#  What is the definition of significant?  How is “Digit” used in this phrase?

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 What is the definition of significant?  How is “Digit” used in this phrase?

 Nonzero digits 654  Zeros between nonzero digits 6042  Zeros to the right of a nonzero digit and to the left of a decimal 4230.  Zeros to the right of a nonzero digit and to the right of a decimal 0.30

 Zeros to the left of decimal in values less than one 0.82  Zeros to the right of decimal and to the left of the first nonzero digit 0.082

 Exact Conversion factors are considered to have unlimited significant digits 1000 mm = 1 m  Counting numbers have unlimited sig digs 6 doughnuts

 How many significant digits? ◦ 1044(4) ◦ 10(1) ◦ 10. (2) ◦ 0.10(2) ◦ 130(2) ◦ 1040(3) ◦ 0.12(2) ◦ 1060220(6) ◦ 0.3000(4) ◦ 1040. (4)

Why do we use an elevator? Why is a fax machine an office requirement? Why do we drive a car to work? Which is faster, a whisk or a blender? Why do we use a microwave oven?

Why should you use scientific notation? When should you use scientific notation?

 602200000000000000000000  This number represents the number of molecules in one “MOLE” of material. BUT ◦ You have to know the formula of the material.  602000000000000000000000 ◦ Write it five times!

 602000000000000000000000  Want to write it five more times?  Lets write it again like this: ◦ 6.022 X 10 23 ◦ This is called scientific notation. ◦ Write this one five times!  Which would you rather write?  WHY?

 What do you notice about this number? ◦ One number to the left of the decimal ◦ This is called scientific notation. ◦ 60.22 x 10 22 is NOT scientific notation  How do you punch Avogadro's number into a calculator? WARNING, it varies.

 6.022 x 10 23 + 4.522 x 10 22 ◦ These numbers cannot be added as written. ◦ The exponents must be the same in order to add or subtract.  = 6.022 x 10 23 + 0.4522 x 10 23  = 6.474 x 10 23

 6.022 x 10 23 x 2.37 x 10 22

 I’m making omelets for a bunch of people. I need a lot of eggs.  What is “a dozen” eggs?  Express a dozen eggs in scientific notation: ◦ 1.2 X 10 1  Can you think of two mathematical ways to express TWO dozen eggs (use scientific notation)? ◦ 2 x (1.2 X 10 1 ) ◦ (1.2 X 10 1 ) + (1.2 X 10 1 )

 Properly expressed, a SciNot value will have one nonzero digit to the left of the decimal.  In converting to SciNot: ◦ 165467 ◦ For each place you move the decimal left, increase the exponent by 1 ◦ = 1.65467 X 10 5 (6 Significant Digits)  In converting to SciNot: ◦ 0.00002350 ◦ For each place you move the decimal right, decrease the exponent by 1 ◦ = 2.350 X 10 -5 (4 Significant Digits)

 The language of chemistry is mathematical and verbal.  The typical measurement system of chemistry is the SI system. ◦ Length = Meters (m) ◦ Mass = Grams (g) ◦ Volume = Liters (L) ◦ Temperature = Kelvins (k) or degrees celsius °C ◦ Pressure = Pascals (Pa) or Atmospheres (atm)  There are more conversions that we will cover later.

 Metric conversions – Remember this acronym: ◦ KHDmdcm g L King Hector Died monday drinking chocolate milk Use this acronym when converting from one metric unit to another metric unit.

 Example: ◦ Convert 650 mL (milliliters) to L Liters K H D (L) d c m Since you have to Jump 3 places to the left, move the decimal point 3 digits to the left. You have to move 3 places left. 6 5 0. = 0.650 L

 Example II: ◦ Convert 7.25 Km (Kilometers) to m (meters) K H D (m) d c m K H D (L) d c m Since you have to Jump 3 places to the right, move the decimal point 3 digits to the right and add a zero. You have to move 3 places right. 7. 2 5 0. = 7250. m

 Try! Convert 72.5 g to mg  Answer: 72,500 mg  Try one more: Convert 26 HL to dL  Answer: 26,000 dL

1. Convert 65 mg to g 2. How many Decagrams are in 5 grams? 3. How many kilograms are in 7588 grams? 4. How many deciliters are in 2.7 liters? 5. How many km are in 102,000 cm?

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