1. SEPTEMBER 6, 2012 CHEMISTRY 20

2. A JOKE…

3. AGENDA Taylor Wilson Significant Figures SI Units Worksheet

4. This is Taylor Wilson. What do you think he is well known for? TAYLOR WILSON

5. Link to Video

6. TAYLOR WILSON “The Boy Who Played With Fusion”

7. ACCURACY & PRECISION Accuracy tells us how close we were to a desired result. Precision tells us how close our results were to each other. How reproducable our results are. It is possible to have a measurement system that is accurate, but not precise. Precise but not accurate. Both or neither.

8. SCIENTIFIC NOTATION A way of writing numbers that are too big or too small to be conveniently written in standard form Commonly used in calculators and often used by scientists, engineers, and mathematicians.

9. SCIENTIFIC NOTATION How to write in scientific notation: Take your number Ex: 34500 Convert it to a decimal. Ex: 3.45 Write x10 b after it, where b is the number of spaces the decimal has moved. Ex: 3.45 x 10 4 = 34500

10. SCIENTIFIC NOTATION

11. Convert the following to scientific notation: 545000 23400000 0.0012.00004901

12. SIGNIFICANT FIGURES Why are significant figures important? Because they tell us how accurate our results are.

13. SIGNIFICANT FIGURES How do we determine the number of significant figures? Four simple Rules!

14. SIGNIFICANT FIGURES Rule 1: All non-zero digits, are ALWAYS significant. EX: 345  3 significant figures (sig figs)

15. SIGNIFICANT FIGURES Rule 2: All zeroes between non-zero digits, are ALWAYS significant. EX: 3091  4 sig figs

16. SIGNIFICANT FIGURES Rule 3: Zeroes placed before other significant digits are NOT significant. EX: 0.32  2 sig figs EX: 04449  4 sig figs

17. SIGNIFICANT FIGURES Rule 4: Zeroes placed after other significant figures are only significant if they are behind(after) a decimal. EX: 117000  3 sig figs EX: 65.0  3 sig figs

18. MULTIPLYING/DIVIDING SIGNIFICANT FIGURES When multiplying/dividing, the number of sig figs in the answer should be the same as the number that has the fewest number of sig figs being multiplied/divided. EX: 2480 x 12.00 = 29,760 = 2.98 x 10 4 3 4 3 Note that the answer gets rounded to the nearest place. It is usually easier to write your answers in scientific notation.

19. ADDING/SUBTRACTING SIGNIFICANT FIGURES When adding/subtracting, your answer should have the same number of decimal places as the number with the least amount of decimal places being added or subtracted. EX: 45.002 + 13.6 = 58.6 Once again the answer is rounded to show the correct number of significant digits.

20. ASSIGNMENT Work on the booklet that is being handed out. It is due Wednesday (Sept. 12)