STC_Dimensional Analysis Lesson

Dimensional Analysis

From your first year chemistry course you should already be familiar with the method we use to convert one unit to another. This can be referred to by many different names: 

Dimensional Analysis

Factor-Label Method

Conversion Factors

Some teachers will even refer to these as bridges, railroad tracks, picket fences, etc. These all work on the same mathematic principle, the identity property. This states that any number multiplied by 1 is that same number. The way dimensional analysis works is by thinking of this number "1" in different ways in order to change one unit into another unit.

Here are some different ways we can write the number 1. 1 day / 24 hours 1 1000 mL / 1L = 1 1 year / 365 days 1 We call these conversion facts. We could flip each of these facts over and they would still be correct (as long as we keep the number with the correct unit)! 24 hours / 1 day 1 1 L / 1000 mL = 1 365 days / 1 year = 1 Remember that a number divided by itself equals 1. So, as long as the top and bottom are equivalent, you can use this fact to perform dimensional analysis.

Watch the following video to show you this method. You will need YouTube access.

Remember to always start with "? unit, chemical" that you are trying to solve for. This may seem like an unnecessary step, but it is crucial. If you don't write down your question, you won't know when to stop your conversion. And, you may forget where you were headed in the problem, especially if it is a particularly long problem.

Here is an important handout on dimensional analysis.

The following video will go through the first two problems with you.

Remember to work on the module practice problems as you complete each section of content.  

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