2011年10月19日星期三

Matter & Chemical and Phsical Change

 MATTER?
----Anything that has mass and takes up space.
                                 
Matter
includes
1.Pure Substances                                             
---one set of properties
---one kind of particle
(1) Element
---simplest form(cannot be decomposed)
---made of atoms 1.metal  2.nonmetal 3.metalloid
(2)compounds
----made of elements
---chemically combined
---smallest particle is a molecule(Ionic  &  Covalent)


2.Mixtures
---more than one set of properties and substances
---physically combined(1)Homogeneous
---uniform throughout
---appears to have only one component
Ex: Solutions &  colloid
(2)Heterogeneous
---not uniform
---appears to have more than one component
Ex:   Salad Dressing (Suspensior & Mechanical Mixture)
       Water+oil

Physical Change vs. Chemical Change
Physical Change
---no new substance is formed
---chemical composition doesn't change
---reversible


Chemical Change
---new substances are formed
---irreversible
Ex: Burning & Cooking

A few more properties for matter
---it is neither created nor destroyed(only changed form from one form to another)

Three States
(1)Solid
---rigid, don't change shape easily and experiences small changes in volume
(2)Liquid
---takes the shape of the container and experiences slight changes in volume when heated
(3)Gases
---takes the shape of the container and experiences drastic change in volume when heated

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