1. I. Using Measurements (p. 44 - 57)
CH. 2 - MEASUREMENT
I. Using Measurements
(p )
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2. A. Accuracy vs. Precision
Accuracy - how close a measurement is to the accepted value
Precision - how close a series of measurements are to each other
ACCURATE = CORRECT
PRECISE = CONSISTENT
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3. C. Johannesson

4. B. Percent Error your value accepted value
Indicates accuracy of a measurement
your value
accepted value
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5. B. Percent Error % error = ____ %
A student determines the density of a substance to be 1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL.
% error = ____ %
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6. C. Significant Figures Indicate precision of a measurement.
Recording Sig Figs
Sig figs in a measurement include the known digits plus a final estimated digit
2.35 cm
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7. C. Significant Figures Counting Sig Figs (Table 2-5, p.47)
Count all numbers EXCEPT:
Leading zeros
Trailing zeros without a decimal point -- 2,500
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8. Counting Sig Fig Examples
C. Significant Figures
Counting Sig Fig Examples
sig figs
sig figs
3. 5,280
3. 5,280
sig figs
sig figs
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9. C. Significant Figures (13.91g/cm3)(23.3cm3) = 324.103g
Calculating with Sig Figs
Multiply/Divide - The # with the fewest sig figs determines the # of sig figs in the answer.
(13.91g/cm3)(23.3cm3) = g
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10. C. Significant Figures 224 g + 130 g 354 g 224 g + 130 g 354 g 3.75 mL
Calculating with Sig Figs (con’t)
Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer.
224 g
+ 130 g
354 g
224 g
+ 130 g
354 g
3.75 mL mL
7.85 mL
3.75 mL mL
7.85 mL
 ___ mL
 ___ g
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11. C. Significant Figures Calculating with Sig Figs (con’t)
Exact Numbers do not limit the # of sig figs in the answer.
Counting numbers: 12 students
Exact conversions: 1 m = 100 cm
“1” in any conversion: 1 in = 2.54 cm
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12. C. Significant Figures Practice Problems = 2.390625 g/mL 6. 18.9 g
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13. D. Scientific Notation 65,000 kg  6.5 × 104 kg
Converting into Sci. Notation:
Move decimal until there’s 1 digit to its left. Places moved = exponent.
Large # (>1)  positive exponent Small # (<1)  negative exponent
Only include sig figs.
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14. D. Scientific Notation Practice Problems 7. 2,400,000 g 8. 0.00256 kg
 10-5 km
 104 mm
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15. D. Scientific Notation (5.44 × 107 g) ÷ (8.1 × 104 mol) =
Calculating with Sci. Notation
(5.44 × 107 g) ÷ (8.1 × 104 mol) =
Type on your calculator:
EXP EE
EXP EE
ENTER
EXE
5.44 7
8.1 ÷ 4
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16. E. Proportions Inverse Proportion Direct Proportion y x y x
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