Transcript Chemistry - hrscience9

A look back through history
UGGH…GA UGGH!
(translation: I am the first
chemist ever…I have made
fire and will be featured in
chemistry textbooks for
years to come…uggh!)
Prior to 8000 BC a period of
time known as the Stone
Age, humans only had the
knowledge to use stone
tools. Upon the discovery of
fire, fire was used to cook
food, fire-harden mud bricks
and to make tougher tools.
Early chemists were mostly
concerned with materials that had
high value to humans. This included
metals such as gold and copper.
Further investigation lead to the
discovery of the different properties
of copper when heated. Copper
was no longer brittle (easily
broken), but was soft and
malleable. Around 4500 BC, the
discovery of combining metals such
as copper and tin produced a strong
and hard material called bronze.
Around 1200 BC a group of
people known as the Hittites
discovered how to extract iron
from rocks and turn it into a
useful material. This began the
Iron Age. The extension of this
was the creation of steel which
was produced when carbon was
added to iron. Discoveries were
often as a result of trying to
produce better and stronger
weaponry.
Democritus – 460 – 360 BCE
Around 500 BC there were two
versions of the composition of
matter. The most believed was
the view of Aristotle that
everything was made of earth,
air, fire, and water. A more
accurate view, but less popular
was the view of Democritus
that everything was made up of
different types of atomos.
Atomos was the smallest a
particle could be broken down
into.
Until the 1500s individuals
known as alchemists continued
to conduct experiments,
although not to further the
understanding of matter, but
rather in a search for ways to
make gold from other metals.
Although not successful, these
alchemists developed many
chemistry tools and
inadvertently made many
practical discoveries.
Not until the late 1500’s did we
begin to see people engaged in
activities more like the scientists of
today. In the 1660’s Robert Boyle,
an Irish scientist experimented on
gases under pressure and believed
that Democritus’ theories regarding
particles was accurate. He believed
there were particles of different
shapes and sizes that would group
together in a variety of ways to
make different substances.
In the 1770’s Antoine Laurent
Lavoisier, a French scientist,
studied chemical
interactions. By the 1780’s,
he had developed a system
for naming chemicals. This
system standardized the
language used and allowed
all scientists communicate
their ideas in a way that was
more easily understood.
In 1808, John Dalton developed
his own theory of the
composition of matter. He
suggested that matter was
made up of elements. He was
the first to define an element as
a pure substance that contained
no other substances. Dalton
also put forth the first modern
theory of atomic structure. He
believed that each element was
made of particles called atoms
and that each element had its
own kind of atom. His model is
sometimes called the “billiard
ball model” because he thought
of the tiny atoms as solid
spheres.
JJ Thomson is credited with
being the first person to
discover a subatomic
particle. He showed that
negatively charged particles
found in beams of light like
the one seen in the picture.
The particles were called
electrons.
In 1897, Thomson described the
“Raisin Bun” model of the
atom. In this model, the atom
is a positively charged sphere
with negatively charged
electrons contained within it.
In 1904, Hantaro Nagaoka,
refined the model by suggesting
that the negatively charged
electrons actually surrounded
the atom like a planet orbiting
the sun.
British scientist Ernest
Rutherford conducted research
at McGill University which is in
Montreal. He discovered that
the atom has a nucleus at its
core. This was discovered by
sending high speed particles at
thin gold foil. Most of the
particles went straight through,
others were deflected,
however.
Niels Bohr of Denmark,
suggested that the electrons
orbiting a atom do not do so
randomly. Rather, the move
in circular orbits he call
electron shells. He believed
that electrons jump between
these shells by gaining or
losing energy.