Kilogram, SI unit

There are a few basic numerical and experimental tools with which you must be familiar. Fundamental measurements in analytical chemistry, such as mass and volume, use base SI units, such as the kilogram (kg) and the liter (L). Other units, such as power, are defined in terms of these base units. When reporting measurements, we must be careful to include only those digits that are significant and to maintain the uncertainty implied by these significant figures when transforming measurements into results. 

The viscosity ratio or relative viscosity, Tj p is the ratio of the viscosity of the polymer solution to the viscosity of the pure solvent. In capillary viscometer measurements, the relative viscosity (dimensionless) is the ratio of the flow time for the solution t to the flow time for the solvent /q (Table 2). The specific (sp) viscosity (dimensionless) is also defined in Table 2, as is the viscosity number or reduced (red) viscosity, which has the units of cubic meters per kilogram (m /kg) or deciUters per gram (dL/g). The logarithmic viscosity number or inherent (inh) viscosity likewise has the units m /kg or dL/g. For Tj g and Tj p, the concentration of polymer, is expressed in convenient units, traditionally g/100 cm but kg/m in SI units. The viscosity number and logarithmic viscosity number vary with concentration, but each can be extrapolated (Fig. 9) to zero concentration to give the limiting viscosity number (intrinsic viscosity) (Table 2). 

The gray is also used for the ionising radiation quantities, specific energy imparted, kerma, and absorbed dose index, which have the SI unit joule per kilogram. 

The actual yield may be obtained from algebraic calculations or trial-and-error calculations when the heat effects in the process and any resultant evaporation are used to correc t the initial assumptions on calculated yield. When calculations are made by hand, it is generally preferable to use the trial-and-error system, since it permits easy adjustments for relatively small deviations found in practice, such as the addition of wash water, or instrument and purge water additions. The following calculations are typical of an evaporative ciy/staUizer precipitating a hydrated salt, if SI units are desired, kilograms = pounds X 0.454 K = (°F 459.7)/I.8. 

It is usual these days to express all physical quantities in the system of units referred to as the Systeme International, SI for short. The International Unions of Pure and Applied Physics, and of Pure and Applied Chemistry both recommend SI units. The units are based on the metre, kilogram, second and the ampere as the fundamental units of length, mass, time and electric current. (There are three other fundamental units in SI, the kelvin, mole and candela which are the units of thermodynamic temperature, amount of substance and luminous intensity, respectively.)... 

Jeffryes, Alec, 628 Joliot, Frederic, 517 Joliot-Curie, Irfcne, 248 Joule The base SI unit of energy, equal to the kinetic energy of a two-kilogram mass moving at a speed of one meter per second, 135,635 Joule, James, 199... 

In this book, we will express our thermodynamic quantities in SI units as much as possible. Thus, length will be expressed in meters (m), mass in kilograms (kg), time in seconds (s), temperature in Kelvins (K), electric current in amperes (A), amount in moles (mol), and luminous intensity in candella (cd). Related units are cubic meters (m3) for volume, Pascals (Pa) for pressure. Joules (J) for energy, and Newtons (N) for force. The gas constant R in SI units has the value of 8.314510 J K l - mol-1, and this is the value we will use almost exclusively in our calculations. 

Kelvin scale A fundamental scale of temperature on which the triple point of water lies at 273.16 K and the lowest attainable temperature is at 0. The unit on the Kelvin scale is the kelvin, K. ketone An organic compound containing a carbonyl group between two carbon atoms, having the form R—CO R. Example CH3—CO—CH2CH , butanone. kilogram (kg) The SI unit of mass. See also Appendix IB. 

The SI units for kinetic energy are kilogram-meters /second. Because energy is so fundamental, this combination of units has its own name and symbol, the joule (J) IJ = 1 kg... 

SI Units—The International System of Units as defined by the General Conference of Weights and Measures in 1960. These units are generally based on the meter/kilogram/second units, with special quantities for radiation including the becquerel, gray, and sievert. 

The ICRU (1980), ICRP (1984), and NCRP (1985) now recommend that the rad, roentgen, curie, and rem be replaced by the SI units gray (Gy), Coulomb per kilogram (C/kg), Becquerel (Bq), and sievert (Sv), respectively. The relationship between the customary units and the international system of units (SI) for radiological quantities is shown in Table D-5. 

For historic reasons a number of different units of measurement have evolved to express quantity of the same thing. In the 1960s, many international scientific bodies recommended the standardisation of names and symbols and the adoption universally of a coherent set of units—the SI units (Systeme Internationale d Unites)— based on the definition of five basic units metre (m) kilogram (kg) second (s) ampere (A) mole (mol) and candela (cd). 

The units we use in daily life, such as kilogram (or pound) and meter (or inch) are tailored to the human scale. In the world of quantum mechanics, however, these units would lead to inconvenient numbers. For example, the mass of the electron is 9.1095 X J0 31 kg and the radius of the first circular orbit of the hydrogen atom in Bohr s theory, the Bohr radius, is 5.2918 X 10 11 m. Atomic units, usually abbreviated as au, are introduced to eliminate the need to work with these awkward numbers, which result from the arbitrary units of our macroscopic world. The atomic unit of length is equal to the length of the Bohr radius, that is, 5.2918 X 10 n m, and is called the bohr. Thus 1 bohr = 5.2918 X 10"11 m. The atomic unit of mass is the rest mass of the electron, and the atomic unit of charge is the charge of an electron. Atomic units for these and some other quantities and their values in SI units are summarized in the accompanying table. 

The prefixes should be attached directly to the SI base unit e.g., kilogram, millisecond, gigameter, etc. Similarly, the abbreviations attach directly to the abbreviation for the SI units e.g., cm, Mg, mK, etc. Do not use two or more of the SI units. Although kilogram is the normal base unit for mass, the prefixes are added to gram (g), not kilogram (kg). 

The problem with the SI base unit being a kilogram is the kilo part. The philosophical idea behind the SI system says any parameter (physical, chemical, mechanical, etc.) can be derived from a suitable combination of the others. For example, the SI unit of velocity is metres per second (m s-1), which is made up of the two SI fundamental units of length (the metre) and time (the second). A few of these combinations are cited in Table 1.3. 

Contacting power is variously expressed in units of MJ/1000 m3 (SI), kWh/1000 m3 (meter-kilogram-second system), and hp/(1000 ft3/min) (U.S. customary). Relationships for conversion to SI units are... 

According to lUPAC, although the SI unit of amount of substance is the mole, the physical quantity amount of substance should no longer be called number of moles", just as the physical quantity mass should not be called number of kilograms ("Quantities, Units and Symbols in Physical Chemistry", lUPAC, p. 4, Blackwell Scientific Publications, Oxford, 1988). 

In the present book, for magnetism we use the SI unit that is based on the MKS A (meter, kilogram, second, ampere) system. In accordance with that, the tesla (1T = 10" gauss) was presented as the magnetic unit in Chapter 17 (see Fig. 17.10a and b). It is useful to know both the SI and Gaussian systems and be able to convert between them. Thus, when one attempts to solve a magnetics problem, to avoid errors one is well advised to stick to a single convenient unit system. A useful conversion table of... 

The quantity of absorbed energy absorbed per unit mass of a substance, object, or organism in an irradiated medium. Symbolized by D, the SI unit is the gray (Gy joules per kilogram). The unit rad is also commonly used (1 rad = 0.01 Gy). 2. The amount of substance (e.g., pharmaceutical) absorbed by an organism or cell. 

The International System of Units (SI) built on seven base units the unit of mass is the kilogram, the unit of time is the second, the unit of length is the meter, the unit of electric current is the ampere, the unit of tempera-... 

The SI unit of power or radiant flux (symbolized by W) equal to one joule per second (or, meter per kilogram per second ). With respect to electric currents, the watt is the rate of work expressed by a current of one ampere and a potential difference of one volt. See Power Radiant Flux... 

Gray SI unit to measure the amount of radiation dose equal to deposition of one joule of energy into one kilogram of matter Greenhouse Effect warming of the Earth due to absorption of infrared radiation by particular atmospheric gases such as H O, CO, and CH ... 

In the SI system, mass is measured in kilograms. The standard SI units for mass and length were chosen by the Scientific Powers That Be because many objects that you encounter in everyday life have masses between 1 and 100 kllogrcims and have dimensions on the order of 1 meter. Chemists, however, are most often concerned with very... 

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