1. CH. 1- MEASUREMENT
II. Using Measurements

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

3. B. Percent Error Indicates accuracy of a measurement your value
accepted value

4. B. Percent Error % error = 2.9 %
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 = 2.9 %

5. 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
C. Johannesson

6. C. Significant Figures Counting Sig Figs Count all numbers EXCEPT:
Leading zeros
Trailing zeros without a decimal point -- 2,500

7. Counting Sig Fig Examples
C. Significant Figures
Counting Sig Fig Examples
4 sig figs
3 sig figs
3. 5,280
3. 5,280
3 sig figs
2 sig figs

8. C. Significant Figures (13.91g/cm3)(23.3cm3) = 324.103g 324 g
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
4 SF
3 SF
3 SF
324 g

9. C. Significant Figures  350 g 3.75 mL + 4.1 mL 7.85 mL 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.
 350 g
3.75 mL mL
7.85 mL
3.75 mL mL
7.85 mL g
+ 130 g
354 g
224 g
+ 130 g
354 g
 7.9 mL

10. C. Significant Figures Practice Problems 5. (15.30 g) ÷ (6.4 mL)
4 SF
2 SF
= g/mL
 2.4 g/mL
2 SF g g
 18.1 g
18.06 g

11. 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.
C. Johannesson

12. D. Scientific Notation Practice Problems 2.4  106 g 7. 2,400,000 gkg
9. 7  10-5 km
 104 mm
2.4  106 g
2.56  10-3 kg km
62,000 mm

13. E. Scientific Method Hypothesis - testable prediction
Theory - explanation of “why”
based on many observations & experimental results
Scientific Law - prediction of “what”
describes a pattern in nature