4 surprising reasons you should teach significant figures (and 1 not-so-surprising reason)

I am going to poke the hornet’s nest.  Hear me out. 

You should teach significant figures at the beginning of chemistry. 

There.  I said it.  You should teach sig figs.  There are so many differing opinions on this topic.  Just read the comments of any sig fig post.  Some are adamant that industry hasn’t used them for years.  Others say every measurement in their research lab must use them.  Teachers will say their kids will miss the point forever.  Others say they are preparing them for real scientific work.

I am going to seem to contradict myself here.  Both sides of the argument are right.  I know in today’s culture that is hard to understand.  But both are right.  Therefore, the reasons I list below as why to teach significant figures are going to be different than most.

Significant figures make students think about math processes.

This might be shocking to you, but many students today don’t actually think about math.  They just snap a photo to ChatGPT for homework and then blindly trust their calculator in class.  Applying significant figures slows the student down and forces them to think about what is really happening in their math process.  Even though it can be hard to teach at first, students who understand the sig fig math rules are pausing to consider what happened in a calculation.  That moment of pause can lead to … critical thinking.  And if my students leave my room having taken a few moments to think critically about math processes, then they are better for it.

Significant figures teach students to be skeptical.

The reason for belief in many students in this generation is because the internet said so.  Blindly accepting things that that they saw on TikTok doesn’t always lead to good scientific thinking.  Teaching significant figures adds attentiveness to measurements that they didn’t have before.  And that creates better thinking overall. 

Here is an example.  I saw this post on the internet.  It was talking about how close the homerun derby in the MLB was.  And it was really close!  So close in fact, they flexed showing how precise their digital measuremnt system was.  The measurements were recorded to the one ten billionths of a foot.  Wow.  That is very precise.  If that measurement was truly recorded using significant figures, that means that MLB is using a device that can measure the flight of a baseball that is discerning distance down the subatomic level. 

I hope that students will learn to be skeptical about measurements like that.  And the primary way they learn to be skeptical is with sig fig training.

Significant figures teach students to communicate precisely.

Over the past 25+ years of teaching, I have seen some wild numerical answers.  Some kids truncate numbers in their communication so severely that the numbers almost lose definition.  Others want to write every digit ever produced by their calculator in order to feel secure.  Both demonstrate poor scientific communication.  By learning significant figures, students learn that how they communicate is important.  It really does matter how to describe measurements.  Even bigger than that, it matters how they communicate about anything!  I’m not saying that sig figs will magically transform every student into a perfect orator.  But adding sig figs into chemistry will teach them to consider what they communicate. 

And after 25+ years teaching, a teenager considering what they are saying at any level is a step up.

Significant figures actually speed up your grading.

This is going to sound very counterintuitive.  It doesn’t seem that adding another layer of grading to your grading would make you faster.  And at first, it doesn’t.  You have to slow down to help the kids learn how to communicate better.  You have to take off points when their measurements aren’t recorded as precisely as they should.  But after the sig fig unit, I find a payoff.

Here is my system.  In the sig fig unit, every number has to be exactly correct concerning sig figs.  I force it by applying plenty of points so they can’t skip it and still pass.  But on every other unit, they have to be within one sig fig of the right number of sig figs.  Is this very scientific?  Not at all.  But they the students have gained the benefits that I listed above.  Now it’s time for my benefit.  Here is how it could work.  A question on my test has an answer with 5 significant figures.  A kid dramatically rounds and only puts one sig fig.  His answer is 10,000 g.  Now I have to go look more carefully at his work to see if he knows the content that we are working on.  Let’s say that number came during the stoichiometry unit.  I have to review all of his dimensional analysis to see if he can actually do the thing I am asking him to do.  But in my system, a kid could have four to six sig figs and not lose any sig fig points.  And their answer will look much more similar to my key, which speeds up my grading of that problem.  The kids get trained over the course of the units and my grading gets faster and faster.

One final reason to teach sig figs.

Scientific measurements actually have limited precision.

This is likely the first reason you teach sig figs.  It’s the reason they exist.  And it is obviously important.  But the goal of this article was to get you thinking about other reasons for teaching the system. 

Now I have to go drive the 3.858391200401331 miles to school to teach significant figures to my kids.

Need another tool to help you teach the first unit in chemistry?  Use Metricize to help your students actually gain metric number sense.  In each board game is enough boards for 30 students to play at the same time.  You read the questions and five tables of six students will all make their best estimations of metric units.  As the teacher, you can decide what units to include.  If from simple g and m up to g/mL and km/hr.  Students have a blast!  And you get to watch their metric number sense grow as they play a fun trivia betting game.