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

Differentiate the meaning of chemical change and physical change Objectives Differentiate the meaning of chemical change and physical change

Vocabulary Chemical change Physical change

Crumble a piece of paper What are the differences? Investigate: Crumble a piece of paper Rip a piece of paper Burn a piece of paper What are the differences?

List some examples of Physical Change cutting, freezing, boiling does NOT produce a new substance Commonly associated with the phase change diagram Solid liquid gas

What Exemplifies a Chemical Change? Materials combine to form a new substance Burning paper Rusting Iron

Digestion has both Physical and Chemical Changes Chewing of food by teeth into smaller pieces Stomach/Small Intestine breaks down food into individual molecules (fats, sugars, amino 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.

Gas or precipitate (solid) produced Name at least 5 clues that would indicate there has been a chemical change in matter. color energy change odor Gas or precipitate (solid) produced not easily reversed

Odor Change

Color Change

Energy Change

Precipitate

Not easily reversed

PHYSICAL CHANGES MELTING FREEZING 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

Reverse of Vaporization is called CONDENSATION 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

Summary REVIEW VOCABULARY –

Class Activity: Worksheets Concepts 12-4

AIM: What are habitats and niches? Homework: INTERNET QUESTIONS Paragraph