l>Lesson I: The Metric System and SI Units  A meter is 3.37 inches much more than a yard.

You are watching: Why do scientists use the metric system A liter is 1.82 liquid ounces an ext than a quart. A dime weighs about one gram.
IntroductionThe metric device is the wanted system of scientific units for number of reasons:The bulk of countries in the world employ the metric device of measurement.The prefixes attached come metric units bring the same an interpretation for all base units.The metric device is based upon strength of ten, i beg your pardon is practically because:A measurement in the metric mechanism that is stood for by a reasonable number stays a rational numberafter metric unit conversion. (For example, 250 mm = 25 centimeter = .25 m). In comparison irrational unit systems, such as the English system, carry out not have the same residential or commercial property (For example, 250 customs = 20.8333... Ft = 0.0039457... Mile)Because metric units are decimal-based, castle are quickly converted by relocating the decimal point.The terms mass and also weight are frequently used interchangebly in chemistry. Strictly speaking, weight is the force (F) linked with a offered mass (m) as it is increased (a) through gravity: F = m × aThe English mechanism unit of mass is the slug, which as soon as multiplied by the acceleration of gravity (32 ft/sec2) gives the weight in pounds.Length
 Metric base UnitsThe metric mechanism uses the adhering to base units:Unit of MeasurementNameAbbreviation Meter m Mass Gram g Volume Liter L
Frequently the above units room too small or more often too big to accordingly scale the measure up quantity. That is then vital to subdivide or expand our measure up unit. This will be disputed in the section on prefixes.

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 The liter is no the SI unit that volume Volume is a unit derived from length. The volume (V) the a cube that has length (l) = 1.0 cm, broad (w) = 1.0 cm, and height (h) is given by:V = together × w × h = 1.0 cm × 1.0 cm × 1.0 cm= 1.0 cm3By definition, 1.0 cm3 = 1.0 mL  It adheres to from dimensional analysis that 1.0 dm3 = 1.0 L.SI Units
The metric-based Système worldwide or SI systems are used to standardize the report or calculation of clinical quantities:Physical QuantityName the UnitAbbreviationLength
Meterm
MassKilogramkg
TemperatureKelvinK
TimeSeconds
Amount that SubstanceMolemolElectric CurrentAmpereILuminous IntensityLumenIv
The SI units are offered to construct all various other units (these are called derived units
). Some examples:PropertySymbolDimensionsName
Velocityvm · s-1
AreaAm2
Frequencyvs-1Hertz (Hz)
ForceFkg · m · s-2Newton (N)
EnergyEkg · m2 · s-2Joule (J)
Exa- Outside the united States, words "meter" is assignment "metre" and also the indigenous "liter" is spelled "litre." Metric PrefixesTo readjust the range of the base units, prefixes are attached. A prefix represents a factor whereby the base unit should be multiplied. Metric prefixes are detailed below (The prefixes most-commonly used in chemistry are listed in red):PrefixSymbolDecimalValuePower that Ten E 1,000,000,000,000,000,000 1018 Peta- P 1,000,000,000,000,000 1015 Tera- T 1,000,000,000,000 1012 Giga- G 1,000,000,000 109 Mega- M 1,000,000 106 Kilo- k 1,000 103 Hecto- h 100 102 Deka- da 10 101 (no prefix) 1 100 Deci- d 0 .1 10-1 Centi- c 0 .01 10-2 Milli- m 0 .001 10-3 Micro- µ 0 .000001 10-6 Nano- n 0 .000000001 10-9 Pico- p 0 .000000000001 10-12 Femto- f 0 .000000000000001 10-15 Atto- a 0 .000000000000000001 10-18
 In addition to the basic metric units, plenty of other scientific quantities additionally employ this device of prefixes: 1 Mb = 1 Megabyte = 1 × 106 byte 1 Food Calorie = 1 kcal= 1 kilocalorie = 1 × 103 calorie 1 ns = 1 nanosecond = 1 × 10-9 second 1 pf = 1 picofarad = 1 × 10-12 farad 1 kWH = 1 kiloWatt·hour = 1 × 103 Watt·hour
The metric prefixes can be work to range the base units so the they deserve to represent anything native a very big numeric worth (for instance by making use of prefixes such as Exa, Tera, or Mega) to a very little numeric value (for exampleby using prefixes such together Atto, Femto, or Pico). Scaling the unit increase or down when reporting measurements is an excellent practice because:It can be supplied to keep the numeric value of dimensions to reasonably-sized numbers, say between values of 0.01 come 100.It can be used to remove ambiguous place-holding zeroes in measurments, so that the number of far-ranging figures are appropriately represented.The prefixes instantly convey how many decimal location moves are forced of the numeric value. Because that example, using the clinical notation worth of the metric prefixes):1 centimeter = 1 centimeter = 1 × 10-2 meter = 0.01 meter1 kg = 1 kilogram = 1 × 103 gram = 1000 gram1 µL= 1 microliter = 1 × 10-6 liter = 0.000001 literFor further explanation that unit interconversion using the metric prefixes as conversion factors, visit the dimensional analysis page. In enhancement to the typical metric prefixes, the Ångstrom is likewise a frequently used unit the arises in measurements on the atom scale:1 Ångstrom = 1 Å = 1 × 10-10 meter
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