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Glossary of Scientific Units
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tarix | 05.02.2018 | ölçüsü | 22,19 Kb. | | #25347 |
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Glossary of Scientific Units
Temperature Units:
Degrees Celsius (°C): Introduced by a Swedish astronomer, Andres Celsius, 1°C is defined as 1/100 of the temperature difference between water freezing point and boiling point by a pressure of 1 atmosphere. The thermometer freezing point is 0° and the boiling point is 100°.
Degrees Fahrenheit (°F): Named for the German-born scientist, Gabriel Daniel Fahrenheit, 1 °F is defined as 1/180 of the temperature difference between water freezing point and boiling point. The thermometer freezing point is 32° and the boiling point is 212°.
Degrees Kelvin (°K): Invented by William Thomson, Lord Kelvin, a 19th Century British scientist, this scale is based upon the fact that the coldest it can get (theoretically) is -273.15 degrees Celsius. The value, -273.15 degrees Celsius, is called "absolute zero." At this temperature it is thought that molecular motion stops. Since it cannot get any colder than –273.15 °C, the Kelvin scale uses this number as zero. Its unit, the degree Kelvin, is equal to the degree Celsius.
Conversion Equations:
- To convert Fahrenheit to Celsius use:
Celsius = (Fahrenheit – 32) * 5/9
- To convert Celsius to Fahrenheit use:
Fahrenheit = (Celsius * 9/5) +32
- To convert Celsius to Kelvin use:
Kelvin = Celsius + 273
Time Units:
bp: (years) before present
kbp: thousands of years before present
mbp: millions of years before present
Concentration Units:
For very small concentrations of gases, atmospheric scientists use the following units:
ppmv: parts per million (106) by volume; the fraction of volume of gas occupied by a component multiplied by 1,000,000. If there is 3 ppm of CO2 in a bottle filled with gas, then for every 1,000,000 molecules in the bottle, 3 of those molecules are CO2.
ppbv: parts per billion (109) by volume; the fraction of volume of gas occupied by a component multiplied by 1,000,000,000. If there is 3 ppb of CO2 in a bottle filled with gas, then for every 1,000,000,000 molecules in the bottle, 3 molecules of those are CO2.
pptv: parts per trillion (1012) by volume; the fraction of volume of gas occupied by a component multiplied by 1,000,000,000,000. If there is 3 ppt of CO2 in a bottle filled with gas, then for every 1,000,000,000,000 molecules in the bottle, 3 of those molecules are CO2.
Mass Units:
When dealing with the enormous quantities of carbon discussed in global climate change studies, scientists use the following units:
tonne: a unit of weight equal to 1000 kg (103 kg).
kt: kilotonnes; equal to 1000 tonnes or 106 kg.
GtC: gigatonnes of carbon; 1 GtC is equal to 109 tonnes of carbon or 1012 kg. 3.7 Gt carbon dioxide will give 1 GtC. To give you an idea how big this unit is: in 1997 the total supply of petroleum for the USA (including imports) was approximately 1 Gt per year.
TgC: teragrams of carbon or 1012 grams of carbon.
PgC: petagrams of carbon or 1015 grams of carbon; 1 PgC is equal to 1 Gigatonne of carbon.
Scientific Notation:
Fraction |
Prefix
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Symbol
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Multiple
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Prefix
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Symbol
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10-1
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deci
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d
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10
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decca
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da
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10-2
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cent
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c
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102
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hecto
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h
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10-3
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milli
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m
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103
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kilo
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k
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10-6
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micro
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106
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mega
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M
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10-9
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nano
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n
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109
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giga
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G
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10-12
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pico
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p
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1012
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tera
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T
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10-15
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femto
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f
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1015
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peta
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P
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10-18
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atto
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a
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Some Chemical Symbols:
O2: molecular oxygen
O3: ozone
N2: molecular nitrogen
N2O: nitrous oxide
NO: nitric oxide
NO3: nitrate radical
NOx: Sum of NO and NO2
NO3- : nitrate ion
HNO3: nitric acid
NH3: ammonia
NH4+ : ammonium ion
H2: molecular hydrogen
H2O: water
OH: hydroxyl
HO2: hydroperoxyl
HOx: the sum OH and HO2
C: carbon; there are 3 isotopes: 12C, 13C, 14C
CO: carbon monoxide
CO2: carbon dioxide
F2: molecular fluorine
Cl2: molecular chlorine
Br2: molecular bromine
CFC: chlorofluorocarbon
CFC-11: CFCl3 or trichlorofluoromethane
CFC-12: CF2Cl2 or dichlorodifluoromethane
CFC-113: C2F3Cl2 or trichlorotrifluoroethane
CFC-114: C2F4Cl2 or dichlorotetrafluoroethane
CFC-115: C2F5Cl or chloropentafluoroethane
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