Matter Notes
Mixture vs. Pure Substance
Compound vs. Element
sample of matter
Can it be separated by physical means?
YES
NO
MIXTURE
PURE SUBSTANCE
(> 1 kind of atom and/or compound)
(only 1 kind of atom OR compound)
Is the composition uniform?
Can it be decomposed by
ordinary chemical means?
YES
NO
YES
HOMOGENEOUS
HETEROGENEOUS
NO
COMPOUND
(> 1 kind of atom)
ELEMENT
(only 1 kind of atom)
One atom?
Monatomic
Two atoms?
Diatomic
Three atoms?
Triatomic
More than one form?
Allotropic


O2, O3
graphite,
diamond,
buckyballs
graphene (single
layer of C atoms)
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Matter Notes
Elements and Compounds
Element:

simplest form of matter – contain only 1 kind of atom

cannot be broken down further by chemical means,
e.g. C, N2, O2, H2
Compound:

made up of 2 or more elements

can be broken down chemically,
e.g. H2O, NH3, CO2
Example of the breakdown of a compound  its elements
cane sugar C12H22O11
chemical
change
C + H2O
(element) (compound)
chemical
change
H2 + O2
(element) (element)
Note: In general, chemical and physical properties of elements DIFFER from those of the
compounds they make.
Physical Separation of Mixtures
Process
Property
Filtration
solubility
Crystallization
solubility
Evaporation
boiling point
Distillation
boiling point
Centrifuge
density
Decant
density
Magnetism
magnetism
Sifting
size or shape
Chromatography
size/polarity/charge
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Matter Notes
Filtration
Decant
Substance must be
dissolved or suspended in
water (or other solvent)
Denser solid drops to bottom of
beaker, liquid can then be
poured off the top
Distillation
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Matter Notes
What is Chromatography?
The separation of chemical substances by differential movement through a two-phase system
Applications in chemistry:
Analytical chemistry – separating out components of a mixture before identifying each
component
Synthetic chemistry – purifying compounds
History
Earliest chromatography – Mikhail Tswett – 1906 – separated plant pigments (colored, hence
“chroma”) by paper chromatography.
Some Chromatography Terms
Mobile phase = the phase which moves across the stationary phase, into which the sample is
often placed
Stationary phase = the phase which remains in the same place, over which the mobile phase
moves, may be attached to or contained within a support
In paper chromatography, the stationary phase is paper, while the mobile phase is some
type of liquid, e.g. salt water. This is a type of adsorption chromatography.
How does paper chromatography work?
The components of the mixture are dissolved in a solvent (mobile phase). The solvent rises
through the paper (stationary phase) using capillary action. The distance a particular
component moves along the paper depends upon its attraction to the paper compared with its
attraction to the solvent. If it is more attracted to the paper, it will not move very far along the
paper. If it is more attracted to the solvent, it will move further along the paper. In this way the
components of the mixture become separated.
We can compare different components of mixtures by measuring their Rf values.
Rf = distance component of mixture moved up the paper
distance solvent moved up the paper
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