1. Measurement

2. Measurement: Length (m)cm 1 2 3 4
3.1
3.2
3.3
Increment = 0.1 cm
Measurement:
3.2 6 cm
“certain” digits
“uncertain” digit
estimation required
Uncertainty: +/
3.25 cm
cm...
3.27 cm

3. Measurement: Temperature (ºC)
25. 2 ºC
30 ºC
“certain” digits
“uncertain” digit
25 ºC
Uncertainty: +/- 0.1ºC
24 ºC
23 ºC
Increment = 1 ºC
25.1 ºC
ºC...
25.3 ºC
22 ºC
21 ºC
20 ºC

4. Measurement: Volume (L)
50 mL Graduated Cylinder
Measurement:
23. 5 mL
“Meniscus”
25 mL
“certain” digits
“uncertain” digit
24 mL
23 mL
22 mL
21 mL
Increment = 1 mL
20 mL
Uncertainty: +/- 0.1 mL
23.4 mL
mL...
23.6 mL

5. Measurement: Mass (g) 28.8301 g 35.48 g Top Loading Balance
Analytical Balance
Measurement:
Measurement: g
35.48 g
Uncertainty: +/ g
Uncertainty: +/ g
35.47 g
g...
35.49 g g
g... g

6. Significant Figures (Sig. Figs.)
What are the digits in a measurement that really matter?
35.48 g g
Yes, even the uncertain digit counts as a sig. fig.!
4 Sig. Figs.
6 Sig. Figs.

7. Significant Figures: Other Examples
Measurement
When a decimal point is displayed, all trailing zeros count as sig. figs.
grams
6 Sig. Figs.
grams
Captured zeros always count as significant figures
7 Sig. Figs.
grams
Leading zeros do NOT count as significant figures
3 Sig. Figs.

8. Significant Figures: Other Examples
Measurement
When a decimal point is displayed, all trailing zeros count as sig. figs.
grams
Leading zeros do NOT count as significant figures
4 Sig. Figs.
1,200 grams
No Decimal Point Displayed!
2 Sig. Figs.
1,200. grams
Decimal Point IS Displayed!
4 Sig. Figs.

9. Significant Figures: Scientific Notation
Measurement
How would we write this with 3 significant figures?
1200 grams
1200 grams
1200. grams
2 Sig. Figs.
4 Sig. Figs.
Scientific Notation
1.20  103 grams
3 Sig. Figs.