Dimensional Analysis

In chemistry one must have the ability to solve problems, many problems are unit conversion problems. Using units as a guide to solve problems is called Dimensional Analysis. When students start the course this is the second topic (sig figs are the first) that must be  conquered in order for you to excel in this course.  Now in the textbook the general problem solving technique tells you to start with the given quantity to find the required unit.

For Example:  Convert 1.76 yards to centimeters

1.76yds X 1m/1.094 yd X 100cm/1m = 161 cm

During the time when I was a student in chemistry my professor said ALWAYS START WITH WANT YOU WANT TO GET i.e. start the problem with whats required. This has been my method of solving problems for years, now that I am in the teaching position what do I teach my students? My high school students take my chemistry course over the summer before there fall semester begins and i know that there  curriculum will groom them to start with the given unit. And this method often times leads to confusion therefore I must stay true to my inner chemistry self and teach them the old school method.

For Example: Convert 1.76 yards to centimeters

100cm/1m X 1m/1.094 yd X 1.76 yd= 161cm

That just feels so much better!!


2 thoughts on “Dimensional Analysis

  1. This is an excellent idea. It forces students to keep track of the solution they are working to obtain. I’m looking forward to reading more blogs!!!

  2. I’ve been using the given information approach, but always looking at the required result first, so start to finish and build the bridge in between. This result first approach is a great strategy too! Gets students to think units first, numbers later. Thanks!

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