Ch. 2 - Measurement

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Ch. 2 - Measurement

• I. Units of Measurement (p.34-45)
• Number vs. Quantity
• SI Base Units Prefixes
• Derived Units
• Density Calculations

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A. Number vs. Quantity

• Quantity - number unit

UNITS MATTER!!
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B. SI Units
Quantity Symbol
Base Unit
Unit Symbol
Length- I
meter
m
Mass- m
gram
g
Time- t
second
s
Temp- T
kelvin
K
Current- I
ampere
A
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B. SI Units
Prefix
Pre- Symbol
Factor
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C. Derived Units

• Combination of base units.
• Volume - length ? length ? length
• 1 cm3 1 mL 1 dm3 1 L
• Density - mass per unit volume (g/cm3)

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Problem Solving Steps

• 1 Givens
• 2 Unknowns
• 3 Equations
• 4 Answer

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D. Density

• An object has a volume of 825 cm3 and a density
  of 13.6 g/cm3. Find its mass.

GIVEN V 825 cm3 D 13.6 g/cm3 m ?
WORK m DV m (13.6 g/cm3)(825cm3) m 11,220
g
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Problem Solving Steps

• 1 Givens
• Include quantity, number, unit symbols
• 2 Unknowns
• Include quantity unit symbols
• 3 Equations
• Base equation manipulated equation
• 4 Answer
• Do the units agree? Is it reasonable?

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D. Density

• 1) A liquid has a density of 0.87 g/mL. What
  volume is occupied by 25 g of the liquid?

GIVEN D 0.87 g/mL V ? m 25 g
V 28.7 mL
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D. Density

• 2) You have a sample with a mass of 620 g a
  volume of 753 cm3. Find density.

GIVEN m 620 g V 753 cm3 D ?
D 0.82 g/cm3