Download Early View of the Elements Democritus Metallurgy

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Chemsitry
Chemsitry)) – Section 2.1
Science 9 – Unit B ((Chemsitry
Early View of the Elements
Ancient Greeks believed all matter was made of 4
elements called Earth, Air, Water and Fire
They thought properties like heat, dryness, cold,
and moisture could be explained by this
Evolving Theories of Matter
Democritus
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Science 9 – Unit B (Chemistry) – Section 2.1
Metallurgy
A Greek named Democritus believed otherwise,
and many agreed with him
“Chemistry” came from khemeia: Greek for “juice
of a plant”
Democritus believed:
Between 6000 and 1000 B.C.E., valuable metals
such as gold and copper were made by metallurgy
1) matter could be broken down into indivisible
bits called atomos: modern-day “atoms”
2) different atoms made different materials
3) combining different atoms made new materials
Science 9 – Unit B (Chemistry) – Section 2.1
Early Metallurgy involved smelting, in which
pure metals are extracted from ores (containing
metal compounds) using high heat
Gold was one of the first metals to be extracted,
followed by copper, silver, lead and tin
Science 9 – Unit B (Chemistry) – Section 2.1
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Metallurgy
Alchemy
Gold is valuable, because it is flexible (easy to work
with) and does not oxidize easily (stays shiny)
Alchemists tried to make gold out of other
materials, but were unsuccessful (sadly)
Raw copper is brittle but can be annealed
(heated) to make it strong and malleable; this
made excellent tools, pots and weapons!
They were not scientists, but they:
developed common glassware like beakers,
flasks and filters
The Iron Age started by extracting iron from rocks
and smelting it into pots and swords
invented plaster of Paris
When first discovered, mercury was called
“quicksilver” after its lustre and liquid state
invented distillation and a technique of making
common mineral acids
wrote Alchemia, the first chemistry textbook
From Bacon to Boyle
Science 9 – Unit B (Chemistry) – Section 2.1
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Science 9 – Unit B (Chemistry) – Section 2.1
Lavoisier
In the 16th century, Sir Francis Bacon wrote a book
arguing that the foundation of science should be
experimental evidence
Lavoisier continued their work by defining an
element as a pure substance that cannot be broken
down (decomposed) further
Boyle (17th century) suggested two things:
He identified 23 of the modern elements this way
1) The purpose of chemistry is to determine what
all materials are made of
Lavoisier also performed many chemical reactions
2) Individual elements could be combined to form
compounds
He measured masses of reactants (going in) and
products (coming out) very carefully
Bacon and Boyle rocked the scientific community
Science 9 – Unit B (Chemistry) – Section 2.1
He developed the Law of Conservation of Mass
Science 9 – Unit B (Chemistry) – Section 2.1
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Law of Conservation of Mass:
In a chemical change, the total mass of the new
substances is always the same as the total mass
of the original substances
So, all the atoms that went into the reaction come
out, but get rearranged into new substances
Matter is neither created nor destroyed, but only
changes form!
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Lavoisier
Law of Definite Composition:
Compounds are pure substances that contain
two or more elements combined together in
fixed (or definite) proportions
This relationship allows compounds to form
ex. every molecule of H2O is made of 2 atoms of
hydrogen (H) and 1 atom of oxygen (O)
Dalton revived Democritus’ ideas and came up
with his “billiard ball” model:
Science 9 – Unit B (Chemistry) – Section 2.1
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Science 9 – Unit B (Chemistry) – Section 2.1
Dalton and Atomic Theory
Law of Definite Composition
Dalton and Atomic Theory
Dalton revived Democritus’ ideas and came up
with his “billiard ball” model:
1) All matter is made up of small particles called
atoms (atoms are solid spheres, nothing inside)
4) Atoms of one element are different in mass and
size from the atoms of other elements
2) Atoms cannot be created, destroyed, or divided
into smaller particles
5) Compounds are created when atoms of
different elements link together in definite
proportions
3) All atoms of the same element are identical in
mass or size
Science 9 – Unit B (Chemistry) – Section 2.1
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Development of Atomic Theory
Development of Atomic Theory
Dalton was incorrect about one thing: atoms can
now be divided into smaller particles!
J.J. Thomson used special gas discharge tubes to
determine that a smaller particle (electron) existed
But…at the time, he was correct
The electron is a “smaller particle” of an atom
His work was a pivotal stage in the development
of the model of the atom
So many scientists contributed at least one idea to
the framework of modern atomic theory
This is the spirit of science at its best!
Development of Atomic Theory
Thomson posited that the
atom was a giant sphere of
positive (+) charge with
negatively-charge (-)
electrons embedded
throughout
He called this the “plum
pudding” model, where the
atom has areas of positive
and negative charge
Science 9 – Unit B (Chemistry) – Section 2.1
Science 9 – Unit B (Chemistry) – Section 2.1
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Science 9 – Unit B (Chemistry) – Section 2.1
Development of Atomic Theory
Ernest Rutherford believed
that if you fired radiation at
an atom, it would bounce
right back to the source
What he discovered is that
radiation will scatter in
many different directions
by the electrons, and backscatter off the center!
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Rutherford added the following to atomic theory:
1) Nearly all the atom’s mass is in a central
nucleus
2) Most of an atom’s volume is empty space
3) Electrons surround the nucleus
4) The positive charge comes from protons in
the nucleus
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Development of Atomic Theory
Development of Atomic Theory
This “solar system”
model of the atom
changed to look like the
diagram on the right
Chadwick
discovered the
neutron as the
second particle in
the nucleus
5) There must be a second particle in the nucleus
Development of Atomic Theory
Niels Bohr refined
the atomic model
to explain more of
the properties of
the atom
Science 9 – Unit B (Chemistry) – Section 2.1
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Science 9 – Unit B (Chemistry) – Section 2.1
Development of Atomic Theory
The exact location of an electron may not be
determined, but the energy of each shell may be
predicted or measured
The work of scientists like de Broglie and
Schrodinger has led to the quantum cloud view of
the atom (the quantum mechanical model)
He arranged the
electrons into
different orbits
called “electron
shells”
In it, we know the chances of finding an electron in
one area of the atom (a cloud of probability)
Science 9 – Unit B (Chemistry) – Section 2.1
Science 9 – Unit B (Chemistry) – Section 2.1
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