Significant Figures - Download as PowerPoint by cuiliqing


									Title: Significant Figures and
Objective: I will be able to determine the amount
of significant figures when given a quantifiable
number and round appropriately.
Questions: What is significant figures and how do
I round?
     Significant Figures
 Some digits in an number may be
exact while others may be uncertain,
 so chemists have devised a way to
determine which digits are the most
 Rule #1 – All numbers that are
 not zero are always significant
-487 miles has 3 significant figures
-3.1478654 has 8 significant figures
Rule #2-Zeros appearing between
  nonzero digits are significant

40.7 lbs has 3 significant figures
87,009 lbs has 5 significant figures
Rule #3 – Zeros in front of non-
zeros digits are NOT significant
• Examples:
0.009587 m has 4 significant figures
0.0000009 m has 1 significant figure
  Rule #4-Zeros at the end of a
  number and to the right of a
  decimal point are significant
• Examples:
  – 85.00 g has 4 significant figures
  – 9.0700 g has 5 significant figures
Rule #5 – Zeros at the end of a
number with no decimal may or
may not be significant, if there is
a decimal point at the end of all of
the zeros then the zeros are
significant .
 -2000 m has 1 significant figure or has 4
   significant figure depending on if the zeros
   are place holders
 -2000. m has 4 significant figures because of
   the decimal point.
Rounding Rules
• Use only the 1st number to the right of the
  last sig. fig. number to decide whether or
  not to round.
  •   Less than 5, do NOT round
  •   More than 5, round the last sig. fig. up by 1
• When using a calculator wait until the
  very end before rounding. Try to keep as
  many digits in the calculator until you
  come to the very end.
     Multiplying and Dividing
• Keep as many sig figs in your answer as
  are in the piece of data with the least
  number of sig figs.

2.37 cm x 15.67 cm x 7.4 cm = 274.82046
(keep two sig figs) = 2.7 x 102 cm3
     Addition and Subtraction
1. Keep the same number of decimal places
  in your answer as the least precise
  measurement in your calculation.

34.039 m + 0.24 m + 1.332 m + 12.7 m =
  48.311 m
(keep one decimal place) = 48.3 m
          Scientific Notation
• This is a number that has 1 digit left of the
  decimal point.
  – Example 3.4 x 103
Exponent: Positive or Negative?
• When convert expanded numbers into scientific
   – If you move the decimal to the left the exponent
     number is postive
   – If you move the decimal to the right the exponent is
• When converting from scientific notation back to
  expanded form:
   – If you move the decimal to the right the exponent
     number is negative
   – If you move the decimal to the left the exponent is
             Your Calculator
• Remember Order of Operations:
  –   Parentheses
  –   Exponents
  –   Multiplication and Division
  –   Addition and Subtraction
• Use the button “EE” on calculator
- Bring Calculator!

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