atomic molecular view of mattert

8/3/2019 Atomic Molecular View of Mattert

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Atoms & Elements


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What is Chemistry?

The study of matter of matter

and its changes


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What does a chemist

do? Chemists analyze substances

Chemists create or synthesize

new substances

Chemists create models and

test the power of theories

Chemists measure the physical

properties of substances


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Areas of chemistry

Analytical chemistry

Organic chemistry

Inorganic chemistry

Physical chemistry

biochemistry


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Careers in chemistry

Quality control chemist

Industrial research chemist

Forensic chemist

Environmental chemist

Sales representative Chemical educator


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Scientific Method

Consists of three parts:

Observation

Explanation through the

creation of a theoretical model

Testing the model


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Observations

A statement(s) that describe

what we see, touch, feel, smell,

or taste (the five senses)


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Conclusion

A statement as to what one

thinks about a series of

observations


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Data

Facts that are learned by

observing some physical,

chemical or biological system


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Scientific Law

A broad generalization, based

on the results of many

experiments Scientific laws are expressed in

terms of mathematical

equations: (Examples: E = mc2,PV = nRT , PV= C)


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Classification of Matter

Matter is anything that has

mass and occupies space

Matter can be classified aselements, compounds, or

mixtures


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Elements

Substances that cannot be

decomposed further by ordinary

chemical means. All elements can be identified

by a chemical symbol


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Elements (cont.)

The first letter is always

capitalized

The second letter (if there isone) is always lowercase


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Compounds

A substance that is composed

of two or more different

elements in which elements arealways combined in a fixed ratio


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Examples of compounds

Carbon dioxide (CO2)

Water (H2O)

Ammonia (NH3)

Glucose (C6H12O6)

Sodium chloride (NaCl)


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Mixtures

Materials that have variable

composition

Two types of mixtures: a)homogeneous

and b) heterogeneous


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Homogeneous Mixtures

Homogeneous mixtures have

properties that are identical

throughout the sample All solutions are considered to

be homogeneous mixtures


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Examples of

homogeneous mixtures Air (a mixture of gases)

Alloys (brass, bronze, sterling

silver, steel)

Rubbing alcohol (isopropyl

alcohol and water)

Saltwater


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Heterogeneous Mixtures

Heterogeneous mixtures

consists of regions (phases)

which are not uniform.


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Examples of

Heterogeneous Mixtures Oil & water

Salads

Soups

Blood

Milk


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Physical and Chemical

Changes Physical change: A change in

which no change in the

composition occurs. No nessubstances are formed

Chemical change: A change in

which the composition of thesubstance is changed


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Examples of physical

changes Ice melting

Water boiling

Dissolving sugar in water

Alcohol changing into a vapor


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Examples of chemical

changes Sugar fermenting into alcohol

Iron rusting

Silver tarnishing

Butter turning rancid


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Properties of Matter

Physical Properties: Properties

which does not involve a

change in chemical composition(Examples: density, melting

point, boiling point, solubility,

malleability, etc.)


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Chemical properties

Properties which describe a

chemical change which takes

place Examples: Sugar decomposes

when heated, iron changes to

rust when exposed to moist air


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Extensive Properties

A property that depends on the

size of the sample

Examples: Volume, mass, andlength


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Intensive properties

Properties that are independent

of sample size


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Examples of Intensive

Properties Color

Melting point

Boiling point

Density

Electrical conductivity


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Intensive properties are better

in identifying than extensive

properties


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States of Matter

Solid: Definite shape & volume

Liquid: Definite volume, but

indefinite shape

Gas: Indefinite shape & volume


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Law of conservation of

mass States that matter cannot be

created nor destroyed

Mass is conserved


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Law of definite

proportions States that in a given chemical

compound, elements are always

combined in the sameproportions by mass


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Daltons Atomic Theory

Matter consists of tiny particles

called atoms Atoms are indestructible

In any sample of a pure

element, all atoms are identicalin terms of mass and otherproperties


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Daltons atomic theory

(cont.) The atoms of different elements

differ in mass and other

properties When atoms of different

combine to form compounds,

new and more complexparticles form


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Law of multiple

proportions Whenever two elements form

more than one compound, the

different masses of one elementthat combine with the same

mass of the other element are

in the ratio of small wholenumbers.


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Law of Multiple

Proportions (cont)

Example: Sulfur can react with

oxygen to form two different

compounds:SO2

SO3


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Subatomic Particles

Consists of protons, neutrons,

and electrons


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Protons possess a positive

charge

Electrons possess a negativecharge

Neutrons possess a neutral (no)

charge


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Protons and neutrons are

located in the nucleus of the

atoms Electrons move about the

nucleus


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Isotopes

Atoms that have the same

number of protons, but different

number of neutrons


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Atomic number & Mass

number

Atomic number : number of

protons

Mass number: number ofprotons & neutrons


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Atomic mass

Weighed average of all isotopes

that compose that element

Units are expressed in atomicmass units (amu) for each atom

Carbon-12 is used as the

standard


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Atomic Mass Unit

Symbolized as u

1/12 the mass of the carbon-12

isotope


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Average atomic masses can be

determined from isotopic

abundances


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The periodic table

Developed by Mendeleev in

1871

His table arranged elementsbased on increasing atomic

mass


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Modern periodic table arrange

elements based on increasing

atomic number


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Horizontal rows are called

periods

Vertical rows are called groupsor families


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Groups & families of

elements

Representative elements:

(Groups IA- VIIIA)

Alkali metals (Group IA) Alkaline earth metals (Group

IIA)

Halogens (Group VIIA)

Noble gases (Group VIIIA)


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Transition elements (B groups)

Inner transition elements

a) lanthanides (58-71)

b) actinides (89-103)


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Characteristics of

Metals

Solid (except Hg)

Exhibit a luster (shiny)

Ductile

Malleable

Good conductors of

heat/electricity


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Characteristics of

nonmetals

Solids, gases, and one liquid

Solids are brittle

Poor conductors ofelectricity/heat

Not malleable

Not ductile


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Metalloids

Possess characteristics

between those of metals and

nonmetals Tend to serve as

semiconductors

Examples: silicon, boron,germanium, tellurium, etc.

atomic molecular view of mattert

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