Measurements Via http://antoine.frostburg.edu/chem/senese/101/measurement/slides/sld002.htm

The Differences Numbers Measurements Mathematics is based on numbers Science is based on measurements All measurements have Magnitude Uncertainty units Numbers Mathematics is based on numbers Exact numbers are obtained by Counting Definition

Base SI Units Quantity Base Unit Symbol Length Meter m Mass Kilogram Le Systéme Internationale (SI) units are standard in science Quantity Base Unit Symbol Length Meter m Mass Kilogram kg Time Second s Temperature Kelvin K

Derived Units Area Length x length m2 Velocity Length/time m/s Density Built from base SI units Area Length x length m2 Velocity Length/time m/s Density Mass/volume Kg/m3

Very Large Units G (giga) means “one billion of” M (mega) means “one million of” k (kilo) means “one thousand of”

Very Small Units c (centi) means “a hundredth of” m (mili) means “a thousandth of” μ (micro) means “a millionth of” n (nano) means “a billionth of” p (pico) means “a trillionth of”

Significant Figures Definition: digits up to and including the first uncertain digit 1.15 mL implies 1.15 + 0.01 mL Counting significant digits Convert to scientific notation Disappearing zeros just hold the decimal point – they aren’t significant

Strategy for Unit Conversion Problems How many liters of gasoline do you have to buy to fill a 15 gallon tank? Steps: Identify the destination, including units Choose a starting point List the connecting conversion factors Multiply starting measurement by conversion factors Does the answer make sense?

Common Variation Series of conversions How many seconds in a year