Download Metric System

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Measurements
The Metric system was developed in France
during the Napoleonic reign of France in the
1790's.
“Weights and measures may be
ranked among the necessaries of
life to every individual of human
society…They are necessary to
every occupation of human
industry.... The knowledge of
them, as in established use, is
among the first elements of
education...”
JOHN QUINCY ADAMS - Report to the Congress, 1821
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Which other countries, besides the
U.S., do not use the metric system?
According to a survey taken many years ago, the only
other countries that have not officially adopted the
metric system are Liberia (in western Africa) and
Myanmar (also known as Burma, in Southeast
Asia).
Accurate Measurements
•Accurate=how close the measurement is to the actual
measurement.
•Be sure we can compare our measurements to other
people.
•Scientists make repeated
measurements to increase the validity
and reliability of the results.
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Accuracy vs. precision
Precision:
When taking the
same
measurement
over and over
you get the same
results.
Accuracy:
How close your
results are to the
TRUE/REAL
results
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• A Measurement system
1.must be agreed upon and
2.cannot change
Ex: The foot.
• Scale units
• Metric system
attempted to do away
with the confusing
multiplicity of
measurement
scales by reducing
them to a few
fundamental ones.
Le Systeme Internationale d’Unites
(SI)
•1960
•Based on Metric System
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Standards
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• Standards are exact quantity that people agree
to use for a certain measurement.
–Ex: The meter
–The speed that light travels in a vacuum 1/299
792 458 of a second.
–Why….This seems CRAZY!!!
–The meter Clip
Another Example of a Standard
…..The kilogram
The official
kilogram, made of
platinum-iridium,
remains in France
at the
International
Bureau of Weights
and Measures
Clip
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Le Systeme Internationale
d’Unites (SI)
•English: International
System of Units
•Each measurement
has a base unit.
SI System
•
•
•
•
Based on multiples of ten.
Examples of base units
Length
•Temperature
– Meter
-Kelvin
Mass
•Energy
– Gram
-Joule
Volume •Electric Current
-Ampere
– Liter
Time
– Second
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Prefixes
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• Prefixes are used with the base units to indicate
what multiple or fraction of ten should be used.
Multiple of BU
King Henry Died
Kilo-
Hecto- Deca-
k
h
D
1000x
100x
10x
Based on
Multiples
of TEN
Fraction of BU
Drinking Choc. Milk
BU
BASE
UNIT
•Meter
•Liter
•Gram
•Watt
•Newton
•Second
•Joule
Deci-
Centi-
d
c
m
0.01
0.001
0.1
1)
2)
3)
4)
5)
Milli-
65ml=_____L
3948g=_____kg
389.59m= ______km
0.03748 mg=_____kg(use Sci. Not.)
89304µg= _______g
Convert the Following
1) 65ml=_____L
2) 3948g=_____kg
3) 389.59m= ______km
4) 0.03748 mg=_____kg
5) 89304µg= _______g
(use Sci. Not.)
Scientific Notation: a method of writing, or of
displaying real numbers as a decimal number between
1 and 10 followed by an integer power of 10
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Distance
Meter Stick
•1m = 100 Centimeters
•1m = 1000 millimeters
1cm = 10 mm
Each line on the meter stick is a millimeter.
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Meter Stick
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The last digit in all measurements
is an estimate digit.
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Amount of matter in an object
300 +70 +3.31
=373.31g
Triple Beam Balance
Grams
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Space occupied
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Length x Height x Width =Volume
Graduated Cylinder
Volume
•Space an object occupies
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Kinetic Energy
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Temperature
Fahrenheit vs. Celsius vs. Kelvin
1714:Daniel Gabriel
Fahrenheit (16861736)
Lord Kelvin
(1824-1907)
1742, Anders
Celsius (1701-1744)
Superfridge
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Temperature Conversion
K = º C + 273
º C = K - 273
ºC
• Examples on Notes.
= (º F - 32) ÷ 1.8
º F = 1.8 ºC + 32
Temperature Conversion
Answers
1) -23 ºC
2) 66 ºC
3) 290 K
4) 328 K
5) 31.9 ºC
6) 230 ºF
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Mass per unit Volume
Density
• Density: Amount of
matter in a specific
volume.
These 2 cubes have
the same VOLUME,
but they have
different densities.
Why?
Density practice problem
• Which cylinder
has the greatest
density?
• So, if I had the same
amount of each
cylinder (1 ml), which
one would have a
greater mass??
Vol: 5 ml
Mass: 10g
Density = 2 g/ml
Vol: 25 ml
Mass: 15 ml
Density = 1.7 g/ml
Derived Units
Obtained by combining different units.
Ex: Density
Density is the amount of mass per unit
volume.
D = m/v
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Remember...
....all measurement need a unit.
TYPES OF DATA
Quantitative vs. Qualitative
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• If the data collected involve observations
without measurements or numbers, then it is
referred to as qualitative data.
• Quantitative data involves numbers or
measurements.
Significant Figures
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The number of significant figures is the number of
digits believed to be correct by the person doing
the measuring.
For measured numbers, significant
figures relate the certainty of the
measurement.
As the number of significant
figures increases, the more certain
the measurement.
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Your answer cannot be more
accurate than the equipment
used to make the measurement.
The accuracy of the result is
limited by the least accurate
measurement.
Sig Fig Rules
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• Nonzero digits are always significant
• All final zeroes after a decimal point
are significant
• Zeroes between two other significant
digits are always significant
• Zeroes used solely as placeholders are
NOT significant
• Zeroes between a decimal point and a
nonzero digit are significant.
•
1)
2)
3)
4)
5)
6)
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Examples
The significant zeroes in these
measurements are colored black and
the insignificant zeroes are red.
0.0860
1.0030
0.000010203
18,000
18,000.00
0.10001
Want to make
it easier?????
Put it in
Scientific
Notation.
Practice
How many Sig Figs?
1.
2.
3.
4.
5.
6.
7.
234.87
38302.00
3900.00
0.00045
9394000.09
479301820
0.00034440
_____
_____
_____
_____
_____
_____
_____
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Arithmetic
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• When you perform any arithmetic
operation, it is important to
remember that the result can never
be more precise than the least
precise measurement.
Addition or Subtraction
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1. Perform the operation.
2. Round off the result to correspond to the
least precise value involved.

(fewest # of decimal places)
3. Example:
24.686 m + 2.343 m + 3.21 m = 30.239 m
**You will report the correct
calculated answer as
30.24 m.
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Multiplication & Division Rules
1. Perform the operation.
2. Round off the result to correspond to
the number with the LEAST number of
significant figures.
3. Example:
3.22 cm x 2.1 cm = 6.762 cm2
**Reported answer:
6.8 cm2
Practice
1)
2)
3)
4)
5)
6)
7)
8)
9)
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6.201 cm + 7.4 cm + 0.68 cm + 12.0 cm =
1.6 km + 1.62 m +
1200 cm =
8.264 g - 7.8 g =
10.4168 m - 6.0 m
=
12.00 m + 15.001 m =
131 cm x 2.3 cm =
5.7621 m x 6.201 m =
20.2 cm / 7.41 s =
40.002 g / 13.000005 ml =
Dimensional Analysis
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• Problem-solving method that uses the fact
that any number or expression can be
multiplied by one without changing its value.
• Examples:
–
–
–
–
–
Convert 50.0 mL to liters.
How many centimeters are in 6.00 inches?
Express 24.0 cm in inches.
How many seconds are in 2.00 years?
Convert 75 g/ml into kg/L
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Practice
1) How many millimeters are present in 20.0 inches?
2) Convert 45.3 cm to its equivalent measurement in mm.
3) How many feet are in 2 km?
4) How many mm are in 1 mile?
5) How many µg are in 10 lb?
6) Convert 18297 cm to miles.
7) Express 17 g/ml in kg/L.
8) Change a speed of 72.4 miles per hour to its equivalent in meters per
second.
9) Express 267 miles/hr in m/s
10) Convert 0.0598 mg/cm3 to g/cm3
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