CHAPTER 1CHAPTER 1

STANDARDS OF STANDARDS OF MEASUREMENTMEASUREMENT

Section 2Section 2

Units and StandardsUnits and Standards

STANDARD – an exact STANDARD – an exact quantity that people quantity that people agree to use to agree to use to compare compare measurementsmeasurements

Without a standard Without a standard you cannot compare you cannot compare measurementsmeasurements

Measurement SystemsMeasurement Systems

For a measurement to make sense it For a measurement to make sense it must have a NUMBER and a UNITmust have a NUMBER and a UNIT 5meters, 12seconds, 823grams5meters, 12seconds, 823grams Give me 8Give me 8

English System used in the U.S.English System used in the U.S.

Measurement SystemsMeasurement Systems

Metric System Metric System – based on multiples – based on multiples of TENof TEN International System of Units (SI) International System of Units (SI) – –

universally used and understood universally used and understood globally by scientistsglobally by scientists

METRIC SYSTEMMETRIC SYSTEM

BASE UNITS:BASE UNITS:

QUANTITY MEASURED UNIT SYMBOL

Length meter m

Mass kilogram kg

Time second s

Electric current ampere A

Temperature kelvin K

METRIC SYSTEMMETRIC SYSTEM

SI PrefixesSI Prefixes SI is easy to use SI is easy to use

because it’s because it’s based on based on multiples of 10multiples of 10

PREFIXES ARE PREFIXES ARE USED TO USED TO INDICATE WHICH INDICATE WHICH MULTIPLE OF 10MULTIPLE OF 10

METRIC SYSTEMMETRIC SYSTEM

SI PrefixesSI Prefixes

PREFIX SYMBOLMEANING (multiplying

factor)

Kilo- k 1,000

Deci- d 0.1

Centi- c 0.01

Milli- m 0.001

Micro- µ 0.000001

Nano- n 0.000000001

METRIC SYSTEMMETRIC SYSTEM

Converting from one unit to Converting from one unit to anotheranother

Need to use a Need to use a CONVERSION FACTORCONVERSION FACTOR: : a a ratio that is ratio that is equal to ONE equal to ONE and is used to and is used to convert from one unit to anotherconvert from one unit to another

Convert 1gram to milligrams:Convert 1gram to milligrams: 1g x 1g x 1,000mg/1g1,000mg/1g = 1,000mg = 1,000mg

Convert 10meters to kilometersConvert 10meters to kilometers 10m x 10m x 1km/1,000m1km/1,000m = 0.010km = 0.010km

MEASURING DISTANCEMEASURING DISTANCE

LENGTHLENGTH – the distance – the distance between 2 pointsbetween 2 points

METER (m)METER (m) When choosing the unit, When choosing the unit,

make sure it’s appropriate.make sure it’s appropriate.

MEASURING MATTERMEASURING MATTER

MASSMASS – – the quantity of the quantity of mattermatter

KILOGRAM (kg)KILOGRAM (kg) Depends on number Depends on number

and type of atomsand type of atoms

MEASURING TIMEMEASURING TIME

How long it takes How long it takes something to happensomething to happen

SECONDS (s)SECONDS (s) Records HistoryRecords History

MEASURING TEMPERATUREMEASURING TEMPERATURE

How much heat How much heat something hassomething has

KELVIN (K) KELVIN (K) but most often reported but most often reported

scientifically in CELSIUS scientifically in CELSIUS (⁰C)(⁰C)

DERIVED UNITS:DERIVED UNITS:Volume and DensityVolume and Density

VOLUMEVOLUME – amount of space occupied – amount of space occupied by an objectby an object Derived from 3 measurements; Derived from 3 measurements;

V = l × w × h = cmV = l × w × h = cm33

Liters (L)Liters (L) 1 mL = 1 cm1 mL = 1 cm33

DERIVED UNITS:DERIVED UNITS:Volume and DensityVolume and Density

DENSITYDENSITY – mass per unit volume of a – mass per unit volume of a materialmaterial Derived from the mass (g) ÷ volume Derived from the mass (g) ÷ volume

(cm(cm33)) Water is the standard for density 1g/cmWater is the standard for density 1g/cm33

DENSITY OF SOME MATERIALS AT 20⁰C

WATER 1.0 g/cm3

LEAD 11.34 g/cm3

HELIUM 0.0001785 g/cm³