Prefixes scientific

Chemists frequently work with measurements that are very large or very small. A mole, for example, contains 602,213,670,000,000,000,000,000 particles, and some analytical techniques can detect as little as 0.000000000000001 g of a compound. For simplicity, we express these measurements using scientific notation thus, a mole contains 6.0221367 X 10 particles, and the stated mass is 1 X 10 g. Sometimes it is preferable to express measurements without the exponential term, replacing it with a prefix. A mass of 1 X 10 g is the same as 1 femtogram. Table 2.3 lists other common prefixes. 

Scientific measurements are expressed in the metric system. As you know, this is a decimal-based system in which all of the units of a particular quantity are related to one another by factors of 10. The more common prefixes used to express these factors are listed in Table 1.2 (page 7). 

Table 1-2 Frequently Used Scientific Prefixes for Magnitudes...

Using the same logic, the chemical compound H20 can also be named using the prefixes mono- and di-. Because there is only one oxygen atom in water and the oxygen is the second element in the compound, the prefix mono- is used. The scientific name for H20 is dihydrogen monoxide. Of course, this compound is also much better known by its common name—water. 

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. 

Chemists routinely measure quantities that run the gamut from very small (the size of an atom, for example) to extremely large (such as the number of particles in one mole). Nobody, not even chemists, likes dealing with scientific notation (which we cover in Chapter 1) if they don t have to. For these reasons, chemists often use a metric system prefix (a word part that goes in front of the base unit to indicate a numerical value) in lieu of scientific notation. For example, the size of the nucleus of an atom is roughly 1 nanometer across, which is a nicer way of saying 1x10- meters across. The most useful of these prefixes are in Table 2-2. 

Your lab partner has measured the mass of your sample to be 2,500 g. How can you record this more nicely (without scientific notation) in your lab notebook using a metric system prefix ... 

Scientific measurements range from fantastically large to incredibly small numbers, and units that are appropriate for one measurement may be entirely inappropriate for another. To avoid the creation of many different sets of units, it is common practice to vary the size of a fundamental unit by attaching a suitable prefix to it. Table 4-1 shows common metric prefixes and the multiples they indicate for any given unit of measurement. Thus a l g gs ater is 1000 meters, a microgram is 10-6 ram ana a nanosecond is Q-9... 

As we have seen in some of the examples described above, an added complication in performing chemical calculations often involves the presence of units. More often than not, these numbers may be expressed in scientific form, and so, in order to rationalize and simplify their specification, it is conventional to use the names and abbreviations given in Table l. 2, adjusting the decimal number given as prefix as appropriate. 

The situation for numbers ending in zeros that are not to the right of the decimal point can be unclear, so this situation should be avoided by using scientific notation or a different decimal prefix. 

The metric system is a decimal system, based on powers of 10. Table 2.5 is a list of the prefixes for the various powers of 10. Between scientific notation and the prefixes shown below, it is very simple to identify, name, read, and understand 36 decades of power of any given base or derived unit. 

For very large numbers with units of measure, use scientific notation or choose an appropriate multiplying prefix for the unit to avoid numbers of more than four digits. 

Scientific measurements are based on mass (not weight), and the Syst4me International (SI) unit is the gram (g). For further details on SI units and common prefixes please see Appendix 1. 

To use exponential notation to work with very large and very small numbers To use the basic elements of the metric system—a system of units and prefixes designed to make scientific calculations as easy as possible... 

The problem of changing over a highly industrialized nation such as the United States to a new system of measurements is a substantial one. Once the metric system is in general use in the United States, its simplicity and convenience will be enjoyed, but the transition period, when both systems are in use, can be difficult. Nevertheless, it will be easier than it seems. While the complete SI is intimidating because it covers every conceivable kind of scientific measurement over an enormous range of magnitudes, there are only a small number of units and prefixes that are used in everyday life. 

Time The SI base unit for time is the second (s). The frequency of microwave radiation given off by a cesium-133 atom is the physical standard used to establish the length of a second. Cesium clocks are more reliable than the clocks and stopwatches that you use to measure time. For ordinary tasks, a second is a short amount of time. Many chemical reactions take place in less than a second. To better describe the range of possible measurements, scientists add prefixes to the base units. This task is made easier because the metric system is a decimal system. The prefixes in Table 2-2 are based on multiples, or factors, of ten. These prefixes can be used with all SI units. In Section 2.2, you will learn to express quantities such as 0.000 000 015 s in scientific notation, which also is based on multiples of ten. 

Prefix Symbol Factor Scientific notation Example... 

Rewrite the following in scientific notation, using only the base units of Table B.l, without prefixes. 

Prefix Symbol Multiply the base by Scientific Notation... 

The definition of the term nanoparticles varies significantly depending on the scientific community where it is used. While in material sciences, the prefix nano is generally restricted to structures smaller than 10 nm or, at the most, 100 nm, the same term in pharmaceutical sciences may refer to particles with up to 1000 nm in diameter. However, when dealing with nanoparticles, there is general agreement on the phase state of the particles themselves which are supposed to be solid and dispersed in a continuous solid or fluid medium. In the following, we stick to a nomenclature that is common in pharmaceutical applications and has been proposed by Kreuter spherical nanoparticles with a compact solid structure are referred to as nanospheres, while hollow nanoparticles with a fluid content are named nanocapsules. 

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