Physical and Chemical Changes

EQ: What is the difference between physical and chemical changes?

SPI 0807.9.8

What are the physical properties of matter?

• DENSITY• SOLUBILITY• DUCTILITY• MALLEABILITY• STATE• THERMAL CONDUCTIVITY

PHYSICAL CHANGES

A physical change affects one or more physical properties of matter.

(the identity doesn’t change)

Example…

• Imagine a piece of silver that is pounded and molded into a heart-shaped pendant.

• The shape of the silver changed. Its properties are still the same! The piece of silver is still silver.

Physical changes DO NOT change the identity of the matter involved.

Even though the shape of the butter changed, the butter is still butter!

More Examples of Physical Changes:

MELTING ICE

CUTTING HAIR

MIXING SUGAR AND WATER

CHIPPING WOOD

• Mixing oil and vinegar

• Cutting Paper

• Molding Clay

• Dissolving sugar in water

More Examples:

Physical changes are REVERSIBLE

- If an ice cube melts, you could easily freeze the the liquid water to make another ice cube.

Sugar dissolves in water, but the particles do not combine.

The water and sugar can be separated.

What are the chemical properties of matter?

• FLAMMABILITY• REACTIVITY

CHEMICAL CHANGES

A chemical change occurs when one or more substances are changed into new substances

with different properties.

Chemical properties can only be observed when a chemical change takes place.

Examples of Chemical Changes:

BATTERIES

BAKING A CAKE

DIGESTION

Chemical changes change the identity of the matter involved.

An important question to ask yourself when trying to decide if a physical or chemical change happened is:

DID THE COMPOSITION CHANGE?

* COMPOSITION- The matter that makes up the object and the way the matter is arranged.

Clues to Chemical Changes:

You usually need more than one of the above characteristics to be considered a chemical change!

Fizzing and FoamingIf fizzing or foaming occurs,

this means that a gas has been produced.

This indicates a chemical change.

Example: Alka Seltzer

• Exploding Pumpkins

Color Change

• Oscillating Reaction

Test Tube Demonstration

A New Substance is Formed

Precipitate Experiment

Smell

Heat and/or Light

If the temperature is increased or decreased during a reaction, a chemical change could be taking place.

If light is created, a chemical change could be taking place.

Yeast and Peroxide Demonstration

Chemical changes cannot be undone by physical means.

Decomposing food cannot be reversed.

The formation of rust cannot be reversed.

Mentos and Coke

Balloon and Baking Soda

Potassium Chlorate and a Gummy Bear

The Statue of Liberty was originally a copper color. After being being exposed to air, she turned a greenish color.

What kind of change happened? Explain your answer.