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I survived the first week in Chem !!!!
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Prefix mini- quiz
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“How do I convert between these %%&! prefix systems ?”
There are many competing choices of prefixes for a given quantity in chemistry (and physics and biology) Nobody follows the rules…… “How do I convert between these %%&! prefix systems ?” EXAMPLE Common prefix units used to define wavelength, : m nm pm mm (millimicron) Å =10-1 nm
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15 m = ??? pm
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Divide and conquer, maggot !
How to convert ??? Method 1) Algebraic (‘Marine’ way) Doc’s story about his HS chem teacher Divide and conquer, maggot !
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15 m = ___?____ pm Divide: 15 m = ___?____pm pm pm
The `Marine’ way of conversion: 15 m = ___?____ pm Divide: 15 m = ___?____pm pm pm Conquer (substitute and calculate) = ___?____ 10-12 =15*10-6-(-12) =15*10+6
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Method 2) Factor-label (commonly taught by high school teachers)
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15 m = ___?____ pm 15 m * 10-6 m m 15 m * 10-6 m 1012 pm
`factor-label’ way of conversion: 15 m = ___?____ pm 1) Convert to base units (m) 15 m * 10-6 m m 2) Convert to base units to desired units & compute 15 m * 10-6 m m 1012 pm m =15* pm =15*10+6 pm
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metric-Metric conversion problems done both ways
(on board) How many cm in 5 dm How many pg in 50 ng ? 5*101 =50 cm 50*103 pg=5*104 pg =50,000 pg
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More Guided practice Unit conversions (via factor-label & Algebraic)
answers 4.57*104 g Convert 45.7 kg to g Convert 0.73 mL to L 730 L =7.3*102 L Convert 7.2 kg/L to mg/ L 7.2 mg/L
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Convert 5.0*103 ps to its equivalent in ms
U-DO-IT !!! How many dg in 2.4 kg ? 2.4*104 dg 23 nm = ? m 2.3*10-2 m Convert 5.0*103 ps to its equivalent in ms 5*10-6 ms 6 pg/L = ?? g/mL 6*10-3 g/mL
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5 ng= _____pg ? 500 pg 5000 pg 50 pg 0.5 pg
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