Units decimal multiples

Prefixes. In SI, 20 prefixes are used and are direcdy attached to form decimal multiples and submultiples of the units (see the introduction to this volume, p. xvi). Prefixes indicate the order of magnitude, thus eliminating nonsignificant digits and providing an alternative to powers of 10 eg, 45 300 kPa becomes 45.3 MPa and 0.0043 m becomes 4.3 mm. 

The Systeme International d Unites (International System of Units) has the abbreviation SI. It includes base units, supplementary and derived units which together form a coherent system of units. Prefixes are used to form decimal multiples and sub-multiples of the SI units. 

See DIN 1305. The previous units pond (p) and kilopond, i.e. kilogram-force, (kp) as well as other decimal multiples of p are no longer used. 

Decimal multiples of the coherent base and derived SI units are formed by attaching to these units the prefixes shown in Table 2. 

When we use a conversion factor, the units are treated just like algebraic quantities they are multiplied or canceled in the normal way. Thus, the units in the denominator of the conversion factor cancel the units in the original data, leaving the units in the numerator of the conversion factor. The same procedure can be used to convert decimal multiples or fractions of units. 

Decimal multiples of SI units are formed by attaching a prefix directly before the unit and a symbol prefix directly before the unit symbol. SI prefixes range from 10 24 to 1024 Only the prefixes you are likely to encounter in chemistry are shown below ... 

Decimal multiples and submultiples of units may be indicated by the use of prefixes as defined in section 3.6 below. 

In the International System there is only one SI unit for each physical quantity. This is either the appropriate SI base unit itself (see table 3.3) or the appropriate SI derived unit (see tables 3.4 and 3.5). However, any of the approved decimal prefixes, called SI prefixes, may be used to construct decimal multiples or submultiples of SI units (see table 3.6). 

To signify decimal multiples and submultiples of SI units the following prefixes may be used [3]. 

The names and symbols of decimal multiples and submultiples of the SI base unit of mass, the kg, which already contains a prefix, are constructed by adding the appropriate prefix to the word gram and symbol g. 

The prefixes listed in Table 16.13 are used to indicate decimal multiples of base and derived SI units. ... 

Decimal multiples and fractions of SI units are designated by prefixes. Those in common use are listed in Table 1.1. Thus we have, for example, that 1 cm = 10" m and 1 kg = 10 g. 

Decimal Multiples and Submultiples of SI Units In practical application of SI units, certain values are too large or too small to be expressed conveniently in the base or derived units. Numerical values can be brought to convenient size when the unit is appropriately modified by official SI prefixes. In general the prefixes are such that the value of the unit changes 1000-fold. However, certain common previously accepted multiples or sub multiples, such as deci- and hecto-, are still accepted in the SI framework. The SI prefixes are listed in Table 1-5 together with their symbols. 

DECIMAL UNIIS. In the SI system a single unit is defined for each quantity, but named decimal multiples and submultiples also are recognized. They are listed in Appendix 1. Time may be expressed in the nondecimal units minutes (min), hours... 

TABLE 1.13 SI Prefixes (Decimal Multiples and Submultiples in SI Are Formed by Adding the Following Prefixes to the SI Unit)... 

Among the base units of the International System, the unit of mass is the only one whose name, for historical reasons, contains a prefix. Names and symbols for decimal multiples and submultiples of the unit of mass are formed by attaching prefix names to the unit name gram and prefix symbols to the unit symbol g ... 

DECIMAL MULTIPLES AND SUBMULTIPLES USED WITH SI UNITS ... 

Table 5 gives the SI prefixes that are used to form decimal multiples and submultiples of SI units. They allow very large or very small numerical values to be avoided. A prefix attaches directly to the name of a unit, and a prefix symbol attaches directly to the symbol for a unit. For example, one kilometer, symbol 1 km, is equal to one thousand meters, symbol 1000 m or 10 m. When prefixes are attached to SI units, the units so formed are called "multiples and submultiples of SI units in order to distinguish them from the coherent system of SI units. 

Table A.4 Prefixes used to construct decimal multiples of units (SI).

The CGPM in 1960 adapted the first series of prefixes and symbols of decimal multiples of SI units. Over the years, the list has been extended to include those listed in Table 6.2. SI is the most common system of units used in the world. 

T SLE 6.2 Ttie List of Decimal Multiples and Prefixes Used with SI Base Units... 

SI units Syst me International d Unit s the international system of units now recommended for all scientific purposes. A coherent and rationalized system of units derived from the m.k.s. units, SI units have now replaced c.g.s. units and Imperial units. The system has seven base units and two dimensionless (formerly called supplementary) units (see Appendix), all other units being derived from these nine units. There are 18 derived units with special names. Each unit has an agreed symbol (a capital letter or an initial capital letter if it is named after a scientist, otherwise the symbol consists of one or two lower-case letters). Decimal multiples of the units are indicated by a set of prefixes whenever possible a prefix representing 10 raised to a power that is a multiple of three should be used. 

Decimal multiples and submultiples to be used with SI units... 

The International System of Units was devised to facilitate communication between scientific and engineering disciplines. Using SI units is highly recommended because it minimizes errors that arise from complicated units conversions. The International System of Units is based on seven base units (Table 2.1). Decimal multiples of these units and derived units are named using the prefixes listed in Table 2.2. 

SI units (SI Systeme fnternational d Unites) The modern coherent rationalized internationally adopted metric system of units. It has seven BASE UNITS and two dimensionless units, formerly called supplementary units. DERIVED UNITS are formed by multiplication and/or division of base units. Standard prefixes are used for decimal multiples and submultiples of SI units, along with standard symbols for both units and prefixes. 

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