Using Significant Figures

Zeros between significant numbers are significant. (Example 1002—Both zeros are significant.) 

Leading zeros (before significant numbers) are not significant (before or after the decimal). (Examples 0.51 and 0.000007—None of these zeros are significant.) 

For numbers tliat are written in scientific notation, only the root portion of the number is considered. (Example 1.605 x 10 would have 4 significant digits.) 

---

Here are some standard rules for writing and using significant figures. 

A good portion of the AP Chemistry Test deals with calculations, either with or without the aid of a calculator. For all of these problems, there are two different components—the chemistry component and the math component. Most of this book is devoted to a review of the chemistry component of the problems, but this chapter is designed to review a few important mathematical skills that you will need to know as you work through the problems. Three skills that are critical to success on the AP Chemistry Test use significant figures, scientific notation, and dimensional analysis. 

Also notice that Figure 3 shows that the sum of the mass of the chlorine molecule and the mass of the phosphorus trichloride molecule is slightly smaller than the mass of the phosphorus pentachloride molecule. This difference is the result of rounding off and of correctly using significant figures. 

If you need help with graphing or with using significant figures, ask your teacher. 

Use significant figures and rounding to reflect the certainty of data. 

The following rules determine how to use significant figures in calculations that involve measurements. 

To learn to indicate a measurement s uncertainty by using significant figures... 

Calculate the volume and density for each sample and the average density of the six samples. Be sure to use significant figure rules. 

In lab you report a measured volume of 128.7 ml of water. Using significant figures as a measure of the error, what range of answers does your reported volume imply Explain. 

Use significant figures, scientific notation, and SI units in calculations. (Section 1.5)... 

Using significant figures in calculations Given an arithmetic setup, report the answer to the correct number of significant figures and round it properly. (EXAMPLE 1.2)... 

Another way to indicate uncertainty is to use significant figures. The number of significant figures in a quantity is the number of digits that are known accurately... 

---