2.  Heating and Freezing food temporarily sterilizes the food, meaning the micro- organisms are killed.  Salting is used to preserve meat and fish, by drawing the moisture out of the meat, killing the micro-organisms or leaving them inactive.  Fermentation is a biochemical food preserving technique involving the bacteria lactobacilli. They are present on all living things, and convert sugars and starches to lactic acid. Lactic acid is a preservative that prevents growth of bacteria.

3.  Metallurgy is the science of producing and using metals.  Copper was one of the earliest metals produced, and a process called "annealing" enhanced the qualities of the copper.  Annealing is the process of heating copper, the result is that a much stronger tool can be created.  "Smelting" is the process of heating copper ore to high temperatures to drive out any impurities in the metal and be left with pure copper

4.  The philosopher Aristotle believed that there were only 4 types of matter: Earth, Air, Fire, and Water.  This belief continued for 2000 years.

5.  This was a combination of chemistry and magic.  Usually alchemy is described as parlour tricks, and most people studied alchemy with the hopes of turning lead into gold.  Alchemists where the first group to begin to question Aristotle's notion of the four states of matter.  At this time the idea of the "atom" began to be debated among alchemists.

6. John Dalton “billiard ball” model or “solid sphere” model

7.  Model: billiard ball model or solid sphere model ◦ The atom is the smallest particle of matter ◦ For a given substance, atoms are identical in size, shape and mass ◦ Smallest part of an element that can take part in chemical change and combined in whole numbers ◦ Atom is indivisible, unchangeable and indestructible

8. J.J. Thompson “plum pudding” model

9.  Model: plum pudding model ◦ The atom is a solid bulk of positive charge in which negative charges are dispersed throughout.

10. Ernest Rutherford Nuclear Model

11.  Model: “nuclear” model ◦ the positive charges and mass of the atom is concentrated in the center of the atom or the nucleus ◦ The negatively charged particles are moving rapidly around the nucleus

12. Neils Bohr Bohr model “satellite” or “solar system” model

13.  Electrons are arranged in definite energy levels (shells)  Electrons follow a prescribed orbit around the nucleus  Electrons may be dislodged from orbits (energy levels) when they absorb or release energy.

14. Wave mechanical model or Electron cloud model Erwin Schrodinger Louis de Broglie

15.  Model: Electron Cloud Model ◦ Electron has wave-like properties ◦ Electrons exist in definite energy levels ◦ Location of the electron is uncertain, described as being found in a certain region of space around the nucleus ◦ Theses regions of space are called the cloud Homework: 1.Read Science 10 p. 18 -25 2.complete Check and Reflect # 1-8, due next day.