Precision Precision measures the reproducibility of your value. Precise means “repeatable, reliable, getting the same measurement each time.”
Accuracy Accuracy is the extent to which a measurement approaches the true value. Accurate means "capable ofproviding a correct reading or measurement." A measurement is accurate if it correctly reflects the size of the thing being measured.
Measurements All of our measurements must have units on them. The SI system is used Use the metric system Mass is in grams (g) Length is in meters (m) Volume in liters (L)
Temperature A measure of the average kinetic energy of the particles in the sample The SI unit is Celcius (C) TF = 1.8tC + 32
Taking Measurements Always estimate one digit passed the last readable digit This shows the uncertainty in our measurements
Significant Figures When a measurement is recorded only those digits that are dependable are written down.
Rules for Counting Sig Figs Nonzero integers always count as significant figures 3456 has 4 sig figs. Leading zeros are never significant 0.000757 has 3 sig figs Captive zeros always count as significant figures 16.07 has 4 sig figs Trailing zeros are significant only if the number contains a decimal point. 9.300 has 4 sig figs
Mathematical Operations and Sig Figs (+) and (-) : # sig figs in the result equals the number of decimal places in the least precise measurement. 6.8 + 11.934 = 22.4896 22.5 (3 sig figs) (x) and (÷) : # sig figs in the result equals the number in the least precise measurement used in the calculation. 6.38 2.0 = 12.76 13 (2 sig figs)
Scientific Notation Allows easy conversion from decimal form to powers of 10 Always have one number before the decimal 4567 = 4.567x103 0.000345 = 3.45x10-4 The number after the 10 tells you how many spaces to move the decimal to the left or right Shows how many of the numbers are significant