2.  A common number used in chemistry is 602,000,000,000,000,000,000,000  What is that number in scientific notation? 6.02 x 10 23

3.  4300  505,000  0.0047  2.7 x 10 3  8.8 x 10 -4  1.7 x 10 -1 4.3 x 10 3 5.05 x 10 5 4.7 x 10 -3 2700 0.00088 0.17

5.  Every measurement requires two parts. 1) Number 2) Unit Example: 20.0 g 1.22 g/ml  Measure to the correct number of decimal places (significant figures)

6.  Measure to the number of decimal places that you can read on your ruler, balance, or graduated cylinder.  Always measure to one more decimal place. This is the estimated or uncertain digit.

7. 2.34 cm

8. 25.7 cm

9. 52.9 ml

10. 43.0 ml

11. 373.35 g

12. 27.70 g

13.  All nonzero numbers are significant. Ex: 276 (3 sig figs) 32, 184 (5 sig figs)

14.  Zeros between numbers are significant. Ex: 4009 (4 sig figs) 200.05 (5 sig figs)

15.  Zeros at the beginning of a number (leading zeros) are NOT significant. Ex: 0.003 (1 sig fig) 0.0000057 (2 sig figs)

16.  Zeros at the end of a number without a decimal in the number are NOT significant. Ex: 25, 000 (2 sig figs) 900 (1 sig fig)

17.  Zeros at the end of a number with a decimal in the number are significant. Ex: 20.0 (3 sig figs) 0.07300 (4 sig figs)

18.  Do not include the exponent in numbers written in scientific notation. Ex: 6.223 x 10 8 (4 sig figs)

19.  How many significant figures are in the following measurements? 1) 42.56 g 4 2) 0.00793 3 3) 8000 1 4) 2.70 x 10 9 3

20. Multiplication and Division Your answer should contain the same number of significant figures as the least number of significant figures in the problem. Ex: 45.89 cm x 3.26 cm =? Calculator = 149.6014 Answer = 150. cm 2

21.  Ex: 45.98 cm 2 / 5.7 cm = Calculator = 8.06666666…. Answer = 8.1 cm

22. Ex: How many significant figures should you have in your answer to the following problem? 3.75 x 21.489 / 2.73 = 3

23.  Your answer should contain the same number of decimal places as the least number of decimal places in the problem.  Ex: 18.723 g + 2.11 g =  Calculator= 20.833  Answer = 20.83 g

24.  285.722 g – 58.1 g =  Calculator = 227.622 g  Answer = 227.6 g

25.  42.675 – 3.91 =  9.8  Subtraction = 38.765  Round off to correct number of decimal places  38.77/9.8  Calculator = 3.956122…  Answer = 4.0

26. Metric System PREFIXSYMBOLMEANING gigaGbillion (1 x 10 9 ) megaMmillion (1 x 10 6 ) kilokthousand (1 x 10 3 ) hectohhundred (1 x 10 2 ) dekadaten (1 x 10 1 ) _____________________________________________ decidtenth (1 x 10 -1 ) centichundredth (1 x 10 -2 ) millimthousandth(1 x 10 -3 ) micro  millionth (1 x 10 -6 ) nanonbillionth (1 x 10 -9 )

27. 1. How many cm are in a meter? 100 2. Which is larger, a milligram or a microgram? milligram 3. What does the prefix nano mean? one billionth 4. What is the symbol for 100? h 5. How many grams are in a megagram? one million