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"To the dull mind all nature is leaden. To the illumined mind the whole world burns and sparkles with light." -- Ralph Waldo Emerson

Standards of Measurement

Standard of Measurement

Concept Pages:

Physical Science "Key Concepts" Home Page

For more info on your own, check out the Yahoo! page on Measurements and Units

 

Section Review questions
Chapter review questions

    A Standard is

    • An exact quantity that people agree to use as a basis of comparison

    • All measurements are compared to the same exact quantity

    • All measurements can then be compared with one another
SI - The International System of Units
Most of the world, and science, uses the SI - International System of Units

Prefixes


Powers of 10
    • 10 = 1 x 10
    • 100 = 10 x 10, or 102, or 1 x 102
    • 1,000 = 10 x 10 x 10, or 103, or 1 x 103
    • 1,000,000 = 1 x 106
    • 0.001 = 1/1000, or 1 x 10-3

Check out Powers of Ten - an interactive site
The most common prefixes are:
Kilo - object x 1 000

deka – object x 10

 

 deci - object/10
centi - object/100
milli - object/1 000
micro - object/1 000 000
nano - object/1 000 000 000
A "Help" for choosing the correct prefix when using the three most common in introductory science:

On a 3 x 5 card, copy the following:


This can be used to trace the movement of the decimal as you change units in the SI (metric system) by factors of ten, from one unit to another.
1. Point to whichever unit your number is in.
2. Count the number of places you move, and in which direction, to get to the one you need.
3. The same number and direction applies to your new number.

Example: Change 0.0123 Kilometers to centimeters.
1. Put your pencil on the mark above "Kilo"
2. count the 5 marks to the right you need to get to "centi"
3. Count the 5 places to the right from the decimal in 0.0123 Km which will now equal 1,230cm.

Note: If you start or end with a unit without a prefix (meter, gram,Liter), start at the "1" with "units" underneath it.

 

SI Units        

Length
  • distance between 2 points
  • SI unit of length is the meter
  • metric rulers and meter sticks are used to measure length

Volume

  • amount of space occupied by an object
  • if you can measure straight sides with standard length units, you can figure volume by multiplying the outer dimensions.

e.g. (for example):
 


Volume = 2cm x 3cm x 6cm = 36cm3

Derived Units

• units that are obtained by combining SI units

Such as:

    • 1 Liter = 1dm3
    • 1 milliliter = 1cm3

 Mass
    • measure of the matter in an object
    • SI unit is kilogram
      • smaller masses may use grams or milligrams

Density


• mass per unit volume of a material

• found by dividing mass by volume

e.g.:    


Time
    • interval between 2 events
    • SI unit is seconds
      •

 Temperature

    • measure of how hot or cold something is
    • SI unit is Kelvin
    • 0 K  (say "zero Kelvin) = absolute zero
    • You will more commonly use C (Celsius)
    • 0 C° (say "zero degrees Celsius) = 273 K

Using Graphs


Graph

Line Graphs

    • used to show trends, or how the data changes over time.

  • compare table and graph showing the same data:
    •

 

 
Colorado Springs Monthly Average Maximum Temperatures
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
°C 5.2 7.0 10.0 15.4 20.3 26.1 29.1 27.3 23.1 17.5 10.3 5.6 16.4
°F 41.4 44.6 50.0 59.7 68.5 79.0 84.4 81.1 73.6 63.5 50.5 42.1 61.5

[This and the following two charts were made with Microsoft Excel]

The independent variable is shown on the horizontal axis, in this example:
    • time, the months Jan - Jun

The dependent variable is shown on the vertical axis, in this example:

    • sales in millions of dollars.

Bar Graphs

• useful for comparing data collected by counting or recording

Compare the following tables and graphs showing the same data:

 
Colorado Springs Monthly Average Maximum Temperatures
(Compare this also with the line graph above)
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
°C 5.2 7.0 10.0 15.4 20.3 26.1 29.1 27.3 23.1 17.5 10.3 5.6 16.4
°F 41.4 44.6 50.0 59.7 68.5 79.0 84.4 81.1 73.6 63.5 50.5 42.1 61.5

Colorado Springs Average Monthly Precipitation

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mm 7.5 9.0 21.9 31.5 56.8 53.5 74.0 70.2 32.6 20.8 12.8 9.5
inches 0.3 0.4 0.9 1.2 2.2 2.1 2.9 2.8 1.3 0.8 0.5 0.4

Circle Graphs

• a circle graph, or pie chart, is used to show the parts of a quantity that is considered as a whole.

compare the following table and graph showing the same data:

Colorado Springs Average Monthly Precipitation

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
2% 3% 6% 8% 14% 13% 18% 18% 8% 5% 3% 3% 100%

 

Notice! The data that is used to make this chart is limited! It is not the full range that was used in the other two examples! The pie chart can be effective only when limiting the factors that go into it.  In this example, it compares ONLY the Average of all months compared with each other.
 

Analyzing the advantages and disadvantages of universal use of SI

    Give examples of SI units already in common use in the US:

    • Medicines (1cc = 1 cm3 = 1mL)
    • 1L & 2 L water and soda bottles

Check out: "Toward a Metric America..."

Updated 10/20/07