1. CH. 2 - MEASUREMENT
I. Using Measurements

2. Activity – Significant figures & measurement
With a partner, read all the instructions for the activity!
Go to one of the lab stations in the back of the room and, using materials provided, complete the procedure and answer the questions that follow…on your own paper!!
Return to your seats to read the passage on the back and complete the questions.

3. 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

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

6. % error = ____ % B. Percent 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 = ____ %

7. 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

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

9. 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

10. (13.91g/cm3)(23.3cm3) = 324.103g C. Significant Figures
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

11. C. Significant Figures
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

12. 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

13. C. Significant Figures
Practice Problems
5. (15.30 g ) ÷ (6.4 mL)
= g/mL g g
 _____g
18.06 g

14. 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

15. Practice Problems 7. 2,400,000 g 8. 0.00256 kg 9. 7  10-5 km
D. Scientific Notation
Practice Problems
7. 2,400,000 g kg
 10-5 km
 104 mm

16. 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