Scientific Measurement Ch. 3
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Scientific Measurement
Ch. 3Why are precise measurements
and calculations essential to the
study of chemistry?
(3.1) Measurements• Quantity that has a number
and unit
Accuracy and Precision• How close a measurement comes
to the actual value of what is being measured
• How close a series of measurements are to one another
Significant Figures
KNOW the rules for determining sig figs
Pgs. 66-67
Measured values having digits that are known with certainty and a final digit that is estimated
1) ALL non-zero numbers are ALWAYS significant.
2) ALL zeroes between non-zero numbers are ALWAYS significant.
3) ALL zeroes which are to the right of the decimal point AND at the end of the number are ALWAYS significant.
4) ALL zeroes to the left of a decimal point and in front of nonzero digits are not significant.
48,923 3.967 500.06 0.0004 8.1000 501.040 3,000,000 10.0
Sig Figs in Calculations
Many-Places Rule
Mult./Div. – how many sig figs in least
Plus/Minus – no. of places in least
305.1 x 35
5400 ÷ 9.89
305.7 + 35.035
5403 - 139.89
Percent ErrorError = Experimental value - Theoretical
Percent error =
Scientific Notation • 6.02 x 1023
(see pg. R56 of text for more
practice)
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