example      
Physical Change   Chemical Change
Example   Example  
Signs of a physical change Signs of a chemical change
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Whats the Difference?

• Matter can change
• Examples Freeze, cut, burn, etc.
• 2 types of changes
• Physical changes
• Chemical changes

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Physical Property

• Characteristic of matter that does not change the
  substance (using senses)

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Physical Changes

• Matter changes form WITHOUT becoming something
  new
• You start and end with same thing (see below)
• Examples cutting, freezing, melting, etc.

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Molecules in Physical Changes
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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

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Chemical Changes

• Matter changes, becomes NEW substance
• Start and end with different things
• Usually irreversible (cant change back)
• Examples burning, rusting, milk going sour

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Signs of Change

• Physical
• Size
• Shape
• Texture

• Chemical
• Temperature
• Color
• Bubbles/fizzing
• Smoke
• Smell

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Chemical Change _________________ In chemical
changes, atoms and molecules re-arrange to form
new substances.
Reactants   Products
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Molecules in Chemical Changes

• The atoms arrange to make a new substance

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Chemical Change Reaction
Mixing Things Up Chemical Change
Demos Observations of Reactants
______________ Liquid ____________ Powder/dry

• Observations during the demonstration

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

  I noticed the    
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Chemical Change 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!

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change 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.
Chemical Formula
Reactants     Products
In words
Reactants     Products

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Reaction Demo

• NaHCO3 NaOOCCH3
• HOOCCH3 H2O CO2

Sodium Acetate, water, and carbon dioxide
Sodium Bicarbonate and Acetic Acid
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Chemical Change 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?

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Signs of Chemical Change
Fizzing/gas formation
Flash/light
smoke
Change in temperature
Change in color
Smell/odor
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Warm-up
21 October 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.
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Warm-up
21 October 2013
Why is cooking/baking similar to science? Explain
your answer.
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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 .
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Chemical Change Reaction
Observations
Steps Physical or Chemical
 
 
 
 
 
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
 
 
 
 
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
Breaking chocolate bar  
 
 
 
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
Breaking chocolate bar  
Cooking Marshmallow  

 
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
Breaking chocolate bar  
Cooking Marshmallow  
Stacking cracker, chocolate, and marshmallow  
 
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
Breaking chocolate bar  
Cooking Marshmallow  
Stacking cracker, chocolate, and marshmallow  
Chocolate melting  
 

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change Reaction
Observations
Steps Physical or Chemical
Breaking graham crackers  
Breaking chocolate bar  
Cooking Marshmallow  
Stacking cracker, chocolate, and marshmallow  
Chocolate melting  
Eating smore!  

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Chemical Change 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?

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction

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Physical Change v. Chemical Change

• Make a Venn Diagram to compare the 2 types of
  changes

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Is it a chemical or physical change?

• Sugar dissolving in tea

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• Logs burning

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• Breaking water up by separating it into hydrogen
  and oxygen

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• Cutting paper

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• Crushing an aspirin

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• Metal rusting

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• An egg rotting

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Is it a chemical or physical change?

• An egg breaking

• Chemical Change

• Physical Change

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OOPS!

• Did it change size, color, shape (Physical
  Change)?
• or
• Did it become different matter (Chemical Change)?

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Correct!
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Endothermic and Exothermic Reactions

• Standards 8.5.c.
• I know chemical reactions usually liberate or
  absorbs heat.

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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
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There are 2 Types of Reactions Involving Heat


Endothermic
Exothermic

• Outside-Heating
• Exo Exit
• Therm/ic Heat

• Within-Heating
• Endo Enter
• Therm/ic Heat

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There are 2 Types of Reactions Involving Heat
(cont.)
Endothermic Exothermic

• Reactions in which the system releases heat to
  the surrounding.

• Reactions in which the system absorbs heat from
  the surrounding.

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There are 2 Types of Reactions Involving Heat
(cont.)
Endothermic Exothermic
It feels It feels
Cold
Hot
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There are 2 Types of Reactions Involving Heat
(cont.)
Endothermic Exothermic
Examples Examples

• Candle flame
• Rusting Iron

• Cooking an egg
• Baking a bread

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Frayer Model
Exothermic Reaction
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Frayer Model
Endothermic Reaction
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Chemical Change Reaction
Weekly Reflection/Exit Slip

• Name 4 items you learned in this weeks 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?

• Products the resulting solutions in a reaction

• Reactants starting solutions in a reaction