1. Compounds and Mixtures
notes

2. 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)

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

4. 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)

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

6. (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

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

8. 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

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

10. 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.

11. 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

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

13. 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.

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

15. 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

16. 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