2.6 SI Units2.6 SI Units

The International System of Units, SI, is The International System of Units, SI, is a revised version of the metric systema revised version of the metric system

Correct units along with numerical Correct units along with numerical values are critical when communicating values are critical when communicating measurements.measurements.

The are seven base SI units (Table 2.1) The are seven base SI units (Table 2.1) of which other SI units are derived.of which other SI units are derived. Sometimes non-SI units are preffered for Sometimes non-SI units are preffered for

convience or practical reasonsconvience or practical reasons

2.6 SI Units – Table 2.22.6 SI Units – Table 2.2QuantityQuantity SI Base or Derived SI Base or Derived

UnitUnitNon-SI UnitNon-SI Unit

LengthLength meter (m)meter (m)

VolumeVolume cubic meter (mcubic meter (m33)) literliter

MassMass kilogram (kg)kilogram (kg)

DensityDensity grams per cubic grams per cubic centimeter (g/cm3); centimeter (g/cm3); grams per mililiter grams per mililiter (g/mL)(g/mL)

TemperatTemperatureure

kelvin (K)kelvin (K) degree Celcius (°C) degree Celcius (°C)

TimeTime second (s)second (s)

PressurePressure Pascal (Pa)Pascal (Pa) atmosphere (atm); atmosphere (atm); milimeter of mercury milimeter of mercury (mm Hg)(mm Hg)

EnergyEnergy joule (J)joule (J) calorie (cal)calorie (cal)

Common SI Prefixes Common SI Prefixes

Units larger than the base unitUnits larger than the base unit

TeraTera TT ee1212 base base unitsunits

termeter (Tm)termeter (Tm)

GigaGiga GG ee9 9 base base unitsunits

gigameter gigameter (GM)(GM)

MegaMega MM ee6 6 base base unitsunits

megameter megameter (Mm)(Mm)

KiloKilo kk ee3 3 base base unitsunits

kilometer kilometer (km)(km)

HectoHecto hh ee2 2 base base unitsunits

hectometer hectometer (hm)(hm)

DekaDeka dada ee1 1 base base unitsunits

decameter decameter (dam)(dam)

Base Base UnitUnit

ee0 0 base base unitsunits

meter (m)meter (m)

Common SI PrefixesCommon SI Prefixes

Units smaller than the base unit Units smaller than the base unit

Base Base UnitUnit

ee0 0 base base unitsunits

meter (m)meter (m)

DeciDeci dd ee-1 -1 base base unitsunits

decimeter decimeter (dm)(dm)

CentiCenti cc ee-2 -2 base base unitsunits

centimeter centimeter (cm)(cm)

MilliMilli mm ee-3 -3 base base unitsunits

millimeter millimeter (mm)(mm)

MicroMicro μμ ee-6 -6 base base unitsunits

micrometer micrometer ((μμm)m)

NanoNano nn ee-9 -9 base base unitsunits

Nanometer Nanometer (nm)(nm)

PicoPico pp ee-12 -12 base base unitsunits

picometer picometer (pm)(pm)

Common SI PrefixesCommon SI Prefixes

A mnemonic device can be used to A mnemonic device can be used to memorize these common prefixes in memorize these common prefixes in the correct order:the correct order: TThe he GGreat reat MMonarch onarch KKing ing HHenry enry DDied ied

BBy y DDrinking rinking CChocolate hocolate MMocha ocha MMilk ilk NNot ot PPilsnerilsner

2.7 Units of Length2.7 Units of Length

The basic unit of length is the The basic unit of length is the metermeter Prefixes can be used with the base Prefixes can be used with the base

unit to more easily represent small unit to more easily represent small or large measurementsor large measurements Example: A hyphen (12 point font) Example: A hyphen (12 point font)

measures about 0.001 m or 1 mm.measures about 0.001 m or 1 mm. Example: A marathon race is Example: A marathon race is

approximately approximately

42,000 m or 42 km.42,000 m or 42 km.

2.7 Concept Practice2.7 Concept Practice

15. Use the tables in the text to order 15. Use the tables in the text to order these lengths from smallest to these lengths from smallest to largest.largest.

a. centimetera. centimeter

b. micrometerb. micrometer

c. kilometerc. kilometer

d. millimeterd. millimeter

e. metere. meter

f. decimeterf. decimeter

- 1 (smallest)- 1 (smallest)

- 2- 2

- 3- 3

- 4- 4- 5- 5

- 6 (largest)- 6 (largest)

2.8 Units of Volume2.8 Units of Volume

The space occupied by any sample of The space occupied by any sample of matter is called its matter is called its volumevolume The volume ofThe volume of rectangular solids rectangular solids can can

be calculated by multiplying the be calculated by multiplying the lengthlength by by widthwidth by by heightheight Units are cubed because you are measuring Units are cubed because you are measuring

in 3 dimensionsin 3 dimensions Volume ofVolume of liquids liquids can be measured can be measured

with a with a graduated cylindergraduated cylinder, a , a pipetpipet, a , a buretburet, or a , or a volumetric flaskvolumetric flask

2.8 Units of Volume2.8 Units of Volume

A convenient unit of measurement for A convenient unit of measurement for volume in everyday use is the liter (L)volume in everyday use is the liter (L)

Milliliters (mL) are commonly used for Milliliters (mL) are commonly used for smaller volume measurements and smaller volume measurements and liters (L) for larger measurementsliters (L) for larger measurements 1 mL = 1 cm1 mL = 1 cm33

10 cm x 10 cm x 10 cm = 1000 cm10 cm x 10 cm x 10 cm = 1000 cm33 = 1 L = 1 L

2.8 Units of Volume2.8 Units of Volume

2.8 Concept Practice2.8 Concept Practice

17. From what unit is a measure of 17. From what unit is a measure of volume derived?volume derived?

A: Volume is a length measurement A: Volume is a length measurement cubed.cubed.

2.8 Practice2.8 Practice

18. What is the volume of a paperback 18. What is the volume of a paperback book 21 cm tall, 12 cm wide, and 3.5 book 21 cm tall, 12 cm wide, and 3.5 cm thick?cm thick?

A: 882 cmA: 882 cm33 → → 880 cm880 cm33; ; 8.8 x 108.8 x 102 2 cmcm33

19. What is the volume of a glass 19. What is the volume of a glass cylinder with an inside diameter of 6.0 cylinder with an inside diameter of 6.0 cm and a hiegth of 28 cm?cm and a hiegth of 28 cm?

V=V=ππrr22hh

A: A: 790 cm790 cm33; ; 7.9 x 107.9 x 102 2 cmcm33

2.9 Units of Mass2.9 Units of Mass A person on the moon would weigh 1/6 of A person on the moon would weigh 1/6 of

his/her weight on Earth.his/her weight on Earth. This is because the force of gravity on the This is because the force of gravity on the

moon is approximately 1/6 of its force of moon is approximately 1/6 of its force of Earth.Earth.

Weight is a forceWeight is a force – it is a measure of the pull – it is a measure of the pull on a given mass by gravity; it can change by on a given mass by gravity; it can change by location.location.

Mass is the quantity of matter an Mass is the quantity of matter an object containsobject contains Mass remains constant regardless of location.Mass remains constant regardless of location.

2.9 Units of Mass2.9 Units of Mass

The The kilogramkilogram is the basic SI unit of is the basic SI unit of massmass It is defined as the mass of 1 L of water It is defined as the mass of 1 L of water

at 4°C.at 4°C. A gram, which is a more commonly A gram, which is a more commonly

used unit of mass, is 1/1000 of a used unit of mass, is 1/1000 of a kilogramkilogram 1 gram = the mass of 1 cm1 gram = the mass of 1 cm33 of water at of water at

4°C.4°C.

2.9 Concept Practice2.9 Concept Practice20. As you climbed a mountain and the force 20. As you climbed a mountain and the force

of gravity decreased, would your weight of gravity decreased, would your weight increase, decrease, or remain constant? increase, decrease, or remain constant? How would your mass change? Explain.How would your mass change? Explain.

A: Your weight would decrease; mass would A: Your weight would decrease; mass would remain constant.remain constant.

21. How many grams are in each of these 21. How many grams are in each of these quantities?quantities?

a. 1 cga. 1 cg b. 1 b. 1 μμgg c. 1 kgc. 1 kg d. 1mgd. 1mg

A: 0.01g 0.000001g 1000g 0.001 gA: 0.01g 0.000001g 1000g 0.001 g