When chemists do experiments, they make measurements. These measurements generally involve the reading of a graduated scale. It is common practice to read a graduated scale as accurately as possible. Thus in making a reading
All of the digits that are certain plus the one that is uncertain are referred to as significant figures.
first use the lines, and
then guess the last digit by reading between the lines.
then guess the last digit by reading between the lines.
Using the ruler graduated in mm, the length of the blue square should be recorded as 16.2 mm or 16.3 mm. The last digit is a guess, but it is assumed by others who read the measurement that the last digit is uncertain, and that the actual value is 16.2 ± 0.1 mm.
All of the digits that are certain plus the one that is uncertain are referred to as significant figures.
The 16.2 mm measurement above has three significant figures.
When these measurements are used in calculations it is important to report answers to the correct number of significant figures so that anyone reading the work will know how accurately the measurement was made.The first step in doing this is to recognize how many significant figures are in a given number.
The number of significant figures in a measurement is the number of digits after the first non-zero digit. Therefore leading zeros are not significant, but trailing zeros are significant as shown in the examples below.
The number of significant figures in a measurement is the number of digits after the first non-zero digit. Therefore leading zeros are not significant, but trailing zeros are significant as shown in the examples below.
2.34 has three significant figures.
0.0234 has three significant figures.
2.340 has four significant figures.
0.0234 has three significant figures.
2.340 has four significant figures.