Compounds and Mixtures notes

Molecule 2 or more atoms held together by CHEMICAL BONDS Can be 2 of the same element (O2) It is the smallest unit of a compound (remember: atom is smallest unit of matter that can’t be broken down naturally; cell is smallest unit of life)

Compound 2 or more different elements held together by CHEMICAL BONDS EX: Water = H2O Salt =NaCl Sugar= C6H12O6 Carbon dioxide= CO2

Properties of a Compound: Compounds have different properties than the original elements that made them Ex: Sodium (Na) is explosive Chlorine (Cl) is poisonous Together, NaCl is delicious on popcorn! (Salt)

(Properties continued) 2. Compounds cannot be separated by physical means (only chemical reactions) YES NO

(Properties continued) 3. Compounds are always made of exactly the same thing, in the same numbers. ex: water (H2O) is always 2 H’s and 1 O. carbon dioxide (CO2) is always 1 C and 2 O

Pure Substances Elements and compounds are PURE They are made of only 1 type of atom or molecule

Element Symbols (you should know this) B, Fe, C, O, Sn, Ag, Au, etc… These are symbols found on the Periodic Table of Elements Each is an individual element made of one type of atom

Compound Formula notation MgO (magnesium + oxygen) NaCl (sodium + chlorine) NO NUMBERS so there is only 1 of each atom in the molecule

Numbers after the symbol… NH4 =1 Nitrogen and 4 Hydrogen (ammonia) H2O2 =2 hydrogen and 2 oxygen (hydrogen peroxide) Fe2O3 =2 Iron and 3 oxygen (rust) …tells how many atoms of that element there are in the molecule.

Numbers after parenthesis C7H3(NO2)3 =7C; 3H; 3N; 6oxygen (TNT) Ca(H2PO4)2 =1Ca; 4H; 2P; 8oxygen (fertilizer) Mg(OH)2 =1Mg; 2oxygen; 2H (milk of magnesia …means multiply the contents of the parenthesis

Predicting Combinations of Elemenets Metal & metal…UNLIKELY compound Metal & nonmetal…Yes, called an ionic bond Nonmetal & nonmetal…Yes, called a covalent bond

Mixtures Are formed when substances combine in a physical way Can be separated in a physical way “Physical” includes dissolving, melting, mixing, evaporating, filtering or just picking out the pieces.

Types of Mixtures Heterogeneous mixtures Ex: NOT well mixed Different substances that remain physically separate Ex: Sand Pizza Salad and salad dressing Fruit Loops

Types of Mixtures (cont.) Homogeneous mixtures Uniform; well mixed Includes solutions Ex: cup of coffee or tea or soda Mouthwash Air (oxygen, nitrogen, argon, carbon dioxide) Metal alloys (steel, bronze) Salt water

Types of Mixtures (cont.) Solutions A liquid mixture The solute (smaller ingredient) is dissolved in the solvent (larger, liquid ingredient) Ex: salt water Choc. powder in milk Coffee milk