2. Various physical & chemical techniques have been used to enhance and preserve our food. The most common way food goes bad (spoils) is when bad bacteria occur in too large a number. Food Chemistry

3. Methods for Preserving Food –Heating and Freezing Heating (cooking)- temporarily sterilizes food (kills the bacteria) Freezing (storage) – halts the growth of bacteria –Salting (beef jerky) Salt removes water, by osmosis, from the food and the bacteria in it. This changes the taste of the food but kills the bacteria.

4. –Fermentation – This process uses beneficial bacteria (lactobacilli) to create a natural preservative (lactic acid). Sauerkraut was made because it lasted long and had vitamin C to fight off Scurvy. Alcoholic beverages are also made this way. Methods for Preserving Food

5. -Smoking – smoking your bacon or fish introduces antioxidants that help control the number of bacteria.

6. The science of producing and using metals Copper age- made tools out of copper -Annealing (heating before being hammered) made Cu easy to manipulate and strengthened it. Stronger tools and Weapons. -Smelting – separating a metal from other compounds using heating. Most Copper is mixed with other compounds and was until this time unusable.

7. Bronze age – Bronze is made from copper & tin. It is called an alloy (mixture of metals). Iron Age – started smelting Iron in 1200 B.C. ◦ Later figured out how to add carbon to make steel. Note: Copper to Bronze to Iron was a progression to making stronger metals that enabled better tools (farming) and weapons. People could change matter, but did not understand it.

8. Aristotle ◦ All matter was comprised of fire, earth, water, & air. Early Descriptions of Matter

9. Aristotle ◦ There was no smallest part of matter. In other words you could cut an element in half forever & still have a piece of that element. ◦ Democritus challenged Aristotle on this last point saying that there were particles called atoms that were indivisible. (Aristotle was in the in crowd so no one listened to Democritus and set back science for 2000 years give or take.) http://communicationtheory.org/aristotle%E2%80%99s- communication-model/ Early Descriptions of Matter

10. Alchemy – branch of early science that wanted to change one substance into another. (ideally lead into gold. WE can do this now actually just not cost effective) ◦ Although not successful they improved lab equipment and produced many useful compounds. Alchemy

11. Robert Boyle – tiny particles make up gases Antoine Lavoisier -experimentally came up with the Law of Conservation of Mass. (Mass of reactants = Mass of Products) Early Scientists

12. John Dalton (1766 - 1844) His “Billiard Ball” model lasted for over 100 years, until later technology showed that atoms or not indivisible!  Atoms are tiny, indivisible particles of elements.  All elements are composed of atoms.  Atoms of the same element are identical.  Chemical reactions occur by a rearrangement of atoms.  Atoms combine in fixed ratios to form compounds. Matter is made from Atoms, which look like small spheres

13. (1856 – 1940) Hooked up materials in a cathode ray tube & found electrons are ejected. Plum pudding model of the atom electrons evenly scattered throughout the atom In Thomson’s Model, the atom was made up of a positively charged sphere (protons) with negative particles embedded in it (electrons). Net charge = 0. Thomson’s Model was labelled the “Raisin Bun”

14. (1871 – 1937) He expected… high-speed particles gold foil Found majority of an atoms mass is in the center. The center is made up of positive particles (known as the nucleus). Electrons fly around the outside (in orbit). He used a bee hive model.

15. What ACTUALLY happened… gold foil high-speed particles Rutherford was surprised when all the particles did not go straight through the gold foil. Some bounced back and others were sharply deflected. He then realized that each atom must have a dense core of positive charge. He called the dense centre the nucleus. Rutherford redefined the Model of the atom, by making a tiny positively charged nucleus, surrounded by electrons. Rutherford calculated the size of the nucleus to be about 1/10 000 of the size of the atom.

16. (1885 – 1962) *Found that different electrons have different amounts of energy using spectral analysis. *Bohr model of the atom shows orbits representing different energy levels. ◦ Energy exists in small units called quanta ◦ Electrons circle the nucleus in orbit at a fixed distance having a fixed amount of energy Li Lithium atom F Fluorine atom

17. ◦ Bohr concluded that:  Electrons surround the nucleus at specific energy levels (2,8,8,18)  Since electrons can’t fall below that lowest energy level, negatively charged electrons don’t merge with the positively charged nucleus.

18. When atoms are heated, bright lines appear called line spectra. An electron absorbs energy to “jump” to a higher energy level. –When an electron falls to a lower energy level, energy is emitted. Line Spectra

19. Electrons are clouds of negative charge occupying the whole space at once at different energy levels.

20. Electrons are thought of as a “cloud” of negative charge, instead of a tiny negative particle. TODAY’S MODEL The idea of electron movement is abandoned. Instead, electrons “occupy” the whole space all at once at different energy levels (cloud). The electron cloud surrounds a nucleus containing 2 types of particles called nucleons: PROTONS and NEUTRONS Protons have a positive electrical charge, and Neutrons have no electrical charge.

21. Do p.27 of the Notepack using your notes and textbook. Do #1-8 & 11 (pg.25) (Textbook). Do # 2, 3, 5-13, 15-17 (pg. 27) (Textbook). Quiz on Section 1 – coming soon…