Measurements

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• Measurements

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The Metric system was developed in France during
the Napoleonic reign of France in the 1790's.
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• Weights and measures may be ranked among the
  necessaries of life to every individual of human
  societyThey 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?
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STAT FACT

• 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).

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Accurate Measurements
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• Accuratehow 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
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Precision When taking the same measurement over
and over you get the same results.
YOU CAN BE PRECISE BUT STILL BE WRONG.
Accuracy How close your results are to the
TRUE/REAL results
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• A Measurement system
• must be agreed upon and
• cannot change
• Ex The foot.

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• Scale units?
• Metric system attempted to do away with the
  confusing multiplicity of measurement scales by
  reducing them to a few fundamental ones.

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Le Systeme Internationale dUnites (SI)
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• 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

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Another Example of a Standard ..The kilogram
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• 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 dUnites (SI)
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• English International System of Units
• Each measurement has a base unit.

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SI System
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• Based on multiples of ten.
• Examples of base units
• Length
• Meter
• Mass
• Gram
• Volume
• Liter
• Time
• Second

• Temperature
• -Kelvin
• Energy
• -Joule
• Electric Current
• -Ampere

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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
Fraction of BU
King Henry Died Drinking Choc.
Milk
Kilo-
Hecto-
Deca-
BU
Deci-
Centi-
Milli-
k
h
D
d
c
m
BASE UNIT
0.1
0.01
0.001
1000x
100x
10x

• Meter
• Liter
• Gram
• Watt
• Newton
• Second
• Joule

1. 65ml_____L
2. 3948g_____kg
3. 389.59m ______km
4. 0.03748 mg_____kg(use Sci. Not.)
5. 89304µg _______g

Based on Multiples of TEN
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Convert the Following

1. 65ml_____L
2. 3948g_____kg
3. 389.59m ______km
4. 0.03748 mg_____kg (use Sci. Not.)
5. 89304µg _______g

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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Laboratory Apparatuses for making Measurements
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Distance
LENGTH
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Meter Stick
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Length Distance

• 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
MASS
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Triple Beam BalanceGrams
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300 70 3.31 373.31g
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Space occupied
VOLUME
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Length
width
Height
Length x Height x Width Volume
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Graduated Cylinder
Volume

• Space an object occupies

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Kinetic Energy
TEMPERATURE
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TemperatureFahrenheit vs. Celsius vs. Kelvin
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1742, Anders Celsius (1701-1744)
Lord Kelvin (1824-1907)
1714Daniel Gabriel Fahrenheit (1686-1736)
Superfridge
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Temperature Conversion
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K º C 273 º C (º F - 32) 1.8
º C K - 273 º F 1.8 ºC 32

• Examples on Notes.

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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
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DENSITY
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Density

• Density Amount of matter in a specific volume.

These 2 cubes have the same VOLUME, but they have
different densities. Why?
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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
Vol 25 ml Mass 15 ml
Density 1.7 g/ml
Density 2 g/ml
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Derived Units
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• 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.

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TYPES OF DATAQuantitative 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.

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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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33.2

• 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.

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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.

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Examples
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• 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.
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PracticeHow many Sig Figs?
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1. 234.87 _____
2. 38302.00 _____
3. 3900.00 _____
4. 0.00045 _____
5. 9394000.09 _____
6. 479301820 _____
7. 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.

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Addition or Subtraction
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• Perform the operation.
• Round off the result to correspond to the least
  precise value involved. 
• (fewest of decimal places)
• 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
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• Perform the operation.
• Round off the result to correspond to the number
  with the LEAST number of significant figures.
• Example
• 3.22 cm x 2.1 cm    6.762 cm2   
• Reported answer
• 6.8 cm2

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Practice
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• 1) 6.201 cm   7.4 cm   0.68 cm  12.0 cm   
• 2) 1.6 km      1.62 m       1200 cm     
• 3) 8.264 g   -   7.8 g      
• 4) 10.4168 m   -   6.0 m      
• 5) 12.00 m     15.001 m     
• 6) 131 cm  x  2.3 cm     
• 7) 5.7621 m  x  6.201 m    
• 8) 20.2 cm  / 7.41 s     
• 9) 40.002 g  / 13.000005 ml   

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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
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• 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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