Conversions
Conversion factors are ways of relating quantities or values of two differing units.
Some examples of values that could
be used as conversion factors would be:
2.54 centimeters = 1.00 inch
0.621 miles = 1.00 kilometer
1.00 quart = 0.946 liters
454 grams = 1.00 pound
You can find more of these in your textbook.
What is important is to learn how to use them to get from the value and
unit you have been given to the value and unit that is desired.
All of the above equalities can be rewritten as ratios.
For example:
2.54 centimeters = 1.00 inch
If we divide both sides of the equation by 1.00 inch
2.54 centimeters
1.00 inch
=
1.00 inch
1.00 inch
the result is
2.54 centimeters
1.00 inch
=
1
We now have a conversion factor relating centimeters and inches. Note that we could just have easily divided
both sides of the equation by 2.54 centimeters and the result would have been “flipped” but still equal to 1.
The conversion factor is useful to change from one unit to another because anything you multiply by
“1” is still
the same value, even if it looks different.
For the rest of this paper we will be using notations called “trees”.
They are a way to keep units aligned to see more
easily what goes where.
The following is an example of the multiplication using fractions followed by the same
multiplication in “tree” form.
5.00 inches = ? centimeters
12.7 centimeters
=
(5.00 inches)
2.54 centimeters
1.00 inch
As the units become more complex, this form can become confusing and cumbersome.
Below is the “tree” form
of this calculation.
It keeps the numerators (tops) and denominators (bottoms) more in line with each other to
lessen confusion about what is multiplied and what is divided.
12.7 centimeters
=
2.54 centimeters
1.00 inch
5.00 inches
The trick is to put what you were given, or what you
have
, in the top left “box” and then line up units to cancel until the
only unit left is the desired unit, or what you
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '08
 PREZHDO
 Chemistry, Imperial units, United States customary units, conversion factor, Centimetre gram second system of units

Click to edit the document details