1. Chapter 2 “Scientific Measurement”
Full screen view – click screen in lower right corner (Internet Explorer 4.0 & higher)
Metric System &
Converting Units using Dimensional Analysis

2. Nature of Measurements
Measurement - quantitative observation
consisting of 2 parts:
Part 1 – number
Part 2 - Unit
Examples:
20 grams
6.63 x 102 m/sec

3. Metric System In Science we use the Metric System.
Metric Prefixes are based on powers of 10.
Metric Prefixes can be used with any basic unit of measure.
Gram (g) for mass
Liter (L) for volume
Meter (m) for length
Seconds (s) for time

4. Metric Conversion Chart
Unit Equivalents
(Using meters)

5. Conversion factors You can also write it as a ratio 1 km or 1000m
A “ratio” of equivalent measurements
Start with two things that are the same:
one kilometer equals 1000 meters
Write it as an equation (unit equivalent!)
1 km = 1000 m
You can also write it as a ratio
1 km or m
1000m 1 km

6. Dimensional Analysis
A way to analyze and solve problems, by using units (or dimensions) of the measurement
Dimension = a unit (such as g, L, mL)
Analyze = to solve
Using the units to solve the problems.
If the units of your answer are right, chances are you did the math right!

7. Converting Between Units
Problems in which measurements with one unit are converted to an equivalent measurement with another unit are easily solved using dimensional analysis.
You basically multiply by one or more unit conversion factors.
You arrange them so the units cancel out and leave you with the desired unit.

8. Simple Example
We can multiply by a conversion factor to change the units .
Problem: 13 inches is how many yards?
Known: 36 inches = 1 yard.
Write as ratio 1 yard
36 inches
13 inches x yard = 0.36 yards inches

9. Dimensional Analysis
Write the given number and unit and draw a “T” chart
Set up a conversion factor (fraction used to convert one unit to another)
Place the given unit as the denominator of the conversion factor.
Place the desired unit as numerator.
Insert numbers from above table that correspond to each unit in the numerator and denominator.
Cancel the units and solve the problem by multiplying across and dividing by numbers in the denominator.

10. Example Convert 55 mm to meters 55 mm 10-3_m_ = 0.055 m 1 mm
I use “T” charts as an easier way to set up the ratios.
You multiply numbers across the top and divide by the numbers on the bottom
The above problem is just like this
55mm x m
1mm

11. Example 2 step conversion
Convert 7000 mL to hectoliters
7000 mL L 1 hL__ = hL
1 mL 100 L