How is Matter Classified? •  Matter is classified using chemical and

physical props.

Pure Substances •  a sample of matter that has definite chemical

and physical properties •  Elements •  Compounds

ATOM •  the basic unit of matter •  all matter is composed of atoms

ELEMENTS •  simplest substances from which more

complex substs. are made •  ea. elem. contains single type of atom •  111 diff. elements discovered to date •  represented by symbols – usually one or two

letters

1st letter is always capitalized, second letter is always sm. case

•  most symbols come from their names •  some symbols come from Latin or Greek names •  some elem. named in honor of person or place they

were discovered •  ea. elem. has its own unique set of chem. and

physical props.

Small number of elements make up most common substs.

•  H is most common element •  Living things are made primarily of C, H, O,

and N

MOLECULE •  neutral group of atoms held together by

covalent bonds •  two or more atoms combined in a definite ratio •  atoms may be of the same or different elements

Elements may exist as single atoms or as molecules

•  Helium gas consists of single atoms (monatomic gas) •  Nitrogen gas consists of molecules

•  Ea. molec. consists of two nitrogen atoms (diatomic gas)

7 diatomic gases are elements: •  Bromine •  Iodine •  Nitrogen

•  Chlorine •  Hydrogen •  Oxygen •  Fluorine

ALLOTROPES •  one of a number of different molecular or

crystalline forms of an element •  diff. forms of the same element •  Oxygen consists of 2 allotropes – O2 and O3

(ozone) •  Carbon has many allotropes

•  most common are graphite and diamond

•  Allotropes have different properties

COMPOUND •  the product that results when two or more

different elements are chemically combined

Two types of compounds: •  Ionic compounds – consist of positively and

negatively charged ions •  ION – an atom or group of atoms w/ an electrical

charge •  Covalent compounds – made of neutral

molecules

ACID •  a class of compounds whose water solns. taste

sour, turn blue litmus paper red, and react with bases to form salts (ionic compounds)

pH •  a numerical scale used to express acidity •  0 to 14 •  7 is neutral

•  comps. w/ pH less than 7 are acids •  comps. w/ pH greater than 7 are bases

BASE •  a class of compounds that taste bitter, feel

slippery in water soln., turn red litmus to blue, and react with acids to form salts

ORGANIC COMPOUNDS •  covalent compounds containing carbon

(except carbonates and oxides)

INORGANIC COMPOUNDS •  compounds outside the organic family of

compounds

Compounds are represented by formulas

•  molecular formula - C12H22O11 (sugar) •  ionic formula – NaCl (table salt) •  shows numbers of atoms of ea. elem. present in

compound

Structural Formulas •  show the exact number of atoms present in a

molecule and how these atoms are bonded to one another •  lines represent the bonds betw. atoms

MIXTURE •  a collection of 2 or more pure substs.

physically mixed together •  proportions can vary •  properties can vary

ALLOY •  solid mixture (usually mixture of metals)

Two diff. classifications of mixtures:

HOMOGENEOUS MIXTURE •  a mixture containing substs. that are uniformly

distributed •  solution

•  salt water •  koolaid •  tea •  brass (alloy)

•  all regions are identical in composition & properties

HETEROGENEOUS MIXTURE •  a mixture containing substs. that are not

uniformly distributed •  some regions have different properties than other

regions •  dirt •  granite •  choc. chip ice cream •  veg. soup •  ice water

How mixtures differ from compounds:

•  Props. of mixtures reflect props. of components. Props. of compounds do not •  reflect. props. of elems. that compose it.

•  Comps. have definite composition. Composition of mixtures can vary.

Most mixtures can be separated by physical means. Some mixtures

may need to be separated by chemical means.

•  react one component so it can be removed easier

All compounds must be separated by chemical means