CHEM 111 1.1-1.6, 2.1-2.4

vocab

intrinsic characteristics of an element

• do NOT depend on the amount/size of sample

• ex: density, mp, bp, pH, color

homogeneous mixture

• uniform composition

• appears visually same throughout

• also called a SOLUTION

• ex: gatorade

heterogeneous mixture

• composition varies

• ex: oil + vinegar, or milk (smaller fat particles but still separate in mixture)

pure substances

• cannot be broken down into simpler substances through chemical change

• 1 type of element

compound

• pure substances that CAN be broken down through chemical change

• 2+ types of elements

• ex: H2O

density

D=M/V

• g/cm³ (s, l)

• g/L (g)

accuracy vs. precision

• accurate: result is close to real/accepted value

• precise: results are close to each other but not the accepted value

ALWAYS sig figs

• non-zero digits

• captive 0s

• trailing 0s (to right of decimal point or w/ scientific notation!!)

NEVER sig figs

• leading 0s

• trailing 0s (w/o decimal point or scientific notation)

adding/subtracting sig figs

• same # of sig figs after decimal as value w/ least digits after the decimal point

multiplying/dividing sig figs

• same as term w/ least sig figs

isotopes

• atoms of SAME element

• differ in mass

ex:

isomers

• compounds w/ SAME chemical formula

• different molecular structures

atomic mass

• (avg atomic mass of the isotopes of an element)

• avg atomic mass = sum of(%abundunce x atomic mass of isotope)

mass #

protons + neutrons

atomic #

• unique for every element!

protons

charge

protons - electrons