Chapter 1 Science Skills

Scientific Notation In science it is very common to work with really large or really small numbers. 602,000,000,000,000,000,000,000 6.02 x 1023 atoms = 1 mole of a substance _____ x 10 (# of decimal places) (+….moved left) Number between (-…..moved right) 1 and 9

Rules for Scientific Notation If the original number is larger than 1, then you move the decimal to the left and your exponent will be positive. 1. 4135 = 4.135 x 103 * Moved the decimal point 3 places to the left. If the original number is less than 1, then you move the decimal point to the right and your exponent will be negative. 2. .00179 = 1.79 x 10-3 *Moved decimal point 3 places to the right.

If you take a number out of scientific notation look at the exponent first. Negative Exponent = move to the left Positive Exponent = move to the right

Try These: A. 43,812g = B. .000000943m = C. 5.66 x 10-3 L = D. 7.254 x 106 g = 4.3812 x 104 9.43 x 10-7 .00566 7,254,000

Uncertainty in Measurements Measurements are an important aspect in Chemistry. Three common measurements that we typically make are for Mass, Volume, and Temperature. When you make a measurement, write down all the numbers you can. WHY?? Measuring instruments are never completely free from flaws. Measuring always involves some estimation. (Digital-Balance or Scale-Graduated Cylinder) How do you know when a measurement is reliable?

Accuracy, Precision, and Error It is necessary to make good, reliable measurements in the lab Accuracy – how close a measurement is to the true value Precision – how close the measurements are to each other (reproducibility)

Precision and Accuracy Precise, but not accurate Precise AND accurate Neither accurate nor precise