Units of Measurement

1
Units of Measurement

• Chapter 1

2
Measurement

• SI (metric) system vs. English system
• Temperature
• Celcius vs. Fahrenheit
• Length
• meter vs. foot, yard, mile
• Volume
• Liter vs. cc, cup, pint, quart, gallon
• Note 1cc 1mL 1cm3
• Mass
• Gram vs. ounce, pound

3
Metric Prefixes
(Table 1.1 p.4)

• For the same base unit
• Mega M 106 10 x10x 10 x10 x10 x10
• Kilo k 103 10x10x10
• Hecto h 102
• Deka da 10
• O (base) 1
• Deci d 10-1 1/10
• Centi c 10-2 1/10 x 1/10
• Milli m 10-3
• Micro m 10-6
• Nano n 10-9
• Kids Have Dropped Over Dead Converting Metrics

4
Exponential Numbers

• Write 3 x 10-4 as a common number
• Write 350000 as an exponential number

5
Problems

• How many meters in 20mm?
• Three ways to do this problem
• KHDODCM
• Factor method
• Memorize conversion
• How many g in 4kg?

6
How to convert between units (the factor label
method)

• Pay attention to the units. Notice where youre
  starting and where you need to end up.
• Find a conversion factor that relates the units
  in 1.
• Mathematically use the conversion factor so the
  proper units cancel and you end up with the unit
  youre interested in.

7
Try it.

• How many pounds in 42.6kg?
• (There are 2.2lbs in 1 kg.)
• Conversion factors will be given on exams.
• 42.6kg x 2.2lbs/1kg 93.72 lbs
• Why not 42.6kg x 1kg/2.2lbs ?

8
Try on your own

• How many feet are in 16.5 yards?
• 3 feet 1 yd.
• A harder one
• If my car gets 25mi/gal,what is it in km/L? 1gal
  3.8L, 1.68 mi 1km

9
What numbers are significant?

• Any number other than zero is significant.
• Zero may or may not be
• Zero Is significant when-
• Zeros within a number 2.203
• Zeros at the end of a number with a decimal 1.30
• Zero is not significant when -
• Its at beginning of number 0.33 or 0.0033
• Maybe
• At the end of a number without a decimal 3,000.
• Yes if 29991, No if 2000 1000

10
Rounding

• Last digit less than 5, round to 0.
• ex. 1.234 is 1.23
• Last digit 5 or more, round up.
• ex. 1.235 or 1.238 are both 1.24

11
Significant Figures in Calculations

• Addition / Subtraction
• Same number of decimal places as term with fewest
  decimal places
• 15 1.75?
• Multiplication / Division
• Same number of significant figures as term
• with the fewest sig. figs.
• 10.0 x 1.23 ?

12
Putting it all together

• How many grams are in 1.62 lbs?
• 2.2lbs 1kg Express your answer to the proper
  number of sig. figs.

13
Temperature Conversions

• Temperature is a measure of energy.
• What temperature does water freeze?
• 320F, 0oC, 273K
• What temperature does water boil?
• 212oF, 100oC, 373K
• What is the lowest possible temperature?
• -459oF, -273oC, 0K
• How to convert between these units?
• F 9/5C 32 or C5/9(F-32) or K C273

14
Try it

• Convert body temperature, 98.6F to C and to K.

15
Density

• Density mass/volume
• Units are g/mL
• If density of water is 1 g/ml and oil is 0.8
  g/ml, which liquid will be on top?
• Will density increase, decrease, or stay the same
  if we increase
• temperature?

16
Why density is important

• Urine test
• High density could indicate diabetes melliltus
  (high blood sugar)
• Low density could indicate diabetes insipidus
  (kidney cant concentrate urine)
• Bone density
• Decreased bone density is associated with
  osteoperosis
• Brix test
• Density decreases as fermentation progresses

17
Try it

• A rock has a a mass of 1.075g and a volume of
  3.345ml. What is the density of the rock?
• A 335cc sample of urine has a mass of 342.6g.
  What is the density?