Section One

Accuracy v.s. Precision

  • accuracy: closeness to true value

  • precision- how close a series of measurements,

    more numbers = more precise

Sig Fig Rules

  1. non zeros are significant

  2. zeros between count

  3. zeros at the end don’t count unless there is a decimal point

  4. zeros before sig figs don’t count

  5. zeroes after a decimal do count, only if there was a sig fig before the decimal point

Rounding rules

  • less than 5 leave it be

  • greater than 5 round

  • equals 5 make it even

Sig figs with math

multiplication and division- least amount of sig figs

addition and subtraction- least amount of decimal places

Temp convs:

K= C +273

C= K- 273

Density conversions:

  • D=M/V

  • M= DV

  • V=M/D

Matter

  • solid: definite shape and volume, high density, slow-moving particles

  • liquid: indefinite shape, definite volume

  • gas- indefinite shape and volume, low density, easily compressed, fast-moving particles

  • intensive prop-type of matter

  • extensive prop- amount of matter

  • physical prop.- state, color, density

  • chemical prop.-oxidization, flammability

  • physical changes - cutting, melting

  • chemical changes- cutting food, rusting

  • homogenous- uniform composition

  • heterogenous- un-uniform composition

  • separating mixtures- decant, filtration, magnet, chromatography, distillation

Laws

  • law of conservation energy- energy can’t be created only changed into something else

  • law of conservation of mass- mass can not be created or destroyed, total mass is constant

  • periodic law- properties of elements repeat when placed in increasing atomic #

Period v Group

  • period- row

  • group- column

Metals, Nonmetals, Metalloids

  • metals- high luster, good conductors of heat and electricity, solids, ductile, malleable, high density, high boiling point, cations

  • nonmetals- poor conductors, mostly gases, low density and boiling point, brittle, anions

  • metalloids- prop of both metals and nonmetals, staircase

Groups in the periodic table- alkali metals, alkaline earth metals, transition metals, metalloids, nonmetals, halogens, noble gases, lanthanide, actinide

Factors influencing trends

  1. electron energy level: distance from the nucleus

  2. nuclear charge- # of protons influences the pull on electrons, going left to right

  3. shielding- valence electrons are shielded from the charge of the nucleus by electrons in between, up and down