1. 2.02 Units and the Metric System
Dr. Fred Omega Garces
Chemistry 100
Miramar College

2. Measurements
In our daily lives we deal with making measurement routinely.
i.e., How much gasoline is required to fill your gas tank? What time did you wake up this morning? How fast did you drive to school today ?
Doctors, nurses, pharmacist-
Doctors and nurses make measurement constantly. Measurements like pulse rate, blood pressure, temperature, drug dosage.
Math - The language of Science
Scientist make countless measurement during their experiment to prove or disprove theory.

3. Numbers without meaning
What is your response if I told you that
I weigh 68.5
You would either think I was mad or anorexic.
In any measurement Magnitude (the number) as well as Unit (meaning) must be stated.
Otherwise it is Meaningless (most of time)

4. System of Measurements
What units are used?
Scientific Community
The Rest of the
World
America
English System
1 ft = 12 in
1 yd= 3 ft
1 mi. = 1,760 Yd
1 mi = 5280 ft
Metric System
1 km = 1000 m
1 m = 100 cm
1 m = 1•109 nm
Le System
International d’Unites
time  sec
length  m
mass  kg
temperature  Kelvin

5. Units – gives meaning to the measurement
What are Units ?
Standards used for quantitative comparison.
i.e., Ft, mi, in, cm, mi/hr, km/min, gal, J, cal
The U.S. prefers the English Unit system.
Rest of the World
uses the metric system.

6. Metric system and the Le Systeme International d'Unites (SI)
The Metric system is convenient because it uses only one fundamental unit for each type of measurement, and all of its conversion factors are multiples of 10.
The scientific community uses an updated metric plan called the SI units.
SI (Le Systeme International d'Unites)
There are seven (7) quantities in which all units can be derived, this is the basis of the SI units; all other units are derived from these seven

7. SI units All others units are derived units
There are seven quantities (fundamental) in which all units can be derived; these are the base units and the SI defines these as:
All others units are derived units

8. Relationship of SI to SI Derived Units
Relationships of the SI units to SI derived units with special names

9. What are Derived Units ?
Derived units result from these seven base units.
i.e., vol. (L) derived from m3  meters.
energy (J) derived from N•m or (kg•m / s2) • m
pressure (psi) derived from lb. /in2 or (kg /m2)

10. Ease of conversion of the SI units
The SI units employ a series of prefix to indicate decimal fraction or multiple of units.
Prefix
Symbol
exp factor
factor
Mega M 10 6
1,000,000
kilo k 10 3
1,000
deci d 10 -1
1 / 10
centi c 10 -2
1 / 100
milli m 10 -3
1 / 1,000
micro
10- 6
1 /1 ,000,000 m
nano n 10 -9
1 / 1,000,000,000
pico p 10
-12
1 / 1,000,000,000,000

11. Metric Prefix Relationship
Consider the relationship between each metric prefix.
In using the metric system conversion factor in dimensional analysis remember to use the conversion ratio that makes sense. For example the conversion between micrograms (µg) and grams (g) is either 1 μg = 1•10-6 g or 1,000,000 µg = 1g. It is easier to use the 1,000,000 µg = 1g conversion since this conversion does not involve negative exponents.

12. Conversion within English System
In the English system, exact conversion factors must be known.
i.e., How many inches in a marathon (26 miles 385 yards)?
To solve this, must know that there are 63,360 in = 1 mile
Mile  Yard  feet  inches
To solve this problem the relationship between miles and in must be known. In fact to convert between miles, yards, feet and inches each relationship (conversion factor) must be known.
Length
1 Mi. = 1,760 yd = 5,280 ft = 63,360 in
1 yards = 3 ft = 36 in
Therefore in 26 miles, there are :

13. Conversion within Metric System.
Advantage of the metric system is that converting from one unit to the other is just a matter of multiplying or dividing by 10's.
i.e., How many centimeters in a 100 km ?
To solve this, simply need to know that kilo means 1000, therefore there are 1000m = 1 km (conversion factor) and that there are 100 cm = 1 m
Kilometers  meters  centimeters
This is very useful in science, especially when you have to work numerical problems.
Length
1 km = 1000 m, 1 m = 100 cm
Therefore 100 km is equal to:

14. English and Metric System.
In science, measurement is based on the metric system (SI).  Life in America is a bit more complicated because we live in a global world that uses the metric system but at home we use the English system.
The metric system (or SI) is very useful in science, especially when you have to work numerical problems. When dealing with the metric system the conversion is easy.
When dealing with English and metric, the conversion factor between two units must be known: i.e., 1 inch = 2.54 cm
In the automotive industry, the U.S. still uses predominately the English system. If you want a wrench for example that is the next size smaller than a 7/16 -inch, it would be logical to use 6/16-inch. The correct next lower size is actually labeled 6/16-inch. It becomes really complicated if you are looking for the next smaller size for 3/4-inch because it is not 2/4 (or 1/2-inch) it is actually 11/16-inch -go figure.

15. Other Metric relationship.
Length - distance
English
1 ft = 12 in
1 yd= 3 ft
1 mi. = 1,760 yd.
Metric
1 km = 1000 m
1 m = 100 cm
1 m = 1•109 nm
English - Metric
1 in = 2.54 cm
1 mi. = km
Volume - space
English
1 gal = 4 qt
1 qt = 2 pt
1pt = 16 fl oz.
Metric
1 L = 1000 ml
1 ml = 1 cm3 = 1 cc
English - Metric
1 gal = L
1 fl oz = ml
Mass - quantity of matter
English
1 lb. = 16 oz
1 Ton = 2000 lb.
Metric
1 kg = 1000 g
1 g = 1000 mg
English - Metric
1 lb. = g
1 kg = lb.

16. Some interesting measurements
Order of magnitude as expressed via metric measurements

17. Putting it in perspective
In class you will be assigned a conversion project. It will be up to you to make the appropriate conversion. Be prepared to make a presentation on this assignment. You can create a poster, a PowerPoint slide show or come up with something creative.
Length
English - Metric
miles - km
Volume
gallons - Liters
Mass
pounds - kg
Distance of one light year
Volume of space in universe
Mass of universe
Distance around the world.
Volume of the sun
Mass of sun, Jupiter, Earth, Moon
Distance San Diego to NY City.
Volume of earth
Mass of water in ocean
Distance SD to LA.
Volume of water in ocean
Mass of Empire State Building.
Distance Pet Co to Qualcomm.
Volume of water in great lakes
Mass of Statue of Liberty.
1000 mi to km
volume of water in Shamu's pool
Mass of average elephant.
500 mi to km
volume of water in Miramar's pool
1 ton g kg
100 mi to km
Volume of gasoline in Hummer
300 lb
60 mi to km
Volume of water in 21 gallon tank
150 lb
25-mi to km
volume of air in lungs
100 lb
10 mi to km
volume in 1 gallon
50 lb

18. Summary Measurement - Measurement
    Consist of a Magnitude (a number) and a Unit (the meaning)
Unit system - Le Systeme International d'Unites ( SI ) There are three unit systems.  The English, Metric and SI (Le Systeme International d'Unites).  The SI is derived from the metric and is more specific.
The Metric system is based on prefixes which relates the magnitude of a number to another by factors of 10. 

19. Sample Questions
1. Which one of the following measurements contains four significant figures ? a) g b) g c) g d) e4 g e) all 2. Which of the following has three (3) significant figures: a) 0.06 b) 1610 c) 1.090e3 d) e) none 3. One edge of a cube is measured and found to be 2.54 cm. What is the volume of the cube in in3. (1.00 in = 2.54 cm) a) 16.4 b) 1.00 c) 106 d) 6.45 e) none 4. How many centimeters are there in 1 kilometer ? a) 100 b) 1e-5 c) 1000 d) 1e6 e) 100, At what temperature does K = °C a) 100 b) 0 c) 273 d) Never the same e) none 6. The prescribed injection of a drug is oz. If the syringe is graduated in cubic centimeters, to what mark would you draw the drug? (29.6 mL = 1 oz) a) 5.00cc b) 0.34 cc c) cc d) 10.0 cc e) none 7. Which of the following is the largest mass? a) 41 g b) 8.2e6 microg c) 3e3 mg d) 4.1e-4 Kg e) none 8. Which is the fastest speed ? a) 100 km/hr b) 100 mi/hr c) 1e5 m/hr d) 5.2e6 ft/hr e) none

20. Sample Questions
9. The lethal dose of heroine is 150 mg per kilogram of body weight.
Estimate how many grams of heroin would be lethal for a 200-lb man.
a) 13.6 g b) 13.6 mg c) 13.6 oz d) lb e) none
10. You obtain the number on a calculator. If this number actually has four (4) significant figures, how should it be written?
a) 1251 b) c) 1.250e3 d) 1.250e-3 e) none
11. You obtain the number on a calculator. If you need to round this number to the hundredths, how should it be written?
a) 1200 b) 250 c) d) e) none
12. How many of the following numbers does not have 5 significant figures:
a) b) c) e8 d) e) all
13. The number 6.33e-2 equals :
a) b) c) 633. d) 63.3 e) none
14. When expressed in exponential notation, the number becomes:
a) 3.02e-4 b) 3.02e4 c) 3.02e3 d) 3.02e-3 e) none
15. A woman who weights 38.5 Kg is most likely to be which of the following ?
a) a basketball center b) a discus thrower c) a gymnast d) a volleyball player e) not enough info.
16. Which of the following is the shortest length ?
a) 1.21m b) 75 in c) 3 ft - 5 in d) a yard stick e) all the same