midterm Flashcards
5 traditional areas of chemistry
organic
inorganic
biochem
analytical (quantitative and qualitative)
physical
crystalline solid
long-range, repeating order
amorphous solid
no order
decanting
gradually pouring a liquid from one container to another without disturbing the sediment
distillation
mixture is heated to boil off the more volatile (easily vaporable) liquid, then the liquid is re-condensed in a condenser and collected in a separate flask
filtration
used to separate a mixture of an insoluble solid and liquid
physical property
property that a substance displays without changing its composition
ex. taste, color, melting point, density
chemical property
property that substance displays only by changing its composition via a chemical change
-often indicated by temperature, color change, gas production
ex. flammability, corrosiveness, flammability
physical change
alters physical state/appearance of matter (no change in composition)
ex. water boiling
chemical change
alters the composition of matter
ex. iron rusting
Kelvin calculations:
K = C + 273
C = K - 273
Fahrenheit calculations:
F = 1.8 (C) + 32
C = (F - 32) / 1.8
error =
experimental value - accepter value
percent error =
|error|/accepted value x100
error| / accepted value x 100%
density =
mass/volume
volume =
mass/density
length x width x height
mass =
density x volume
density _ as temperature _
decreases, increases
democritus contributed:
atoms were indivisible and indestructible
democritus limited:
didn’t explain chemical behavior
lacked experimental support
dalton contributed:
all elements are composed of atoms
atoms of the same element are identical
atoms of one element are different than atoms of another element
Law of Definite Proportions
chemical reactions occur when atoms are separated, joined, or rearranged
atoms of one element are never changed into atoms of another element in a chemical reaction
Law of Definite Proportions
atoms of different elements can physically mix together/combine in simple whole-number ratios to form compound
thomson contributed:
cathode ray tube experiment
electrons
plum pudding model
cathode ray tube experiment
electric currents passed through gases in a cathode ray tube
cathode ray traveled from the cathode to the anode
cathode ray deflected by a magnet
cathode ray deflected by charged plates
plum pudding model
showed an atom has electrons evenly dispersed throughout
rutherford contributed:
gold foil experiment
the atom is mostly empty space and all the positive charge and almost all of the mass comes from the nucleus
gold foil experiment
directed a narrow beam of alpha particles at a very thin sheet of gold foil
alpha particles scattered from the gold foil
rutherford was limited:
didn’t explain chemical properties of elements
why negatively charged electrons were not pulled into the positively-charged nucleus
why atoms don’t glow
law of conservation of mass
in a chemical reaction, matter is neither created nor destroyed
law of definite proportions
all samples of a given compound have the same proportions of their constituent elements
law of multiple proportions
when two elements (A and B) form two different compounds, the masses of element B that combine with element A can be expressed as a ratio of small whole numbers
of neutrons =
mass # - atomic #
avg. atomic mass =
calculate mass contributions
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