2.  Physical Property- a property that can be observed and measured without changing the identity of the substance.  Examples- Viscosity, density, melting- point  Chemical Property-relates to a substance’s ability to undergo changes that transform it into different substances.  Example-Alkali metals are highly reactive to water and halogens to form ionic compounds

3.  Chemists use properties to identify and separate matter. More than one property must be used for identification.  Intensive Properties – do not depend on the amount of matter present Ex. Melting pt., boiling pt, density, conduct electricity  Extensive Properties – depend on the amount of matter present Ex. Volume, mass

4.  A physical change does not change the composition or identity of the substance.  Examples?  Boiled water is still water.  All phase changes are physical changes

5. Solid Liquid Gas Mel t Evaporat e Condens e Freeze

6.  Sublimation is a process in which a solid changes directly to a gas without going through the solid phase.  Examples: dry ice  CO 2

7.  A chemical change occurs when one or more substances are changed into new substances.  Reactants- substances that react  Products- substances that form  Products have NEW PROPERTIES

8. Indications of chemical change 1.) Production of heat, light, sound, or electricity 2.) Production of a gas 3.) Formation of a precipitate 4.) A change in color 5.) A change in odor

9. Energy Changes Some changes in matter release energy. For example, the explosion that occurs when hydrogen and oxygen react to form water is a release of energy. Heat energy and light energy are released as the reaction takes place.

10. Energy Changes A change in matter in which energy is absorbed from the surroundings is an endothermic process (heat enters). EXAMPLES: melting ice & boiling water When barium hydroxide reacts ammonium nitrate are mixed the test-tube feels cold to touch because energy has been absorbed

11. Energy Changes A change in matter in which energy is released is an exothermic process (heat exits). Examples: freezing water & condensation Burning of paper gives off heat to the surroundings.