Unit Conversions

Unit Conversions Consider units to be factors kg g x = g

Unit Conversions Relationship – a statement of equality between two sets of units 1 m = 1000 cm 1 mile = 1609 m 1 L = 1000 mL Conversion factor – a ratio of the two sets of units in a relationship Two conversion factors from each relationship

Relationships 1 m = 100 cm 1 km = 1000 m 1 m = 0.001 km 1 kg = 1000 g 1 g = 1000 mg 1 g = 106 μg 1 L = 1000 mL 1 mL = 1 cm3

SI Prefixes (www.bipm.org/en/si) 103 kilo k 10 -2 centi c 106 mega M Factor Name Symbol 103 kilo k 10 -2 centi c 106 mega M 10 -3 milli m 109 giga G 10 -6 micro μ 1012 tera T 10 -9 nano n

Use Prefixes to Remember Metric Relationships Prefixes are multiples…. 1 kg = 103 g = 1000 g 1 mg = 10-3 g = 0.001 g 1 cm = 10-2 m = 0.01 m

Steps to Performing Unit Conversions List and identify the information given (G) in the problem. List and identify the information that you want to find (F), i.e., the subject of the question(s) you are trying to answer. List any relationships or other data you need to solve the problem. Identify the units that you want to “find” and write this on the left side of the equals sign. (Identify what you are calculating!) Identify the given measurement and write this on the right side of the equal sign. Set up conversion factors to cancel 1st unit and use as needed

Unit Conversions – Things to Remember Write in all measurement units (as you write the numbers they are attached to). Be systematic and insert one conversion factor at a time. The units that you are given should cancel with the units in the denominator of the conversion factor. When the units of the “find” are in the proper places in the numerator and denominator, then compute the result Remember that any number in a numerator you will multiply. Divide by any number in a denominator. If the “find” unit has both a numerator and a denominator (such as miles per hour), both measurement units must be converted.

Units are part of the number! Every number you write down must include its units The final calculated result must include the units unless it is a unitless number You will be penalized in graded work (including lab) if you do not properly affix units!

Practice Problems