The Metric System

An easy way to measure

SI System

The International System of Units Derived Units Commonly Used in Chemistry Area and Volume: Derived Units Prefixes in the SI System

Measuring

The numbers are only half of a measurement• Measurement = number + unit

It is 10 long 10 what. Numbers without units are meaningless. How many feet in a yard A mile A rod

The Metric System

Easier to use because it is a decimal system Every conversion is by some power of 10. A metric unit has two parts A prefix and a base unit. prefix tells you how many times to divide or

multiply by 10.

Base Units

Length - meter more than a yard - m Mass - grams - a bout a raisin - g Time - second - s Temperature - Kelvin or ºCelsius K or C Energy - Joules- J Volume - Liter - half f a two liter bottle- L Amount of substance - mole - mol

The International System of Units

Length meter m

Mass kilogram kg

Time second s

Amount of substance mole mol

Thermodynamic temperature Kelvin K

Electric current amperes amps

Luminous intensity candela cd

Quantity Name Symbol

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 16

Prefixes

kilo k 1000 times deci d 1/10 centi c 1/100 milli m 1/1000 kilometer - about 0.6 miles centimeter - less than half an inch millimeter - the width of a paper clip wire

Prefixes in the SI System

Power of 10 for Prefix Symbol Meaning Scientific Notation_______________________________________________________________________

mega- M 1,000,000 106

kilo- k 1,000 103

deci- d 0.1 10-1

centi- c 0.01 10-2

milli- m 0.001 10-3

micro- 0.000001 10-6

nano- n 0.000000001 10-9

The Commonly Used Prefixes in the SI System

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 118

The Original Metric Reference

H2O = 1 liter

Volume

1 kg

H2O = 1 kilogram

Mass

1/10 m

1/10 m

1/10 m

Earth = 1 meter

Length

1/10,000,000

The Official Standard Meter

The Official Standard Kilogram

Derived Units Commonly Used in Chemistry

Area square meter m2

Volume cubic meter m3

Force newton N Pressure pascal Pa Energy joule J Power watt W Voltage volt V Frequency hertz Hz Electric charge coulomb C

Quantity Name Symbol

Area and Volume: Derived Units

Area = length x width

= 5.0 m x 3.0 m

= 15 ( m x m)

= 15 m2

Volume = length x width x height

= 5.0 m x 3.0 m x 4.0 m

= 60 ( m x m x m)

= 60 m3

Measurement 100 mL Graduated Cylinder Units of Measuring Volume Reading a Meniscus Units for Measuring Mass Quantities of Mass SI-English Conversion Factors Accuracy vs. Precision Accuracy Precision Resolution SI units for Measuring Length Comparison of English and SI Units Reporting Measurements Measuring a Pin Practice Measuring

100 mL Graduated Cylinder

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119

Instruments for Measuring Volume

Graduatedcylinder Syringe

Volumetric flaskBuret Pipet

Units of Measuring Volume

1 L = 1000 mL

1 qt = 946 mL

Timberlake, Chemistry 7th Edition, page 3

Reading a Meniscus

Units for Measuring Mass

1 kg = 2.20 lb

Timberlake, Chemistry 7th Edition, page 3

Quantities of Mass

Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 25

Earth’s atmosphere to 2500 km

Ocean liner

Indian elephant

Average human

1.0 liter of water

Grain of table salt

Typical protein

Uranium atomWater molecule

1024 g

1021 g

1018 g

1015 g

1012 g

109 g

106 g

103 g

100 g

10-3 g

10-6 g

10-9 g

10-12 g

10-15 g

10-18 g

10-21 g

10-24 g

Giga- Mega-

Kilo-Kilo-

base

milli-milli-

micro-

nano-

pico-

femto-

atomo-

SI-US Conversion FactorsRelationship Conversion Factors

Length

Volume

Mass

2.54 cm = 1 in.

1 m = 39.4 in.

946 mL = 1 qt

1 L = 1.06 qt

454 g = 1 lb

1 kg = 2.20 lb

1 in2.54 cm 39.4 in

1 m 1 m 39.4 in.

946 mL 1 qt

1 qt 946 mL

1.06 qt 1 L

1 L 1.06 qt

454 g 1 lb

1 lb 454 g

2.20 lb 1 kg

1 kg 2.20 lb

2.54 cm 1 in and

and

and

and

and

and

Accuracy vs. Precision

Random errors: reduce precision

Good accuracyGood precision

Poor accuracyGood precision

Poor accuracyPoor precision

Systematic errors: reduce accuracy

Accuracy Precision Resolution

subsequent samples

time

off

set

[arb

itrar

y un

its]

not accurate, not precise accurate, not precise not accurate, precise

accurate and precise accurate, low resolution

-2

-3

-1

0

1

2

3

SI System for Measuring Length

Unit Symbol Meter Equivalent _______________________________________________________________________

kilometer km 1,000 m or 103 m

meter m 1 m or 100 m

decimeter dm 0.1 m or 10-1 m

centimeter cm 0.01 m or 10-2 m

millimeter mm 0.001 m or 10-3 m

micrometer m 0.000001 m or 10-6 m

nanometer nm 0.000000001 m or 10-9 m

The SI Units for Measuring Length

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 118

Volume

calculated by multiplying L x W x H Liter the volume of a cube 1 dm (10 cm)

on a side so 1 L = 10 cm x 10 cm x 10 cm 1 L = 1000 cm3 1/1000 L = 1 cm3 1 mL = 1 cm3

Volume

1 L about 1/4 of a gallon - a quart 1 mL is about 20 drops of water or 1

sugar cube

Mass

weight is a force, is the amount of matter.

1gram is defined as the mass of 1 cm3 of water at 4 ºC.

1000 g = 1000 cm3 of water 1 kg = 1 L of water

Mass

1 kg = 2.5 lbs 1 g = 1 paper clip 1 mg = 10 grains of salt or 2 drops of

water.

Converting

k h D d c m how far you have to move on this chart,

tells you how far, and which direction to move the decimal place.

The box is the base unit, meters, Liters, grams, etc.

Conversions

Change 5.6 m to millimeters

k h D d c m

starts at the base unit and move three to the right.move the decimal point three to the right

56 00

Conversions

convert 25 mg to grams convert 0.45 km to mm convert 35 mL to liters It works because the math works, we are dividing

or multiplying by 10 the correct number of times

k h D d c m

Conversions

Change 5.6 km to millimeters

k h D d c m