Measurements SI and Metric units

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MeasurementsSI and Metric units
Volume liter (L) or cubic meter (m3)
Temperature C or K
Time second (s)
Length meter (m)
Mass gram (g) or kilogram (kg)
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Scientific Notation

• To express LARGE and small numbers
• Speed of light 300,000,000 m/s
• 1 megaelectron volt
• 0.000000000000162 J
• Standard scientific notation
• a.b x 10n
• a and b are coefficients,
• n is exponent

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• Speed of light 300,000,000 m/s
• 3.0 x 108 m/s
• 1 megaelectron volt
• 0.000000000000162 J
• 1.62 x 10-13 J
• Number of atoms in 12 grams of carbon?
• 6.023 x 1023!!!

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Problems

• Write 350 g in scientific notation
• 3.50 x 102 g
• Write 2.4 x 10-3 L in standard notation
• 0.0024 L
• Which is larger 4.9 x 10-3 cm
• or 5.5 x 10-9 cm?
• 4.9 x 10-3 cm

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Prefixes

• nano (n) 1 billionth 0.000000001 1x10-9
• micro (µ) 1 millionth 0.000001 1x10-6
• milli (m) 1 thousandth 0.001 1x10-3
• centi (c) 1 hundredth 0.01 1x10-2
• deci (d) 1 tenth 0.1 1x10-1
• kilo (k) 1 thousand 1,000 1x103
• mega (M) 1 million 1,000,000 1 x 106
• giga (G) 1 billion 1,000,000,000 1x109

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Measured vs. Exact Numbers

• Measured Length, volume, weight, blood
  pressure, etc.
• Exact COUNTED
• Eggs, students, bagels, votes (?)
• Identities
• 12 inches 1 foot
• 1 kg 1000 grams

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Significant Figures

• Accuracy vs. Precision

Accuracy Close to actual value BULLSEYE Precisi
on Reproducible Bad shot, but many in the same
spot
When measuring values, the LAST digit is always
UNCERTAIN.
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Rules for Significant Figures

• All non-zero numbes are SIGNIFICANT
• ex. 1.23 g
• Zero between non-zero numbers are SIGNIFICANT
• ex. 2.05 m
• Zero at RIGHT end of value is SIGNIFICANT
• ex. 4.00 kg
• All digits in coefficient in SCI NOTE are
  SIGNIFICANT
• ex. 3.20 x 10-2 cm
• Zero at LEFT end of value is NOT significant
• ex. 0.22 ft
• Zero as placeholder is NOT significant
• ex. 8,003,239

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Problems

• How many significant figures in the following
• 20.60 ml
• 60,800,000 g
• 5.00 x 10-3 lbs
• 0.000250 cm

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3
3
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The fail-proof trick? Convert to Scientific
Notation and COUNT digits in COEFFICIENT