PHYSICAL & CHEMICAL CHANGES Objectives: 1. Compare and contrast physical and chemical changes 2....

PHYSICAL & PHYSICAL & CHEMICAL CHANGESCHEMICAL CHANGES

Objectives:Objectives:

1.1.Compare and contrast physical and chemical Compare and contrast physical and chemical changeschanges

2.2.Identify examples of physical and chemical Identify examples of physical and chemical changeschanges

Why do I care?

Physical and Chemical changes occur around us everyday! Understanding them will help us better understand our world.

Changes in MatterChanges in Matter

Change: the act of altering a substance In science, we talk of two types of

changes:

physical

chemical

Physical ChangePhysical Change Physical change: a change that occurs that does

not change the identity or make up of the substance Change in state or phase (Freezing, boiling,

melting, sublimating) Changing shape (cutting, folding, twisting,

bending) Dissolving

Physical ChangesPhysical Changes Physical changes are changes that alter the size,

shape, location or physical state of a substance but not its chemical state.

Its still H2O- frozen in snowflakes, as liquid in raindrops, or as a gaseous water vapor, it’s chemical formula has not changed.

ExamplesExamples A physical change in a substance doesn't

change what the substance is. Cutting, folding, or crumpling paper –

A physical change in the shape and size of the paper. However, it is still paper! https://www.youtube.com/watch?v=kK4EMUd9eds

Dissolving sugar in iced tea- Sugar is still C6H12O6 but now it is spread out in

the liquid, it still tastes just as sweet! https://www.youtube.com/watch?v=D1dRdYPRvpY

What Other Kinds of Changes Are What Other Kinds of Changes Are Physical?Physical?

CuttingCutting TearingTearing ShreddingShredding ShrinkingShrinking EnlargingEnlarging

Change in Phase Change in Phase RelocatingRelocating RotatingRotating Molding (shaping)Molding (shaping)

Chemical ChangesChemical Changes

Chemical change: a change that occurs causing the identity of the substance to change Burning Chemically digesting food (acid and bile) Reacting with other substances

A chemical change is also called a chemical reaction

Chemical ChangesChemical Changes Chemical changes are changes that alter the

chemical make up of the substance. New matter is formed with properties that are

different than those of the original matter.

Chemical ChangesChemical Changes If you end up with a chemical or chemicals

that you did not start with. . . It is a chemical change!

Chemical ChangesChemical Changes A chemical change is not easily reversed.

Easy to reverse/change back

Difficult to reverse/change back

Signs That a Chemical Change Signs That a Chemical Change has occurredhas occurred

Creation of a gas (bubbles) https://www.youtube.com/watch?v=OBdgeJFzSec

Creation or loss of heat https://www.youtube.com/watch?v=GQkJI-Nq3Os

https://www.youtube.com/watch?v=UMEbeyKrE30

Burning Rotting/molding https://www.youtube.com/watch?v=CcuWuKLoCmU https://www.youtube.com/watch?

v=S12zZhdOckc&src_vid=OmcXo9XC6Uc&feature=iv&annotation_id=annotation_14756

Breaking down (decomposition) Precipitation https://www.youtube.com/watch?v=98dbILqPtgI

Cooking https://www.youtube.com/watch?v=n6wpNhyreDE

Rusting (oxidation)

Chemical ChangeChemical Change

Heat and light are often

evidence of a chemical change.

The strike of a match is a chemical change due to the

reaction of the chemicals with oxygen.

Burning wood turns to charcoal and ashes. This is a chemical change.

Is it Physical or Chemical?Is it Physical or Chemical?

ChangeChange PhysicalPhysical ChemicalChemical

Melting cheeseMelting cheese

Burning woodBurning wood

Milk souringMilk souring

Folding up paperFolding up paper

Bicycle rustingBicycle rusting

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