Metric system conversion factors

P. Anderton and P. H. Bigg, Changing to the Metric System - Conversion Factors, Symbols and Definitions , 3rd edn.. Her Majesty s Stationery Office, London, 1969. The Use of SI Units , British Standards Institution, PD5686, 1969. 

Units. The SI system of units and conversion factors (qv) has been formally adopted worldwide, with the exception of Bmnei, Burma, Yemen, and the United States. The participation of the United States in the metrication movement is evident by the passage of the Metric Acts of 1866 and 1975 and the subsequent estabUshment of the American National Metric Council (private) and the U.S. Metric Board (pubHc) to plan, coordinate, monitor, and encourage the conversion process. 

Conversion of units from one system to another is simply carried out if the quantities are expressed in terms of the fundamental units of mass, length, time, temperature. Typical conversion factors for the British and metric systems are ... 

Beginning students often regard the metric system as difficult because it is new to them and because they think they must learn all the English-metric conversion factors (Table 2-3). Engineers do have to work in both systems in the United States, but scientists generally do not work in the English system at all. Once you familiarize yourself with the metric system, it is much easier to work with than the English system is. 

Still other units encountered in the literature and workplace come from various other systems (absolute and otherwise). These include metric systems (c.g.s. and MKS), some of whose units overlap with SI units, and those (FPS) based on English units. The Fahrenheit and Rankine temperature scales correspond to the Celsius and Kelvin, respectively. We do not use these other units, but some conversion factors are given in Appendix A. Regardless of the units specified initially, our approach is to convert the input to SI units where necessary, to do the calculations in SI units, and to convert the output to whatever units are desired. 

Chemistry is full of calculations. Our basic goal is to help you develop the knowledge and strategies you need to solve these problems. In this chapter, you will review the Metric system and basic problem solving techniques, such as the Unit Conversion Method. Your textbook or instructor may call this problem solving method by a different name, such as the Factor-Label Method and Dimensional Analysis. Check with your instructor or textbook as to for which SI (Metric) prefixes and SI-English relationships will you be responsible. Finally, be familiar with the operation of your calculator. (A scientific calculator will be the best for chemistry purposes.) Be sure that you can correctly enter a number in scientific notation. It would also help if you set your calculator to display in scientific notation. Refer to your calculator s manual for information about your specific brand and model. Chemistry is not a spectator sport, so you will need to Practice, Practice, Practice. 

Conversion factors for the U.S. Customary System, metric system, and International System ... 

Table 4-2 shows how some of the basic metric units are related to units commonly used in English-speaking countries for nonscientitle measurements. Although the United States, Great Britain, and Canada have officially resolved to convert to the metric system, it will be many years before the conversion is complete. In the meantime, you must learn to convert from one system to the other. The three conversion factors given in Table 4-2 (rounded off to 2.54... 

The international system of units is described in detail in NIST Special Publication 81l,1 and lists of physical constants and conversions factors of selected unit conversions1 5 are given in the following tables. The conversions are presented in matrix format when all of the units are of a convenient order of magnitude. When some of the unit conversions are of tittle value (such as the conversion between metric tons and grains), tabular form is followed, with the less useful units omitted. 

Convert 3.50 yards to (a) millimeters, (b) meters. According to Table 1-2, the conversion factor used to move between the English and metric system (SI) units is 1 in/2.54cm (2.54 x 10-2 m). 

The metric system of weights and measures is used by scientists of all fields, including chemists. This system uses the base 10 for measurements for conversions, measurements may be multiplied or divided by 10. Table 2.1 lists the most frequently used factors in the laboratory which are based on powers of 10. 

Volume in the metric system is expressed in liters (L) and milliliters (mL). Another way of expressing milliliters is in cubic centimeters (cm3 or cc). Several conversion factors for volume measurements are listed below. 

Mass measurements of objects are carried out with the laboratory balance. Many types of balances are available for laboratory use. The proper choice of a balance depends upon what degree of accuracy is needed for a measurement. The standard units of mass are the kilogram (kg) in the SI system and the gram (g) in the metric system. Some conversion factors are listed below. 

In the literature, information is found using different systems of units metric, SI, and the English system. Quotations from the literature are presented in their original form. It would be difficult to change all these units in the book to one system. To assist the reader in converting these units, an appendix is provided with conversion factors for all units found in the text. 

The metric system problem, part (a), can be solved without paper and pencil— by moving the decimal point in 5.200 three places to the right. The English system conversion, part (b), requires that we remember the number of yards per mile (harder than the 1000 m/km metric conversion factor) and that we use pencil and paper or a calculator to do the arithmetic. The conversion factor 1000 is used for kilograms, kilohters, kilowatts, and any other factor involving the prefix kilo-. The English conversion factor 1760 yd/mile is not used in any other conversion. 

The base units of the American engineering system are the foot (ft) for length, the pound-mass (Ibm) for mass, and the second (s) for time. This system has two principal difficulties. The first is the occurrence of conversion factors (such as 1 ft/12 in), which, unlike those in the metric systems, ate not multiples of 10 the second, which has to do with the unit of force, is discussed in the next section. 

With the current trend toward metrication, the question of using a consistent system of units has been a problem. Wherever possible, the authors of this Handbook of Environmental Engineering series have used the British system (fps) along with the metric equivalent (mks, cgs, or SIU) or vice versa. For the convenience of the readers around the world, this book provides a 55-page detailed Conversion Factors for Environmental Engineers. In addition, the basic and supplementary units, the derived units and quantities, important physical constants, the properties of water, and the Periodic Table of the Elements, are also presented in this document. 

The metric system uses grams to measure weight and liters to measure volume, as shown in Table 7.1. Prefixes are used to indicate the value (Table 7.2). The apothecaries system uses ounces and pounds for weight and teaspoon, and tablespoon to measure volume. Table 7.3 contains conversion factors for the apothecaries system and metric system. 

TABLE 7.3 Conversion Factors for the Apothecaries System and Metric System... 

Patients use the apothecaries system to measure medication when they self-medicate however, the medication may be delivered in metric units. Therefore, the healthcare provider must convert the prescribed dose from metric units to units of the apothecaries system. Use factors in Table 7.3 to convert values. The most common conversions are milliliters to teaspoons, tablespoons, or cups. A cup is measured in ounces. Another common conversion is pounds to kilograms. 

The International Metric System (SI) of units has been used throughout this subsection. Where possible, the estimation equations are set up in dimensionless groups. This makes transparent any conversion factors that should be applied to obtain the property in a desired set of units and eliminates the requirement of specific units for variables. For example, rather than use as a variable with defined units, the dimensionless group P / Pa is used. When a value for P expressed in... 

Conversions between the English and SI (metric) systems are conveniently made by the unit factor method. Several conversion factors are listed in Table 1-7. It may be helpful to remember one each for... 

As you saw in Chapter 1, one of the convenient features of the metric system is that the relationships between metric units can be derived from the metric prefixes. These relationships can easily be translated into conversion factors. For example, milli- means 10 (or 0.001 or 1/1000), so a milliliter (mL) is 10 liters (L). Thus there are 1000 or 10 milliliters in a liter. (A complete list of the prefixes that you need to know to solve the problems in this text is in Table 1.2.) Two possible sets of conversion factors for relating milliliters to liters can be obtained from these relationships. 

Conversion of units within the metric system may be accomplished by using the factor-label method as well. Unit prefixes that dictate the conversion factor facilitate unit conversion (refer to Table 1.1). 

A good rule of thumb to follow is In the metric system the quantity being converted, not the conversion factor, generally determines the number of significant figures. 

It is often necessary to convert a given result from one system of units to another. The best way to do this is by a method called the unit factor method or, more commonly, dimensional analysis. To illustrate the use of this method, we will consider several unit conversions. Some equivalents in the English and metric systems are listed in Table 1.4. A more complete list of conversion factors given to more significant figures appears in Appendix 6. 

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