In 1927, Columbia Phonograph Broadcasting In 1927, Columbia Phonograph Broadcasting System went on the air with 47 radio stations. System went on the air with 47 radio stations. However, the radio network lost money in its first However, the radio network lost money in its first year, and on 18 Jan 1929 Columbia Records sold year, and on 18 Jan 1929 Columbia Records sold out to a group of private investors for $400,000, out to a group of private investors for $400,000, headed by William S. Paley, a Philadelphia cigar headed by William S. Paley, a Philadelphia cigar manufacturer. The radio network was renamed The manufacturer. The radio network was renamed The Columbia Broadcasting System (CBS).Columbia Broadcasting System (CBS).

September 18th, 2015

SciFirSciFir Discuss Book Discuss Book Discuss chemical and physical Discuss chemical and physical

properties properties

SciFri September 18SciFri September 18thth, 2015 Bamboo Cycle , 2015 Bamboo Cycle Rolls Out Rolls Out

Changes in PropertiesChanges in Properties

Goals: describe coming physical Goals: describe coming physical and chemical changesand chemical changes

Determine between chemical and Determine between chemical and physical properties physical properties

Identify intensive and extensive Identify intensive and extensive characteristics characteristics

Suggested Reading: section 3.2 Suggested Reading: section 3.2 changes in properties pages 56 -62changes in properties pages 56 -62

A reaction where a new substance is formed.

Chemical bonds are broken and reformed.

Difficult to reverse the reaction.

Formation of a gas

Color change (that is not a result from dilution or color mixing

Emission or absorption of heat (temperature change)

Formation of a Precipitate

Emission of light

Iron rusting

Leaves changing colors

Fruit ripening

Wood burning

Reactions that absorb energy

Get “endo” the house, because it’s COLD!

Endothermic processes

melting ice cubes

conversion of frost to water vapor

evaporation of water

forming a cation from an atom in the gas phase

baking bread

cooking an egg

producing sugar by photosynthesis

separating ion pairs

melting solid salts

Reactions that give off Heat

Explosion !

Exothermic processes

making ice cubes

formation of snow in clouds

condensation of rain from water vapor

a candle flame

mixing sodium sulfite and bleach

rusting iron

burning sugar

mixing water with calcium chloride

State change

Form change – ripping, tearing, bending, size change

Dissolving

Magnetization

No new substance is formed.

No chemical bonds are broken and reformed.

Easy to reverse the reaction.

The form or state of a material may change but not its basic composition or properties.

What is a property?What is a property?

PropertyProperty: a : a characteristic of a characteristic of a substance that substance that can be observedcan be observed

Physical Property Physical Property

Physical property: a property that can be observed without changing the identity of the substance.

Examples:

• luster

• malleability: the ability to be hammered into a thin sheet

• ductility: the ability to be stretched into a wire

• melting point

• boiling point

• density

• solubility

• specific heat

Special Physical PropertiesSpecial Physical Properties

Melting pointMelting point: the temperature at : the temperature at which a substance changes from a which a substance changes from a solid to a liquid at a given pressure solid to a liquid at a given pressure

water = 0water = 0ooCC

Boiling pointBoiling point: the temperature at : the temperature at which a substance changes from a which a substance changes from a liquid to a gas at a given pressureliquid to a gas at a given pressure

water = 100water = 100ooCC

Chemical PropertiesChemical Properties

Chemical propertyChemical property: a property that : a property that can only be observed by changing can only be observed by changing the identity of the substancethe identity of the substance

Examples:

•flammability

•ability to rust

•reactivity with vinegar

Intensive/Extensive Properties

AssignmentAssignment

NoneNone Unit exam Wednesday, September Unit exam Wednesday, September

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