Transcript I. States of Matter

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Chemistry – studies matter and the physical
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Branches of study include:
and chemical changes it undergoes
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Organic – carbon compounds (DNA, etc)
Inorganic – non carbon cpds (medicines,etc)
Physical – matter/energy changes (atoms)
Analytical – material makeup (geometry of atoms)
Biochemistry – chemistry of living things
Theoretical – use of physics to understand chemical
phenomena (quantum chemistry)
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Matter- anything that has mass and volume
Atom- smallest unit of an element that
keeps the properties of element
Element- pure substance made of only one
type of atom
Compound- substance made of 2 or more
types of atoms that are chemically bonded
Molecule- type of compound in which
bonds are covalent bonds
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Element
◦ Composed of identical atoms
◦ Cannot be made simpler by chemical or
physical means
◦ EX: copper wire, aluminum foil
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Compound
◦ Composed of 2 or more elements in a
fixed ratio that are chemically combined
◦ Able to be separated by chemical means
◦ Properties differ from those of
individual elements
◦ EX: table salt (NaCl)
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Variable combination of 2 or more pure
substances.
◦ Not chemically combined and can be separated
through physical means
Heterogeneous
Homogeneous
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Homogeneous (solutions)
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Very small particles
Particles don’t settle
Appear to be the same throughout
Examples: air, brass, salt water
Heterogeneous
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Medium/large particles
Particles may/may not settle
Not the same throughout
Examples: concrete, cookie dough
Compound
Mixture
One kind of pieceMolecules
More than one kind Molecule or atoms
Making is a
chemical change
Making is a
physical change
Only one kind
Variable composition
MATTER
yes
MIXTURE
yes
Is the composition
uniform?
Homogeneous
Mixture
(solution)
no
Can it be physically
separated?
PURE SUBSTANCE
no
Heterogeneous
Mixture
yes
Can it be chemically
decomposed?
Compound
no
Element
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Characteristic properties of matter are used
to classify substances
Types of Properties:
◦ Extensive Property
 depends on the amount of matter
 Ex: volume, mass
◦ Intensive Property
 does not depend on amount
 Ex: density, boiling/melting point,
ability to conduct heat/electricity
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Examples:
◦ boiling point
intensive
◦ volume
extensive
◦ mass
extensive
◦ density
intensive
◦ conductivity
intensive
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Physical Property
◦ can be observed without changing the identity of
the substance.
◦ Mixtures separated using physical properties
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Chemical Property
◦ describes the ability of a substance to undergo
changes in identity
◦ Chemical reactions are evidence
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Examples:
◦ melting point
physical
◦ flammable
chemical
◦ density
physical
◦ magnetic
physical
◦ tarnishes in air
chemical
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Physical Change
◦ Changes the form of a substance without changing its
identity
◦ Properties remain the same
◦ Phase changes, dissolving, cutting, bending, etc
◦ Mixtures separated with a variety of techniques (filtering,
evaporation, boiling, etc)
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Chemical Change
◦ Changes the identity of a substance
◦ Products have different properties
◦ Combustion, production of odors, gases, light, rusting,
precipitation, cooking,etc
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Reactants – The substances that react in a
chemical change (stuff you start with)
Products – The substances that are formed by
the chemical change (what you make).
NEW PROPERTIES
Not easily reversed
reactants
carbon
product
+ oxygen → carbon dioxide
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Signs of a Chemical Change
◦ change in color or odor
◦ formation of a gas
◦ formation of a precipitate (solid)
◦ change in light or heat
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Examples:
◦ rusting iron
chemical
◦ dissolving in water
physical
◦ burning a log
chemical
◦ melting ice
physical
◦ grinding spices
physical
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Exothermic Reaction- reaction that gives
off energy (feels warm on outside)
Endothermic Reaction- reaction that
uses up energy (feels cold on outside)
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Energy is always involved when physical or
chemical changes occur.
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Energy can be in various forms.
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Law of Conservation of Energy.
◦ heat
◦ light
◦ Energy can be absorbed or released in a
change, it is not destroyed or created.
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Solids
◦ very low KE - particles vibrate but can’t
move around
◦ fixed shape
◦ fixed volume
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Liquids
◦ low KE - particles can move around but
are still close together
◦ variable shape
◦ fixed volume
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Gases
◦ high KE - particles can separate and
move throughout container
◦ variable shape
◦ variable volume
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Plasma
◦ very high KE - particles collide with enough
energy to break into charged particles (+/-)
◦ gas-like, variable shape & volume
◦ stars, fluorescent light bulbs, CRTs
◦ Particles of matter are always in motion.
◦ As temperature increases, so does speed (Kinetic
Energy) of particles
◦ KMT evidence exists in the presence of the four states
of matter
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Changing from any state to another state
involves the addition or removal of energy
from the system
Melting, freezing, vaporizing, evaporation,
boiling, sublimation, condensation
Condense
Freeze
Evaporate
Melt
Solid
Liquid
Gas
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Groups (aka: families)
◦ vertical columns
◦ numbered 118
◦ have similar chemical properties
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Periods
◦ horizontal rows
◦ properties changes consistently across a period
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Metals
◦ an element that is a good
conductor of electricity
◦ at room temperature, most are
solids
◦ malleable- can be rolled or
hammered into sheets
◦ ductile- can be made into wire
◦ high tensile strength- can
resist breakage when pulled
◦ most have silvery or grayish
white luster
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Nonmetals
◦ an element that is a poor conductor of heat and
electricity
◦ many are gases at room temperature
◦ some are solids: usually brittle, not malleable
Various nonmetal elements
(a) carbon, (b) sulfur, (c) phosphorus, and (d) iodine
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Metalloids
◦ an element that has some characteristics of
metals and nonmetals
◦ appear along staricase line
◦ B, Si, Ge, As, Sb, Te
◦ all are solids at room temperature
◦ less malleable than metals but less brittle than
nonmetals
◦ are semiconductors
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Noble Gases
◦ generally unreactive gases
◦ in far right column of periodic table