1. CH. 1 - MEASUREMENT
I. Units of Measurement

2. m V D = A. Derived Units 1 cm3 = 1 mL 1 dm3 = 1 L
Combination of base units.
Volume (mL or cm3)
length  width  height
1 cm3 = 1 mL
1 dm3 = 1 L
D = m V
Density (g/mL or g/cm3)
mass per volume

3. B. Density
Liquids
Material
Density (gm cm-3)
Water at 4 C
1.0000
Water at 20 C
0.998
Gasoline
0.70
Mercury
13.6
Milk
1.03
Solids
Magnesium
1.7
Aluminum
2.7
Copper
Gold
19.3
Iron
7.8
Lead
11.3
Platinum
21.4
Uranium
18.7
Osmium
22.5
Ice at 0 C
0.92
Density of a substance determines whether that substance will float or sink in a liquid
Density of a substance does not change

4. B. Density
Mass (g)
Volume (cm3)

5. B. Density
Direct Proportion y x
Inverse Proportion y x

6. C. Measurement Measurement is uncertain because
1. Instruments may have errors
2. Involves estimation
Measurement =
all certain digits + 1 uncertain digit
(estimate)

7. Accuracy vs. Precision ACCURATE = CORRECT PRECISE = CONSISTENT
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

8. D. Percent Error
Indicates accuracy of a measurement – you will be using this calculation in the lab
your value
(observed value)
accepted value

9. D. Percent Error % error = 2.94 %
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 = 2.94 %
Always report %’s to the hundredths place!

10. E. Significant Figures Indicate precision of a measurement.
Recording Sig Figs
Sig figs in a measurement include the known digits plus a final estimated digit that falls between the tick marks on a measuring device
2.32 cm

11. E. Significant Figures Counting Sig Figs Count all numbers EXCEPT:
Leading zeros
what about:
Trailing zeros without a decimal point -- 2,500
what about:

12. Counting Sig Fig Examples
E. Significant Figures
Counting Sig Fig Examples
4 sig figs
3 sig figs
3. 5,280
3. 5,280
3 sig figs
2 sig figs

13. E. 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

14. E. Significant Figures + 4.25 24.3185 ?? 3.75 mL + 4.1 mL 7.85 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.
3.75 mL mL
7.85 mL
3.75 mL mL
7.85 mL
+ 4.25 ??
 7.9 mL

15. F. 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.

16. F. Scientific Notation Practice Problems 1. 2,400,000 g 2. 0.00256 kg
3. 7  10-5 km
 104 mm
2.4  106 g
2.56  10-3 kg km
62,000 mm

17. F. Scientific Notation Calculating with Sci. Notation
(5.44 × 107 g) ÷ (8.1 × 104 mol) =
Type on your calculator:
ENTER =
5.44 7
8.1 EE ÷ 4 EE =
= 670 g/mol
= 6.7 × 102 g/mol
H.O.