Sunday, October 2, 2016

6 Steps to Help Your Students Master Sig Figs

Call me crazy...but I LOVE teaching sig figs (aka significant figures)!  I'm not sure why I do, but I do.  It could be the challenge that goes along with trying to get students to understand how to use them and why to use them.  Or maybe it is just my obsession with numbers and data.  No matter the reason, I find it fun! You can even teach them in 6 simple steps.

Step 1: Show them why you use them

After a few years of struggling to teach the concept of significant figures, I realized that the students didn't understand why they were being asked to use them. Consider the number 3.00. Because of their math background, they ask "Can't I just say 3?". When you answer "No!", they don't get it. It's the same, right? To them it is, so we must teach them that in science, it isn't. Show them significant figures using any measurement tool (like a digital balance). Measure the mass of an object. If the tool shows the mass of the object to equal 2.1 grams, ask them if we would report the mass of the object as 2.11134 grams? It helps them to see that we can't report measurements to any more precision than they have. You can also use a POGIL to introduce the topic. It's a way to FLIP the topic. It served the same purpose but it guided their discovery of why we use significant figures. It worked well!  NOTE:  You may notice that this section is longer than the others.  That is because I strongly feel that this is the MOST important part.  If the students understand why significant figures are used, they are more open to the idea of using them.   

Step 2: Teach the rounding rules

I like to start out with the rules for identifying what makes a number significant and the rounding rules. Baby steps! Go through each rule and give examples. 

Step 3: Practice makes perfect

Give them an assignment that helps them practice identifying the number of significant figures in a piece of data. Also allow them to practice rounding to various numbers of significant figures...1 sig fig, 2 sig figs, 3 sig digs, etc. 

Step 4: Teach the rules for the operations

Remind them of the report data and measurements to the appropriate number of significant figures. Now, teach them the rules for the basic mathematical operations (addition, subtraction, multiplication, and division). 

Step 5: Practice makes even more perfect

Practice with it all together. Give them an assignment to complete (or multiple assignments if your students are like mine)  in which they have to perform the operations and report their answers to the appropriate number of significant figures. Or, create a lab in which they take measurements and report their answers correctly.     

Step 6: Assess your students' understanding

End your lesson with an assessment that measures their mastery. Give them a task or test!  These are some of the Significant Figures activities and assessments I use.

What are your best tools for teaching sig figs?