Chemistry Unit: The Study of Matter

1. Chemistry Unit:The Study of Matter Grade 9 Science

2. Outline the development of scientific thought as it relates to matter and the atomic structure. • Define element and understand its relationship to the concept of matter. • Describe the understanding of the structure of the atom. • Key Words • Element atom pure substance • Hypothesis alchemist plum pudding model • Subatomic neutral electron • proton

3. Developing Models of Matter

4. Democritus (400 BCE) • Hypothezised matter was tiny particles in constant motion. • Cannot be broken apart –solid. • Eternal (unable to create or destroy) • Surrounded by an empty space. • *called particles atomos– meaning “indivisible” - ATOM

5. Aristotle(350 BCE)   • Ancient Greek philosopher. • Believed matter was made of four elements. • His theory was accepted by all.

6. Alchemy and the Middle Ages (500 – 1600 CE) • Concerned with metallurgy (study of properties of metals). • Goals- turn common metals into gold or silver. • - find a substance to give eternal life. • (the key to both is called the Philosopher’s Stone) • Developed observation, experimentation, measurement and • classification – first “scientists.” • Called “alchemists”

7. Lavoisier (1750) • 13 known substances – gold, copper, arsenic, bismuth, antimony, iron, mercury, carbon, lead, silver, sulphur, tin, zinc. • Performed experiments to show water and air were • mixtures of elements. • Defined the term ELEMENT - a fundamental pure • substance that cannot be broken down into simpler parts. • Discovered23more elements.

8. Dalton (1800) • FIRST ATOMIC THEORY • all matter is made of indivisible particles - atoms. • Atoms of each element are unique (differ by mass). • Compounds are combinations of different elemental atoms. • Atoms cannot be created or destroyed. • (Law of conservation of matter)

9. Thomson(1890) • Hypothesized (guessed) first subatomicparticles –electron. • Electrons have a small mass and negative electric charge. • Atom is sphere with equal number of positive charges mixed • with negative electrons - Plum pudding model. • Overallatom is neutral electrically.

10. Rutherford (1910) • Conducted “Gold Foil Experiment.” • Discovered the atomic nucleus. • Nucleus is a small, dense (heavy), positively charged core. • Positive charges due to another subatomic particle - protons • Hypothesized atom composed of mostly space with a centre • nucleus and small electrons floating around.

12. Chadwick (1932) • discovered the neutron in the nucleus • Neutrons have no charge and are the size of protons. • THREE subatomic particles: • - dense positive nucleus (protons and neutrons). • - negativeelectrons floated around.

13. Dalton - each element has its own kind of atom • - compounds are formed when elements link together
 - atoms cannot be created or destroyed • - billiard ball model • Thomson - discovered negatively charged electrons • - hypothesized equal positive and negative particles 
 • - plum pudding model • Rutherford - discovered nucleus (goldfoil) and positive protons • - hypothesized atoms were mostly empty space • - beehive model

15. The Atom Contains 3 subatomic particles: The dense center (nucleus) of the atom contains: Neutron - a particle with no charge. Proton - a particle with a positive charge. Electrons are tiny particles that move around the nucleus. - negative electrical charge. - same # of positive and negative charges = neutral.