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The Amazing Atom!
Dalton's Atomic Theory
Mr. Kneidl Chemistry
Malcolm X Shabazz High School
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John Dalton Dalton believed that
all things were made
of atoms. Though
the idea was
proposed thousands
of years earlier,
Dalton used science
to back up his ideas.This makes it one of
the most important
theories in all of
science.
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The Three Laws
Dalton didn't design his theory all by himself. He
did however note three things that led him to be
able to write a scientific theory about the existence
of atoms.
The Law of Conservations of Mass
The Law of Definite Proportions
The Law of Multiple Proportions
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The Law of Conservation of
Mass
Mass is neither destroyed nor
created during ordinarychemical reactions.
Meaning: The mass you start with willALWAYS equal the mass you end up with.
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The Law of Conservation of
Mass
45 H2O? H2O
Hi h
vo ta e
Before reaction
e ectrodes
ass
cha ber
5.0 H2
80 O2
300 ( ass
of cha ber)
+385 tota
H2O2
Hi h
vo ta e
fter reaction
0 H2
40 O2
300 ( ass
of cha ber)
+
385 tota
O2
H2O
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The Law of Definite
ProportionsThe fact that a chemical compound
contains the same elements in exactly
the same proportions by massregardless of the size of the sample or
source of the compound.
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The Law of Definite
ProportionsHuh?
Water will always be 1 gram of Hydrogento 8 grams of Oxygen
Copper Carbonate will always have thesame proportions
+ +
103 g of
opper arbonate
53 g of
opper40 g of oxygen 10 g of arbon
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The Law of Multiple
ProportionsIf two elements form more than onecompound, the ratio of the second
element that combines with 1 gram ofthe first element in each is a simplewhole number.
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The Law of Multiple
ProportionsHuh?
An example. Water and HydrogenPeroxide. Both are made of water and
hydrogen.
H2O & H2O2
water hydrogen peroxide
Ratio of oxygen is 1:2 (an exact ratio)
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The Law of Multiple
Proportions Water is 8 grams of oxygen per gram ofhydrogen.
Hydrogen peroxide is 16 grams of oxygen
per gram of hydrogen. 16 g to 8 g is a 2:1 ratio
Of course! You need to add a whole atom,
you cant add a piece of an atom.
How Fancy.
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Re ap
Dalton crafted his theory on atoms
because of three known laws.
The Law of Conservation of Mass
The Law of Definite Proportions
The Law of Multiple Proportions
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Dalton's Atomi Theory
Dalton stated that elementsconsisted of tiny particles calledatoms
He also called the elementspure substances because allatoms of an element wereidentical and that in particularthey had the same mass.
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Dalton's Atomi Theory
All matter is composed of extremely small particles calledatoms which cannot be subdivided, created, or destroyed.
Atoms of a given element are identical in their physical andchemical properties.
Atoms of different elements differ in their physical andchemical properties.
Atoms of different elements combine in simple, wholenumber ratios to form compounds.
In chemical reactions, atoms are combined, separated, orrearranged but never created, destroyed, or changed.
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Homework
As you can see, Dalton has principles to his theory. We saidbefore that he based his theory primarily on three laws. The lawof conservation of mass, the law of definite proportions, and thelaw of multiple proportions.
Your assignment is to relate the principles of Dalton's theory to thethree laws or other ideas by older scientists. Some theories maybe used more than once, but all theories must be used at somepoint. This assignment is due by next class and you may work onthis assignment until the bell rings.
Hooray!
