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# Student_01_1 - ACTIVITY 01-1 Units of Measurement WHY?...

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1 W HY ? Units identify the scale that is used in making a measurement and are essential for the measurement to be meaningful. For example, if someone tells you that a person is 60 tall, you do not know whether they are referring to a child or possibly an adult until you know the units. The units could be inches or centimeters, but probably are not feet or meters. In your study of chemistry and its applications, you need to be familiar with the basic units that are used for mass, length, time, temperature, electrical current, and amount of substance. Pre f xes to the units make it quicker and easier to write very large or very small numbers, e.g., 5,600,000 g = 5.6 Mg or 0.000001 s = 1 μ s. Other units are derived from these basic units. For example, units of volume are derived from units of length, and units of energy are derived from units of mass, length, and time. You also need to be able to convert from one set of units to another because different countries, disciplines, and even sub-disciplines of chemistry often use different units for the same quantity. For example, in the United States speed limits are given as miles per hour; in many other countries speed limits are given as kilometers per hour. L EARNING O BJECTIVES Identify the units used to measure physical quantities Become familiar with the pre f xes used for larger and smaller quantities Master the use of unit conversion in solving problems S UCCESS C RITERIA Associate units with physical quantities • Replace pre f xes by multiplying by appropriate numerical factors Identify, set up, compute, and validate unit conversions P REREQUISITE • Exponential notation M ODEL 1: I NTERNATIONAL S YSTEM OF U NITS (SI U NITS ) Table 1 Physical Quantity Name of Unit Abbreviation mass kilogram kg length meter m time

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## This note was uploaded on 09/19/2011 for the course CHE 1112R taught by Professor Meghee during the Fall '11 term at St. Johns Duplicate.

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Student_01_1 - ACTIVITY 01-1 Units of Measurement WHY?...

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