matter, its properties components

8/13/2019 Matter, Its Properties Components

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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.

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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

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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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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


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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


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.


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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


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Temperature

is a measure of the intensityof heat in a body

3 common temperature

scales - all use water as areference


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Accuracy

how closely measured values agree with the correctvalue

Precision

how closely individual measurements agree with

each other


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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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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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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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.


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


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.


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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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.


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.


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
http://media/02M11AN1.MOV


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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

matter, its properties components

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