1. Elements, Compounds, and Mixtures
Classifying Matter
Elements, Compounds, and Mixtures

2. Elements
Definition: a pure substance which can not be decomposed by chemical change.
Examples: 118 known elements (88 natural-rest manmade) On periodic table.
Composed of: Atoms (smallest part of an element that can enter into a chemical reaction and combine with other elements.

3. Elements Properties: Can’t be decomposed by chemical means.
Seven elements are found in nature as diatomic elements (2 atoms). These elements are: hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine, and iodine. Rest are monatomic.
Allotropes: different forms of the same element thereby having different structures and properties. Ex: oxygen and ozone.
Representation: use symbols. One or two letters that stand for an element. First letter must be capitalized. Ex: C (carbon), Cl (chlorine), Co (cobalt), Cr (chromium), Cu (copper)

4. Compounds
Definition: a pure substance that consist of two or more elements chemically combined.
Examples: NaCl (sodium chloride), NH3 (ammonia), H2O (water)
Composed of: two or more elements forming a molecule (smallest quantity of matter that retains the physical and chemical properties of the original substance)

5. Compounds Properties:
2 or more elements chemically combined in definite proportions.
Decomposed by chemical means. Ex: Water is decomposed by electrolysis to form hydrogen and oxygen.
Representation: formulas Ex: Cu(NO3)2 contains 1 atom of copper, 2 atoms of nitrogen, 6 atoms of oxygen.

6. Mixtures Homogeneous Mixture:
Definition: 2 or more substances uniformly mixed together each retaining its original properties. It can be physically separated.
Examples: Solutions (ocean water, ice tea, lemonade)
Composed of: elements and /or compounds.
Heterogeneous Mixture:
Definition: 2 or more substances not uniformly mixed together each retaining its orignal properties. It can be physically separated.
Examples: Colloids (?)
(milk, shampoo, ketchup, lotions)
Suspensions (sand/water, salt/pepper, oil/water. cereal/milk)
Composed of: elements and /or compounds)

7. Mixtures Properties: Physically combined Physically separated
Ex: Filtration (solid from a liquid)
Distillation (different liquids
due to different boiling points)
Chromatography
Amounts of each component may vary
May be homogeneous or heterogeneous

8. Properties of Mixtures
Homogeneous Mixtures
Solutions:
Best mixed
Smallest particles
Hardest to separate
Doesn’t settle upon standing
Lacks the tyndal effect (doesn’t scatter light)
Heterogeneous Mixtures
Suspensions:
Least mixed
Largest particles
Easiest to separate
Settles upon standing
Scatters light
Note: Colloids are in a gray area the properties are in between a true solution and a suspension.

9. Mixtures Homogeneous Mixtures Representation: Symbols and/or Formulas
Example:
NaCl(aq) aqueous solution of sodium chloride in water
Heterogeneous
Mixtures
Representation:
Symbols and/or
formulas