Significant Figures (sig figs) How do you know when numbers are significant figures?
Covered in this Lesson This lesson will explain what significant figures are and why they are important. Significant figures are the digits that represents the accuracy an experimental measurement is known to be (ACS, 2006).
Why Sig Figs? In science the numbers we use are most often from measurements Each device may have a different degree of accuracy; some measure to the ones, other to the tenths and so on. The numbers you record using your measuring device are the sig figs.
Significant Figures (sig figs) Determining sig figs depends on a decimal point. There are two main rules: Numbers without a decimal point. Numbers with a decimal point.
Rule: Without a Decimal If there is NO decimal point in the number, count all non-zeros digits and zeros between the non-zero digits. non-zero digits 80,903,000,000 zeros between zeros not significant This number has 5 sig figs.
Examples: Without Decimal Points Example 1: 7000 L The only non-zero digit is 7 and zeros are after the 7, there is only 1 sig fig. 7000 (1 sig figs) Example 2 204500 km The non-zero digits are 2, 4, 5 there is one zero between, there are 4 sig figs 204500 (4 sig figs)
Rule: With a Decimal If there is a decimal point in the number, go to the first non-zero digit and count all non-zero digits and zeros after. These zeros are not significant 0.0000003410 1st non-zero digit the rest of the digits are significant This number has 4 sig figs
Examples: With Decimal Points Example 1: 0.103 L The first non-zero digit is the 1 and there are two more digits for a total of 3 sig figs 0.103 L (3 sig figs) Example 2 6.08500 km The non-zero digit is before the decimal point so all digits are significant. 6.08500 km (6 sig figs)
Practice Problems 711 kg B. 8.4745 cm C. 5.600 L D. 1,000,000 g E. 0.00045 Mm F. 0.000200 mL G. 901,001 ng H. 100100 s
Answers Practice Problems 3 sig figs B. 5 sig figs 4 sig figs D. 1 sig fig E. 2 sig figs F. 3 sig figs G. 6 sig figs H. 4 sig figs