Alexander the great

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Alexander the great
BUCEPHALUS
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• The horse was quite wild and none could ride it.
  Alexander watched the horse's behavior and
  quickly realized that it was scared by the
  movements of the potential rider's shadow. He
  took the horse and turned it's face towards the
  sun so that it couldn't see his shadow, and
  quickly rided it. After that incident Philip gave
  the horse to his son and he said to him
• "...Son, find another kingdom to rule because
  Macedonia is too small for you!..."

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   Alexander The Great (356 323B.C.)
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Homework

• Read pages 260 to 274
• Do problems 1-10 274

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We have been talking about physical aspects of
individual chemicals and how them make both ionic
and covalent compoundsbut how do they interact
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The chemical equation represents what is going on
in the chemical reaction and designations in the
chemical equation tell us what is going on
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Chemical equation
H2 O2 ? H2O energy
product
reactants
Arrow
Diatomic state of H2 and O2
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Equations can also include the physical state of
the reactants and products.

• HC2H3O2 NaHCO3 ?
• CO2 NaC2H3 H2O

By adding the symbols to our equation ?(S) (l)
(g) (aq) we can more accurately see what's going
on.
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HC2H3O2 NaHCO3 ? CO2 NaC2H3 H2O

• HC2H3O2(aq) NaHCO3(s) ?
• CO2(g) NaC2H3(aq)H2O(l)

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Reactions do not just flow in one direction and
not all reactions stop with the creation of
products

• rocket engine H2 O2 ?H2O energy

H2O will dissociate into H2 and O2 if it is acted
upon by energy
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We specificy the environment of the reaction
Do the conditions matter in a chemical rxn
a elec. b water c heat etc.
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This is an example from your book
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The chemical equation is predicated on the Law
of Conservation of Mass

• Matter is neither created
• or
• Destroyed

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Law of Conservation of Mass
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C O2 ? CO2

• Put a flag on the carbon

They can actually do that
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when we light a candle in a closed vessel the
candle uses up all the air??Did the air get
used up

• Remember conservation of mass law

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To track the elements so you can know where the
ingredients go

• Set up an equation

equal the products
all the reactants
? H2O
H2 O2
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According to the law (not theory or hope) law of
conservation of matter both sides of the
equation must equal one another or in the
language of chemistry both sides of the
equation must Balance.
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To check to see if the equation is balanced you
compare the

• elements on the reactant side

to the elements on the product side
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• H2 O2 ? H2O

We know they werent used up
by placing a coefficient in front of the
substance we need to increase
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Remember that ionic compounds must be balanced on
a compound level and then the entire equation
must be balanced

• Na Cl2 ? NaCl

Al O2 ? Al2O3
4Al 3O2 ? 2Al2O3
2Na Cl2 ? 2NaCl
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These balancing numbers in front of the elements
in an equation is called the coefficient.

• We can not change the subscripts or that will
  change the reactants and products themselves

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Law of Conservation of Mass is the basis for
balancing equations
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Increase the substances on either the reactant
side or product side until both sides have an
equal number of components.
You cant increase parts of substances only
complete substances
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Balancing chemical equations is important because
by doing so we can

• 1) accurately determine the ratio of reactants
  to products
• 2) account for each element involved.

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Balancing equations without getting too crazy

• A write down the reactants and products
• B first balance the metals
• C then balance the nonmetals
• D then balance the hydrogen and oxygen
• E lowest common denominator
•  Use the T grid to keeping track of values.

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Start with the equation hydrogen oxygen ? water
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Air scoop
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CH4 O2 ? CO2 H2O
C2H4 O2 ? H2O CO2
Na Cl2 ? NaCl
Zinc and hydrochloric acid (HCl) produces
zinc(II) chloride and hydrogen gas write a
balanced equation .
Zn HCl ?ZnCl2 H2
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solid Calcium metal reacts with water to from
aqueous calcium hydroxide and hydrogen gas
Ca H2O ? Ca(OH) 2 H2

• Copper(II) oxide reacts with powdered aluminum to
  produce molten copper and aluminum oxide in a
  wild reaction. Write and balance the equation

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solid potassium chlorate decomposed to form
potassium chloride and oxygen gas

• KClO3 ? KCl O2

NH3 O2 ? NO2 H2O
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K Br2 ? KBr

• SO2 O2 ?SO3

H2SO4 BaCl2 ? BaSO4 HCl
Potassium Bromide ? Potassium bromide
2 K Br2? 2KBr