Walz (H) midterm vocab

accuracy

closeness of a measurement to an accepted value

precision

-clustering of related measurements closely to one another (keep getting the same #s... reproducibility)

-following the measurement rule & reading the instrument to the proper # of digits

homogeneous mixture

uniform throughout, even distribution of particles

heterogeneous mixture

not uniform, not evenly distributed, can tell components apart

ionic bond

they form when electrons are transferred between cations (+) and anions (-), an attraction between oppositely charged ions (NM&M)

covalent bond

form when electrons are shared between atoms (usually NM)

-3 types: single bonds, double bonds, triple bonds

ion

when an atom loses or gains an electron, it has a + or - charge

monatomic ion

a charged particle made up of a single atom

polyatomic ion

ions bonded together by covalent bonds, ions consist of more than one atom
**more polyatomic anions

cation

positively charged ions

anion

negatively charged ions

isotope

atoms that have the same proton number but different neutron number

group (family)

Vertical column in the periodic table, there's 18
**same group=same val e-

period (row or series)

horizontal rows on the PT, there's 9
**same period=same energy level (tells how many energy levels there are)

density

mass per unit volume of a substance, changes with temp & pressure

hypothesis

-a concept or idea that's tested through experiments or research
-an educated guess/prediction

theory

a well supported explanation of observations/experiments already tested

chemical change

-a change in which one or more substances are converted into a different substance

-change in identity

physical change

-a change that does NOT involve a change in identity

-same chemical substance

-all phase changes fall into this category

mole

-a unit of quantity or count in chemistry, forms a bridge between particle amounts & gram amounts of chemicals

-3 main ones in chemistry: atoms, molecules, formula units

Avogadro's number

tells the number of particles in a mole

(6.02x10^23)

empirical formula

gives the same info as the molecular formula but in lowest ratio

molecular formula

gives symbols & subscripts to represent what elements are present & their atoms

half-life

-measure rate of decay of radioisotopes

-one half life is the time it takes for half of the atoms in a sample to decay into a new element

Law of Conservation of Mass

matter canNOT be created or destroyed, it can only be rearranged