AIM: What are chemical and physical changes? What are chemical and physical changes?

AIM: What are chemical and physical changes?

What are chemical and physical changes?


Differentiate the meaning of chemical change and physical change


Chemical changeChemical change

Physical changePhysical change

Chemical changeChemical change

Physical changePhysical change


Investigate:

Crumble a piece of paperCrumble a piece of paper

Rip a piece of paperRip a piece of paper

Burn a piece of paperBurn a piece of paper

What are the differences?What are the differences?

Crumble a piece of paperCrumble a piece of paper

Rip a piece of paperRip a piece of paper

Burn a piece of paperBurn a piece of paper

What are the differences?What are the differences?


List some examples of Physical Change

1.1. cutting, freezing, boiling cutting, freezing, boiling 2.2. does NOT produce a new does NOT produce a new

substancesubstance3.3. Commonly associated with the Commonly associated with the

phase change diagram phase change diagram 4.4. Solid liquid gasSolid liquid gas

1.1. cutting, freezing, boiling cutting, freezing, boiling 2.2. does NOT produce a new does NOT produce a new

substancesubstance3.3. Commonly associated with the Commonly associated with the

phase change diagram phase change diagram 4.4. Solid liquid gasSolid liquid gas


What Exemplifies a Chemical Change?

1.1. Materials combine to form a new Materials combine to form a new substancesubstance

2.2. Burning paperBurning paper3.3. Rusting IronRusting Iron

1.1. Materials combine to form a new Materials combine to form a new substancesubstance

2.2. Burning paperBurning paper3.3. Rusting IronRusting Iron


Digestion has both Physical and Chemical Changes

1.1. Chewing of food by teeth into Chewing of food by teeth into smaller piecessmaller pieces

2.2. Stomach/Small Intestine breaks Stomach/Small Intestine breaks down food into individual down food into individual molecules (fats, sugars, amino molecules (fats, sugars, amino acids)acids)

1.1. Chewing of food by teeth into Chewing of food by teeth into smaller piecessmaller pieces

2.2. Stomach/Small Intestine breaks Stomach/Small Intestine breaks down food into individual down food into individual molecules (fats, sugars, amino molecules (fats, sugars, amino acids)acids)


Definition

• Chemical change: The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.”


Examples

• Physical Changes • Aluminum foil is cut in • Clay is molded into a new

shape.• Butter melts • Water evaporates from

the surface of the ocean.• a juice box in the freezer

freezes.• .Rubbing alcohol

evaporates on your hand

• Chemical Changes• Milk goes sour.• Jewelry tarnishes. • Bread becomes toast. • Rust forms on a nail left

outside.• Gasoline is ignited.• Hydrogen peroxide

bubbles in a cut.



Name at least 5 clues that would indicate there has been a chemical

change in matter. 1. color

2. energy change3. odor

4. Gas or precipitate (solid) produced 5. not easily reversed


Odor Change


Color Change


Energy Change


Precipitate


Not easily reversed


PHYSICAL CHANGES

MELTING

• solid to liquid

• As the ice gains energy – more molecules vibrate

• eventually the bonds that form the ice crystals break and the ice melts.

FREEZING

• the reverse: looses thermal energy

• The molecule move about more slowly

• Eventually the ice crystal start to form


Vaporization

EVAPORATION

• Water slowly gains energy

• Gradually converts to gas

• “sweating”

BOILING

• Water rapidly gains energy

• Quickly converts to gas

Reverse of Vaporization is called CONDENSATION


SOLID > GAS

SUBLIMATION

Dry Ice


Practice Quiz

• http://www.mrzimmerman.org/OnLineQuizPage/Chem%20Practice.htm


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AIM: What are chemical and physical changes? What are chemical and physical changes?