Dimensional Analysis


What is dimensional analysis and how can we use it to help us solve problems in chemistry?

 

Dimensional Analysis for Party Planning…

If you have every planned a party, you have used dimensional analysis. The amount of beer and munchies you will need depends on the number of people you expect. For example, if you are planning a Friday night party and expect 30 people you might estimate you need to go out and buy 120 bottles of beer and 10 large pizza's. How did you arrive at these numbers? The following indicates the type of dimensional analysis solution to party problem:

Finally, in going to buy the beer, you perform another dimensional analysis: should you buy the beer in six-packs or in cases?

Realizing that carrying around 20 six packs is a real headache, you get 5 cases instead.

 

In this party problem, we have used dimensional analysis in two different ways:

 

First, let's take a look at dimensional analysis as it relates to converting units:

beers * (six pack/beer)

beers * (six pack/beer) = beers * (six pack/beer) = six pack

 

How can we use dimensional analysis to be sure we have set up our equation correctly?

 

Next, let’s take a look at dimensional analysis as it relates to calculations:

 

Another example

In fact, these are the units of a Pascal (Pa), a measure of pressure

 

In summary…


 1998 Dr. Michael Blaber