"Unit Factoring" is also called "Dimensional Analysis" or the "Factor Label" method. It is useful when converting from one set of units to another, when changing units in a rate, or when doing stoichiometry. Here are some online resources that might help you if you are still stuck on some aspect.
Remember, working a "Level 4" Problem means YOU can determine conversion factors AND choose and place the correct conversions to answer your question.
----------------------------------------------------
HINTS:
If your START substance and END substance are DIFFERENT SUBSTANCES, you will need a mole-mole ratio.
If you have grams (MASS) anywhere in the problem, you will need a PERIODIC TABLE and a molar mass.
If you have Liters (VOLUME) of a gas, you will need the 1 mol __ = 22.4 L __ conversion factor (thanks, Avagodro).
----------------------------------------------------
TO SOLVE:
Moles of A to Grams of A: one step, molar mass from periodic table
Grams of A to Moles of A: one step, molar mass from periodic table
Moles of A to Moles of B: one step, mole-mole ratio**
Grams of A to moles of B: more than one step, using molar mass from periodic table and mole-mole ratio**
Moles of A to Grams of B: more than one step, using mole-mole ratio and molar mass from periodic table**
Grams of A to Grams of B: at least three steps, using molar mass from periodic table, mole-mole ratio, and another molar mass from periodic table **
**There are times when more than one mole-mole ratio is needed in the middle of a problem.
-------------------------------------------------------
VIDEOS AND RESOURCES WHICH MIGHT BE HELPFUL TO SOME STUDENTS:
Unit Factoring Basic Problem (one version) (11:13)
http://www.youtube.com/watch?v=DsTg1CeWchc
Stoichiometry lesson by Bozeman Science (9:45)
https://www.youtube.com/watch?v=LQq203gyftA
Stoichiometry by Crash Course in Chemistry (12:46) "Stoichiometry: Chemistry for Massive Creatures - Crash Course Chemistry #6"
https://www.youtube.com/watch?v=UL1jmJaUkaQ
Lecture covering the process of "Moles A to Moles B and Grams A to Grams B Stoich" (11:38) Several examples are written out and narrated step by step.
https://www.youtube.com/watch?v=k8uUBs9r4p0
How to Understand Conversion factors by Tyler Dewitt (10:13) Emphasizes the rationale behind the mechanics of what we are doing
https://www.youtube.com/watch?v=HZ9weUkSdoY
Still want more? Try these search terms:
- stoichiometry
- unit factoring
- factor label method
- dimensional analysis
- how to convert grams to moles
- how to convert grams of A to grams of B
- molar mass
- mass ratio
- balanced equations
- conversion factor
(You may also find additional video links when watching any of the above videos.)
How to Determine MOLE RATIOS
Lecture style with board notes (5:37)
https://www.youtube.com/watch?v=42Mk1B2u0hk
How to Calculate MOLAR MASS
Step by step (8:49)
https://www.youtube.com/watch?v=guAbb_yBSfs&nohtml5=False
Slow paced (3:00)
https://www.youtube.com/watch?v=F9NkYSKJifs
Some other links/videos
For help with metrics using the same format, try this site: http://www.youtube.com/watch?v=w0nqd_HXHPQ&feature=related
For basic help with metrics, try this http://www.youtube.com/watch?v=SYkmadc2wOI&feature=fvwrel (But you still have to memorize the prefixes!!!)
Here is another series covering similar material: http://www.youtube.com/watch?v=Vyr20KfKKU4&feature=related
For an advanced example of unit factoring in the real world... http://www.youtube.com/watch?v=ScvuRb6vsz4&feature=relmfu
And finally, for stoichiometry (there's that word again!), look at this example...http://www.youtube.com/watch?v=eQf_EAYGo-k&feature=relmfu
Happy Factoring!