An example of a physical change
is…
A) melting ice
 B) burning paper
 C) rusting iron
 D) photosynthesis

Ryan watched his mom crack eggs into a frying pan. He
noticed that the transparent liquid surrounding the yolks of
the eggs became solid and white when the pan was placed
over the burner of the stove.

Which of the following statements describes
the changes that occur to the egg during
frying?
– A) the changes are physical because a change in
state occurs and an odour is detected
– B) the changes are chemical because an odour is
detected and heat is released
– C) the changes are physical because a new colour
appears and heat is absorbed
– D) the changes are chemical because heat is
absorbed and a new substance is formed.
Cement and gravel are combined
in specific proportions to produce
concrete. The combination of
cement and gravel is known as…
A) a solution
 B) an alloy
 C) a mechanical mixture
 D) a pure substance

Emulsified liquids, such as
homogenized milk, are referred
to as…
A) compounds
 B) colloids
 C) aqueous solutions
 D) suspensions

2.1 Evolving
Theories of Matter
How did different societies make sense of what
they observed??
What did the bee say to the flower?
“Hey bud, when do you open?
Stone Age Chemists
Lived before 8000 B.C. in middle east
 Metal not discovered, used ‘stone’ tools
 Learnt how to start, control, and use fire
for cooking, glass, ceramics, bricks

Emerging Ideas About the
Composition of Matter
350 BC *Aristotle stated that everything was
made of earth, air, fire, and water.

– Because Aristotle was well known and well
respected, his description of matter was
preferred over Democritus’s description
until 1600 AD.
From Alchemy to Chemistry

350 BC- 1600 AD- numerous alchemists (Arabic for
‘alkimiya’- “the chemist.”) practiced their pseudoscience (magic & simple experiments) trying to
change metals into gold. They were not interested
in understanding the nature of matter.

Alchemists contributed useful lab tools from their
practice. Ex. Beakers, filters, flasks, plaster of paris

In 1597, the German alchemist Andreas Libau
published ‘Alchemia’, a book describing the
achievements of alchemists and how to prepare
chemicals
New Interest in Atoms
1500s on- scientists had a greater
interest in understanding the nature of
matter and change.
 Based their theories on observations
and experimentation rather than
guesses and assumptions.
 movie

New Interest in Atoms

1600s Robert Boyle experimented
with gases and came up with proof
supporting 400 BC Democritus’
tiny particle theory.
 Boyle believed matter was
composed of tiny particles with
various shapes and sizes that
grouped together to form other
individual substances.
 He wanted to determine what each
type of particle was.
Chemistry Becomes a New
Science

1770’s- Antoine Lavoisier (French scientist)
studied chemical interactions and naming the
elements: hydrogen, oxygen, and carbon.
 Developed a system for naming chemicals
that all scientists could use the same words
 He was given the title of ‘Father of Modern
Chemistry’

The following is the most important part
of this section…focus!
1808- John Dalton (English
scientist)

- suggested matter was made up of elements that are
pure substances that contain no other substances.

He put forward the first modern theory of atomic
structure:
– Each element is composed of a particle called an
atom
– All atoms of a specific element have identical
masses
– Different elements have different atoms of different
masses
– video
Dalton
He developed the ‘Billiard Ball
Model’ where atoms are solid
spheres
1897- J.J. Thompson
(British physicist),

discovered negatively charged sub-atomic
particles electrons.

Proposed the Raisin bun model of the atom
– Atom is a positive center with negative electrons
embedded in it like raisins in a bun
– Electrons balance protons therefore atom has no
electrical charge
Thompson’s Raisin Bun Model
1904- Hantara Nagaoka
(Japanese physicist)

proposed an atomic model that resembled a
mini solar system- planetary model
– Center had a large positive charge and negative
electrons circled the positive center like planets
orbiting the sun
Nagaoka model
1907- Ernest Rutherford (British
scientist)- worked at McGill won the
Nobel Prize for work in radioactivity
– Supported Nagaoka’s model but modified it saying
electrons float around randomly
– His model suggest that atoms were empty spaces
which positive particles could pass through with a
positive central core (he called it a nucleus)
– video
*Nucleus*
Positively charged centre of an atom
 Contains protons and neutrons

Rutherford also…

Calculated that the nucleus was
only about 1/10 000th the size of
the atom
Like a green pea in a football
field.
Rutherford’s Discovery

Was a huge contribution to
atomic theory
 How he did it:
– Shot high speed positive
charged particles at thin gold
foil
– Most went through foil, but a
few deflected back because
they hit the nucleus of atom
1913- Niels Bohr, Nobel Physics
Prize,

subjected that electrons move in
a specific circular orbits (electron
shells) and they jumped between
shells by gaining or losing energy
 Created a new model of the atom
which we still use in Science 9!
Bohr Model
Late 1920’s- James Chadwick
(British Physicist)

discovered the nucleus contains
protons (+ charge) and neutrons (no
charge).
– Protons and neutrons have same masses
– Electrons has a mass of 1/1837 of either a
proton or neutron
*Protons*
Positively charged
particle in the
nucleus of an atom.
*Neutrons*
Neutral particle in
the nucleus of an
atom.
Today the 'quantum model' describes the
atom as a cloud of electrons around a
nucleus.
Subatomic Charge
Structure
Location
Size
Proton
Positive
Charge
Nucleus
Large
Electron
Negative
Charge
Orbiting
around
nucleus
Very small
Neutron
No charge
Nucleus
Large
And now the science that they
don’t teach you in textbooks…

John Dalton was a bright student- in fact
at age 12 he was put in charge of his
local school!
– How bright was he? He was reading Issac
Newton’s Principia (zzz…) in the original
Latin

Colorblindness, which he suffered from,
was for a long time called Daltonism
And now the science that they
don’t teach you in textbooks…
He wasn’t always right…screwed up on
oxygen’s vital stats ex. Atomic weight &
said water is HO7
 When he died, 40 000 people viewed
his coffin!

And now the science that they
don’t teach you in textbooks…
Lavoisier collected taxes and fees on
behalf of the gov’t. It made him so rich,
his personal earnings reached $20
million/ yr in today’s money!
 Lavoisier married a 14 year old
daughter of one of his bosses when he
was around 25!

And now the science that they
don’t teach you in textbooks…
The Father of Chemistry never
discovered an element! (Yet he made
sense of other people’s discoveries)
 In 1793 the Reign of Terror seen
Lavoisier was guillotined because he
was part of gov’t which the French
revolution overturned!


BBC Discovery the elements