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Studying All That Matters
I thought that I would never see a class as hard as chemistryWith all the thoughts that chemists had, I‘m sure that they
were driven mad!
But oh, the things I‘ve slowly learned—from halogens to oil burned.
At first the periodic table seemed quite a task; I was not able!It was too much, and I confess—when exam time came, I blew
the test.
But as I learned, the more I saw that chemistry explains it all.Why make-up runs! Why acid rain! How toast is burnt! Why
plugged up drain!How iron rusts and sodas fizz! I know so much—I‘m now a
whiz!So I will sing its praises true. Oh, chemistry, how I love you!
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Classification of Matter
Matter is anything that has mass (inertia) and occupies space.
Heterogeneous matter – different parts have different properties
Homogeneous matter – has similar consistency throughout
Homogeneous mixtures – solutions
Pure substances – compounds and elements
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Dalton’s Atomic Theory
All elements are composed of tiny indivisible particles called atoms NWK: atoms are divisible
All matter is composed of combinations of these atoms
Atoms of the same element are identical and atoms of different elements are different NWK: isotopes of the same element are
different
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A POEM
Matter, matter everywhere,
But what are we to think?
What it is all composed of,
Is essentially the link!
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Models of the Atom
Chocolate-Chip Ice Cream Model Also called plum pudding model – J. J. Thompson Ice cream is the proton sea chips are electrons
Rutherford Model (Thompson‘s student) Atom mostly empty space – nucleus in center and
electrons in orbit
Bohr Model Electrons orbit in shells, do not have to stay in the same
shell all the time (move up/down and absorb/give off energy)
Quantum Mechanical Model Mathematical model based on probability of where
electrons are at any given time Electrons within shells behave differently (have s, p, d
orbitals)
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Parts of the Atom
Protons – positively charged (+) Determine how atom will behave (because number
of protons never changes) Atomic number = number of protons Found in nucleus
Neutrons – no charge Found in nucleus Weigh about the same as protons Different amounts indicate different isomers (some
isotopes are radioactive, some are not)
Electrons – negatively charged (-1) Tiny (weigh only 1/1860th of proton) Orbit nucleus May be lost or gained when elements combine
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ANOTHER POEM
To smash the simple atom
All mankind was intent.
Now any day, the atom may
Return the compliment!Odgen Nash
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Three Groups of Elements
Metals – Na, Ca, Fe, Co, Ag Have luster, conduct electricity and heat, are
ductile and malleable Have 1-3 electrons in their outer shells Form ionic bonds
Nonmetals – C, I, Cl, O Do not shine, do not conduct electricity or heat,
are not ductile or malleable Have 5-8 electrons in their outer shells Form covalent bonds
Metalloids – As, Ge Si Usually have 4 electronic in their outer shells, or
on ―line‖ between metals and nonmetals Have some properties of metals and of nonmetals
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Compounds
Compounds are substances composed of two or more elements
Examples: NaCl, water (H2O)
They are combined in definite proportions
They have definite composition
They cannot be separated by physical means
They can be separated by chemical means
4 million compounds have been reported
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Chemical Bonding
Outer shell electrons play an important role in bonding Goal is to maximize stability via perfect outside
shell (like Nobel Gases)
8 electrons in outer shell is extremely stable.
Elements may share or transfer electrons Ionic bonds – transfer of electrons, occurs
between metal (or hydrogen) and nonmetal
Covalent bonds – sharing of electrons, occurs between two nonmetals
Basis of live (all carbon compounds are covalently bonded)
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ODE TO CARBON
(A POEM BY ANOTHER NAME)
What is carbon? You may ask. To tell you is no easy task.
Carbon is in most compounds. Her combinations have no bounds.
Carbon is a lump of coal, dug out of a miner’s hole.
A diamond carbon also is—a stone that is more hers than his.
Carbon as a fossil fuel is even more a precious jewel.
As hydrocarbon, she’s the gas that make our cars go extra fast.
Branching, bonding, even chains, dating isotopes in it’s range.
Multiple uses combined and free. Her value is no mystery!
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Other Chemical Bonds
Metallic bonds Form when overflow electrons leave their atoms and
wander freely throughout metal Can be one element, like Fe, Al, or C Or a mixture of elements
Brass (Cu and Zn) and bronze (Cu and Sn)
van der Waals bonds Cohesive forces
when there is a weak atraction of atom A‘s nucleus (+) with atom B‘s electrons (-)
Examples are candle wax, talcom powder, and hydrogen bonds When hydrogen bonds, it‘s lone electron is shifted
and the exposed positive nucleus is weakly attracted by other electrons
happens in water and makes it a good solvent
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The Three (Four) States of Matter
An ice cream soda contains all three states of matter: solid, liquid, gas
Transition from one state to another requires energy (melting, boiling, solidification, sublimation)
The ―fourth‖ state of matter is plasma Most common state in universe (stars)
Requires extremely high temperatures
Gases take on different character
Electrons are striped off atoms (just a few, as in fluorescent light, or completely, as in stars)
Exhibit properties not common to gases (conduct electricity and can be confined in magnetic fields)
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A VERY LOVELY POEM
Solid is the chair on which I sit.Liquid is the tea on which I sip.
But gases—these are the most difficult of them all.Tiny elements freely float about, plagued by loneliness.
Shy ones drift round in dazed pursuit,longing for the perfect other—not driven to mingle.
Others are bold.Eagerly introducing themselves, pompous and flaunting,
They are considered to be ungenial and abrasiveby the more conservative crew.
Hovering, they soundlessly shiveras a small explosion discharges within a glass beaker
before the chalkboard.Judy Copenbarger
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Physical and Chemical Changes
Physical change – will not alter basic properties of substance
No new substance is formed
Change in shape, size, or state
Why popcorn pops (water in kernel changes state)
Chemical change – new substance is formed with different properties
Requires a chemical reactions
May also result in production of light, heat, gas, color change, or precipitate
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ANOTHER @?!#* POEM
A chemical change is fun to see
I know how to tell if one happens to be!
Exothermic or endothermic—heat absorbed or released
Or the sign of a color change easily policed.
Production of a gas, with bubbles galore
Or the glow of light energy; and there‘s even more!
Sometimes a solid will precipitate out
And that‘s what reactions are all about!
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Chemical and Physical Changes
A new substance coming into existence
A new appearance visible to the human eye
With logic and persistence
The truth behind chemical and
Physical changes we cannot deny.
Grass extending in height
Combining with all underground
Escaping the deadly blight.
A chemical change we have now found
Leaves changing color in fall
Release their hidden hues
Such beauty in them all.
A physical change is what comes to be true
The difference not simply seen
Requires thought and time.
The truth of the complicating two lies between
The obvious and the working mind.
By Sandra Ruiz
http://www.ncrel.org/mands/docs
/6-12.htm
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Types of Chemical Reactions
Composition – two or more substances combine A + B AB Sulfur (car emissions) + oxygen sulfur dioxide, which
causes chronic bronchitis and emphysema
Decomposition – one substance breaks down AB A + B Hydrogen peroxide water + oxygen
Single Replacement – an uncombined element replaces another element in a compound A + BC AC + B Magnesium + hydrochloric acid magnesium chloride +
hydrogen
Double replacement – two compounds exchange ions AB + CD AD + CB Hydrochloric acid + magnesium hydroxide magnesium
chloride + water
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Solutions, Colloids, Suspensions
A solution is a homogeneous mixture
Is not a pure substance
Can be separated by physical means
Has a solute – substance being dissolved; usually the smaller amount
And a solvent – substance doing the dissolving; usually the larger amount
Colloids and suspensions are not true solutions
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Acids, Bases, and Salts
Inorganic compounds can be classified into four broad categories: Acids, bases, salts [and oxides (rust)]
pH is a means of measuring the acid/base strength of solutions (pH expresses the hydrogen ion concentration) pH from 1-6 = acidic, 7 = neutral, 8-14 = basic
―pH balanced‖ means the substances matches the pH of what it is balanced with
Acids, bases, and salts may form electrolytic solutions Conduct electricity because they contain ions
Acids and bases can be distinguished using indicators Indicators – change color in the presence of acids or
bases
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A LITTLE POEM
Little Johnny took a drink
But now he‘ll drink no more
For what he thought was H-2-O
Was H-2-S-O-4!
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A LOVE POEM
Oh my love is like a greenish-yellow gas, Chlorine,That has newly gained an electron;
Oh my love is like a negatively charged ion,That is now named Chloride.
As fair art thou, my attractive gas,So deep in love am I:
That I gave you an electron, my dear,Thus I became positively charged.
Till our attraction gives reaction, my love,To form white solid—table salt;
And I will love thee still, my dear,When our particles are arranged in crystals of sodium chloride.,
And fare thee well, my only love.While the crystal is held together by ionic bond forces,
And I will come again, my love,Tho‘ it were ‗cross an ocean of ten thousand miles.
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AN OLD-FASHIONED LOVE SONG
Just a little atom of chlorine, valence minus one.
Swimming through the sea, diggin' the scene, just havin' fun.
She's not worried about the shape or size of her outer shell.
It's fun to ionize! Just a little atom of chlorine with an unfilled shell.
Somewhere in that sea lurks handsome sodium
With enough electrons on his outside shell plus another one.
"Somewhere in this deep blue sea, there is a negative for my extra energy
Yes, somewhere in this foam, my positive will find a home.”
Then unsuspecting chlorine felt a magnetic pull
She looked down and her outside shell was full!
Sodium cried "What a gas, be my bride,
And I'll change your name from chlorine to chloride!"
Now the sea evaporates to make the clouds for rain and snow,
Leaving her chemical compounds in the absence of H2O
But the crystals that wash upon the shore are happy ones,
So if you never thought before, think of the love that you eat when you salt your meat!
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Matter and Energy
Every substance has a specific amount of energy associated with it
When substances react chemically, they can either lose or gain energy
Chemical reactions are either exothermic (heat-producing) or endothermic (heat-utilizing)
This is because old bonds are broken (requires energy) and new bonds are formed (releases energy)
Law of Conservation of Mass and Energy
The total sum of matter and energy in the universe is always the same (constant)