How is Matter Classified?

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How is Matter Classified?

• Matter is classified using chemical and physical
  props.

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Pure Substances

• a sample of matter that has definite chemical and
  physical properties
• Elements
• Compounds

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ATOM

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

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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

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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.

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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

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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

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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)

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7 diatomic gases are elements

• Bromine
• Iodine
• Nitrogen

• Chlorine
• Hydrogen
• Oxygen
• Fluorine

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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

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COMPOUND

• the product that results when two or more
  different elements are chemically combined

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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

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ACID

• a class of compounds whose water solns. taste
  sour, turn blue litmus paper red, and react with
  bases to form salts (ionic compounds)

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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

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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

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ORGANIC COMPOUNDS

• covalent compounds containing carbon (except
  carbonates and oxides)

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INORGANIC COMPOUNDS

• compounds outside the organic family of compounds

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Compounds are represented by formulas

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

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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

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MIXTURE

• a collection of 2 or more pure substs. physically
  mixed together
• proportions can vary
• properties can vary

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ALLOY

• solid mixture (usually mixture of metals)

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Two diff. classifications of mixtures
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HOMOGENEOUS MIXTURE

• a mixture containing substs. that are uniformly
  distributed
• solution
• salt water
• koolaid
• tea
• brass (alloy)
• all regions are identical in composition
  properties

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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

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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.

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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

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All compounds must be separated by chemical means