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 pseudo-science (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

DaltonHe 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

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

Late 1920’s- James Chadwick (British Physicist)

*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 Structure

Charge 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