matter, its properties components
TRANSCRIPT
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The Foundations
of Chemistry
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Principles of General Chemistry, 2nded. by M. Silberberg
Chemistry, 8th ed.by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley.
2
Fundamental Definitions
States of Matter Chemical and Physical Properties
Chemical and Physical Changes
Measurements in Chemistry: Units andConversion, Dimensional Analysis
Daltons Atomic Theory
Laws of Mass Conservation, of DefiniteComposition, and of Multiple Proportions
Components of Matter: Elements, Compoundsand Mixtures
Lecture Outline
3
Chemistryis the study of matter
its properties, the
changes it undergoes,
and the energychanges
that accompany those
processes
is the central and
fundamental science
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Matteranything that has
mass and occupiesspace
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States of Matter
Classical:
Solids
Liquids
Gases
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States of Matter
Non-classical:
Plasma Bose-Einstein
Condensate
Liquid Crystals
Supercritical
fluids
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Properties of Matter
Physical Properties
those which the substance shows by itselfwithout interacting with another substance
e.g. density, color, length
Chemical Propertiesthose which the substance shows as itinteracts with, or transforms into, othersubstance
e.g. reactivity, f lammability
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Properties of Matter
Extensive Propertiesamount dependent
properties
e.g. mass, volume, energy
Intensive Propertiesamount independent
propertiese.g. temperature, density
can be used to differentiate substances
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Changes in Matter
Physical Changes
occurs when asubstance alters
its physical form,not its
composition
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Changes in Matter
Physical Changes
frost formation as thetemperature drops on a humid
winter night
perspiration evaporateswhen you relax after
jogging
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Changes in Matter
Chemical Changes= Chemical Reaction
occurs when a substance is converted into adifferent substance
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Changes in Matter
Chemical Changes
a match ignites to formash and a mixture of
gases
a silver fork tarnishes
slowly in air
a cornstalk grows from aseed that is watered and
fertilized
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Energy (in the study of matter)
Energyability to do work
is conserved: may be converted from one formto the other , but is not destroyed
e.g. two electrically charged particles
potential energy gained when the charges are separated isconverted to kinetic energy as the attraction pulls themtogether
e.g. a fuel and its waste product
as the fuel burns, its potential energy is converted to thekinetic energy of the moving car
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Use of Numbers
Significant figures
digits believed to be correct by the personmaking the measurement
Exact numbers have an infinite number ofsignificant figures
12.000000000000000 = 1 dozen
Measurements in Chemistry
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Measurements in Chemistry
Quantity Unit Symbol
length meter m
mass kilogram kg
time second s
current ampere A
temperature Kelvin K
amt. substance mole mol
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Metric Prefixes
Name Symbol Multiplier mega M 106
kilo k 103
deka da 10 deci d 10-1
centi c 10-2
milli m 10-3
micro 10-6
nano n 10-9
pico p 10-12
femto f 10-15
Measurements in Chemistry
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Common Conversion Factors:
Length
1 m = 39.37 inches
2.54 cm = 1 inch
Volume
1 liter = 1.06 qt
1 qt = 0.946 liter
Measurements in Chemistry
Pressure
1 atm = 760 torr
1 atm = 760 mmHg
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The Unit Factor Method DIMENSIONAL ANALYSIS
Simple but important method to get correct
answers in word problems.
Method to change from one set of units to
another.
Measurements in Chemistry
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Problem: Lithium (Li) is a soft, gray solid that has the lowestdensity of any metal. If a slab of Li weighs 1.49 x 103mg and has
sides that measure 20.9 mm by 11.1 mm by 11.9 mm, what is thedensity of Li in g/cm3?
1 mg
10-3 g= 1.49 g1.49 x 10
3 mg x
20.9 mm x10 mm
1 cm= 2.09 cm
Similarly the other sides will be 1.11 cm and 1.19 cm, respectively.
2.09 x 1.11 x 1.20 = 2.76 cm3
Density of Li =1.49 g
2.76 cm3= 0.540 g/cm3
Measurements in Chemistry
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Temperature
is a measure of the intensityof heat in a body
3 common temperature
scales - all use water as areference
Measurements in Chemistry
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Accuracy
how closely measured values agree with the correctvalue
Precision
how closely individual measurements agree with
each other
Measurements in Chemistry
The Componentsof Matter
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Principles of General Chemistry, 2nded. By M. Silberberg
Chemistry, 8th ed.by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley.
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A Molecular View:Daltons Atomic Theory
1) An element is composed of extremely
small indivisible particles called atoms.
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A Molecular View:Daltons Atomic Theory
2) Atoms cannot be converted or transformed
into atoms of another element.
3) All atoms of a given element have identical
properties, which differ from those of
other elements.
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A Molecular View:
Daltons Atomic Theory
4) Compounds are formed when atoms of
different elements combine with each
other in small whole-number ratios.
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Components of Matter
Element- the simplest type of substance with
unique physical and chemical properties
-consists of only one type of atom
- cannot be broken down into any simpler substances
by physical or chemical means
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Components of Matter
Substancematter whose composition is fixed
Moleculea structure that consists of two or
more atoms that are chemically bound together and
thus behaves as an independent unit.
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Components of Matter
Compound- a substance
composed of two or more
elements which are chemically
combined.
Mixture- a group of two or
more substances and/orcompounds that are physically
intermingled.
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Components of Matter
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Components of Matter
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Mass Laws
Law of Conservation of Mass
there is no detectable change in the mass during achemical change
total mass of substances do not change after thereaction
total mass total mass=
CaO + CO2 CaCO3
56.08 g + 44.01 g 100.09 g
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Mass Laws
Law of Definite Composition
no matter the source, a particular compound iscomposed of the same elements in the same
parts (fractions) by mass
e.g. Calcium carbonate
Analysis by Mass(grams/20.0 g)
Mass Fraction(parts/1.00 part)
Percent by Mass(parts/100 parts)
8.0 g calcium2.4 g carbon9.6 g oxygen
20.0 g
40% calcium12% carbon48% oxygen
100% by mass
0.40 calcium0.12 carbon0.48 oxygen
1.00 part by mass
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Mass Laws
Law of Multiple Proportions
if elements A and B react to form two
compounds, the different masses of B
that combine with a fixed mass of A can
be expressed as a ratio of small whole
numbers
e.g. given nitrogen and oxygen (N and O)
compounds that may be formed: NO, N2O, NO2
Fundamental Particles
Particle Mass (amu) Charge
Electron (e-) 0.00054858 -1
Proton (p,p+) 1.0073 +1
Neutron(n,n0) 1.0087 0
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The Discovery of Electrons
Humphrey Davyin the early1800s passed electricity through
compounds and noted: that the compounds decomposed into
elements.
concluded that compounds are heldtogether by electrical forces.
Michael Faradayin 1832-1833realized that the amount of reaction thatoccurs during electrolysis is proportional tothe electrical current passed through thecompounds.
Cathode Ray Tubesexperiments performed in the
late 1800s & early 1900s.
Consist of two electrodes sealed in a glass tube containing agas at very low pressure.
When a voltage is applied to the cathodes a glow dischargeis emitted.
The Discovery of Electrons
These rays are emitted from cathode (- end)
and travel to anode (+ end).
Cathode Rays must be negatively charged!
J.J. Thomsonmodified the cathode ray tube
experiments in 1897 by adding two adjustable
voltage electrodes. Studied the amount that the cathode ray beam was
deflected by additional electric field.
The Discovery of Electrons The Discovery of Electrons
The Discovery of Electrons
Thomson used his modification to measure the chargeto mass ratio of electrons.
Charge to mass ratio
e/m = -1.75881 x 108coulomb/g of e-
Thomson named the cathode rays as electrons.
Thomson is considered to be the discoverer ofelectrons.
TV sets and computer screens are cathode ray tubes.
The Discovery of Electrons
Robert A. Millikanwon the 1stAmerican NobelPrize in 1923 for his famous oil-drop experiment.
In 1909 Millikan determined the charge and mass ofthe electron.
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The Discovery of Electrons
Millikan determined that the charge on a single
electron = -1.60218 x 10-19coulomb.
Using Thomsons charge to mass ratio we get
that the mass of one electron is 9.11 x 10-28g.
e/m = -1.75881 x 108coulomb
e = -1.60218 x 10-19coulomb
Thus m = 9.10940 x 10-28g
Eugene Goldstein noted streams of positively chargedparticles in cathode rays in 1886.
Particles move in opposite direction of cathode rays. Called Canal Rays because they passed through holes
(channels or canals) drilled through the negative electrode.
Canal rays must be positive.
Goldstein postulated the existence of a positivefundamental particle called the proton.
The Discovery of Protons
Rutherford and the Nuclear Atom
Ernest Rutherford directed Hans Geiger and Ernst
Marsdens experiment in 1910.
- particle scattering from thin Au foils= the basic picture of the atoms structure.
Rutherford and the Nuclear Atom
Rutherfords major conclusions from the
-particle scattering experiment
1. The atom is mostly empty space.
2. It contains a very small, densecenter called the nucleus.
3. Nearly all of the atoms mass isin the nucleus.
4. The nuclear diameter is 1/10,000
to 1/100,000 times less than
atoms radius.
Rutherford and the Nuclear Atom
James Chadwick in 1932 analyzed the
results of -particle scattering on thinBe films.
Chadwick recognized existence of
massive neutral particles which he
called neutrons.
Chadwick discovered the neutron.
The Discovery of Neutrons
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General features of the atom today Atomic Symbols
X= atomic symbol of the element
A = mass number; A = Z + N
Isotopes = atoms of an element with the samenumber of protons, but a different number
of neutrons
AZ
Z = atomic number(the number of protons in the nucleus)
N = number of neutrons in the nucleus
X The Symbol of the Atom or Isotope
Atomic Number
is equal to the number of protonsin the nucleus.
Sometimes given the symbol Z.
In 1913 H.G.J. Moseley realizedthat the atomic numberdetermines the element .
The number of electrons in aneutral atom is also equal to theatomic number.
Mass Number and Isotopes
Mass numberis given the symbol A.
is the sum of the number of protons and neutrons.
Isotopesare atoms of the same element but with
different neutron numbers. example of an isotopic series is the hydrogen isotopes:
1H, 2H and 3H
Mass Number and Isotopes
PROBLEM: Silicon (Si) is essential to the computer industry as a majorcomponent of semiconductor chips. It has three naturally
occurring isotopes: 28Si, 29Si, and 30Si. Determine the number
of protons, neutrons, and electrons in each silicon isotope.
SOLUTION: The atomic number of silicon is 14. Therefore,28Si has 14p+, 14e-and 14n0(28 - 14)
29Si has 14p+, 14e-and 15n0(29 - 14)
30Si has 14p+, 14e-and 16n0(30 - 14)
Calculating the Atomic Mass of an Element
PROBLEM: Silver (Ag: Z = 47) has 46 known isotopes, but only two occur
naturally, 107Ag and 109Ag. Given the following mass
spectrometric data, calculate the atomic mass of Ag:
Isotope Mass (amu)
Abundance (%)
107Ag
109Ag
106.90509
108.90476
51.84
48.16
SOLUTION:
mass portion from 107Ag = 106.90509 amu x 0.5184 = 55.42 amu
mass portion from 109Ag = 108.90476 amu x 0.4816 = 52.45 amu
atomic mass of Ag = 55.42 amu + 52.45 amu = 107.87 amu
atomic mass of Ag = (Mass1)(%abundance1) + (Mass2)(%abundance2)
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questions?
It is impossible for a man tolearn what he thinks healready knows Epictetus