Significant Figures — Rules & Importance

Sometimes, you'll be asked to round with significant figures. Significant figures have to do with the number of digits known with a degree of certainty. Keeping track of this number is important when gathering data from an experiment because it minimizes error. Thinking back to the scientific method we use when designing experiments, it's important that we record our observations with as much precision we can, which is where sig figs play a role. SI base units also have set significant figures rules.

##Here are the rules for significant figures:

$1.$ All nonzero digits are significant.

$2.$ All zeroes between nonzero digits are significant.

$3.$ Trailing zeroes to the right of a decimal point are significant.

$4.$ Leading zeroes to the left of the first non-zero number are not significant.

##Here are some examples. Can you see which rule applies?

1.23 has 3 significant figures

1001 has 4 significant figures

2.03 has 3 significant figures

0.033 has 2 significant figures

0.20 has 2 only significant figures

(Video) Significant Figures Step by Step | How to Pass Chemistry

by Melissa Maribel

Significant figures (or "sig figs") tell us how accurate a measurement is. When doing problems in chemistry, it's important to pay attention to the number of sig figs in a problem so that you can report that same number back in the final result.

Sounds confusing? Don't worry. Melissa explains the concept of significant figures and all the rules here in this video. You'll also get a chance to practice with her on a variety of example values and numbers written in scientific notation.

What are Significant Figures?

Significant figures or sig figs are the digits in a quantitative measurement. Sig figs are important in every branch of chemistry when measuring solutions, calculating values like theoretical yield, and converting units. Sig figs are important because they describe the amount measured, which is important to describe accurately.

Examples of Significant Figures

Importance of Significant Figures

When measuring a substance such as the mass of a solid, it is important to know the sig figs. Every scientific measuring device such as a balance, flask, syringe, and more have an individual accuracy of the measuring device. A burette is a commonly used piece of chemical glassware for measuring volumes. Typically, burettes can measure accurately to the hundredths. This means if 25 mL of a liquid are measured, the correct volume with significant figures is 25.00 mL.

Exact numbers, like the number of people in a room, have an infinite number of significant figures.

Significant Figures in Calculations

Sig figs of initial values affect the number of sig figs in a calculated value. The number of sig figs in an initial measured value are used in determining the number of sig figs in the final calculated value. Addition and subtraction rules differ from multiplication and division.

To reiterate, many measured values have an individual significant figure level based on the instrument being used. However, there are values where significant figures are not necessary like boiling points, densities, and constants. When we do other calculations, like metric conversions or stoichiometry that are necessary for key scientific processes, like making a buffer solution, sig figs are integral.