
CP Sci 9 1st Sem. Gen Chem  1st Sem. 
Working With Numbers: Objectives: 1. Define significant digits. 2. Explain how to determine which digits in measurement are significant. 3. Convert measurements in to scientific notation. Key Terms: significant digit percent error density Web Resources:
Notes: Significant Digits: The purpose of significant digits is to limit the amount of uncertainty in the data you display. The measured and the estimated digits of a measurement are considered significant. (example: If you look at the picture the significant digits would be read as 26.45g. 26.4 measured, .05 estimated) Rules: 1) Zeros that simply hold places are not significant. A) No decimal point. Example: 1050
B) With a decimal point. Example: 0.001050
2) If numbers are on both sides of the decimal point, all are significant. Example: 21.00356
Significant Digits In Calculations: Rules:
Example: 120.0 * 0.0030 * 150.004 =
Example: 420.1 + 3501 + 0.1123 + 1.2 =
Scientific Notation: Scientific notation is a way that scientists make that incredibly large numbers used in science easier to work with. There are 602,000,000,000,000,000,000,000 atoms in a mole of a substance. It is much easier to use the answer as 6.02 x 10^{23}. Rules: 1) The answer must retain the correct amount of significant digits. 2) If the size of the number is to be reduced the exponent will be positive. Example: 398700 = 3.987 x 10^{5 }(the exponent is equal to the number of times that the decimal point was moved) 3) If the size of the number is to be increased the exponent will be negative. Example: 0.00501 = 5.01 x 10^{3}
Percent Error & Percents: Percent error calculations are used to compare test results to a known accepted quantity. The formula is as follows: Percent error = ((measured value  accepted value) / accepted value ) * 100% Note: The result can be positive or negative but the answer is always represented as the absolute value

Last modified: September 05, 2004 