In 1927, Columbia Phonograph Broadcasting System went on the air with 47 radio stations. However, the radio network lost money in its first year, and on 18 Jan 1929 Columbia Records sold out to a group of private investors for $400,000, headed by William S. Paley, a Philadelphia cigar manufacturer. The radio network was renamed The Columbia Broadcasting System (CBS). September 18 th, 2015

n SciFir n Discuss Book n Discuss chemical and physical properties

SciFri September 18 th, 2015 Bamboo Cycle Rolls Out

Changes in Properties n Goals: describe coming physical and chemical changes n Determine between chemical and physical properties n Identify intensive and extensive characteristics n Suggested Reading: section 3.2 changes in properties pages

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? n Property: a characteristic of a substance that can be observed

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 Properties n Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0 o C n Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100 o C water = 100 o C

Chemical Properties n Chemical property: a property that can only be observed by changing the identity of the substance Examples: flammability ability to rust reactivity with vinegar

Intensive/Extensive Properties

Assignment n None n Unit exam Wednesday, September 23 rd