Mixtures, Elements, Compounds Ch. 2.2 and 2.3 Mixtures, Elements, Compounds

Symbols Chemists use chemical symbols to represent elements Chemical Symbol: 1st 1-2 letters of the name of the element 1st letter is Capitalized 2nd letter is lower case Examples: Co = Cobalt; O = Oxygen; Be = Berylium Exception: Some use the letters from the Latin name Examples: Fe = Iron (Ferrum) K = Potassium (Kalium) Cu = Copper (Cuprium)

Formulas Chemists use chemical formulas to represent compounds Compounds: 2 or more elements Examples: NaCl = Sodium Chloride H2O = Water

Na + Cl2  NaCl Sodium + Chlorine  Table salt

H2 + O2  H2O

Distinguishing Substance and Mixtures

Heterogeneous V. Homogeneous

Identifying Substances Physical Property: quality/condition of substance that can be observed or measured w/o changing substance. Color, weight, size, volume Physical Change: changing the state but not the composition. Melting, boiling, vaporizing, freezing, crushing

Identifying Substances Chemical Property: how does a substance react with another substance. Iron reacts with oxygen. Chemical Change: the reaction that takes place when two substances react. The composition changes. Also called a Chemical Reaction Iron reacts with oxygen to make rust.

Paper chromatography Separating a mixture

Law of Conservation of Mass During any chemical reaction or physical change, the mass of the products is always equal to the mass of the reactants Bottom line: you cannot create or destroy matter. Matter is conserved. What about burning wood?????