Chemistry Conversions

Dimensional Analysis and Atoms, Elements, Compounds

SI PrefixesPrefix Abbreviation Exponential

MultiplierMeaning Example using length

Kilo- k 103 1000 1 kilometer (km) = 1000 m

Hecto- h 102 100 1 hectometer (hm) = 100 m

Deka- da 101 10 1 dekameter (dam) = 10 m

100 1 1 meter (m)

Deci- d 10-1 1/10 1 decimeter (dm) = 0.1 m

Centi- c 10-2 1/100 1 centimeter (cm) = 0.01 m

Milli- m 10-3 1/1000 1 millimeter (mm) = 0.001 m

Converting From One Unit to Another

• We will convert A LOT!

• Uses a technique called Factor Label Method

• Cancels out units and does the math for you!!

Factor-Label Method for Conversions

• Mathematics used Numbers, rather than Quantities

• Chemistry uses these same Numbers along with the value’s Units

• A Number is useless without its unit

• Units give the Number an actual meaning

Conversion Factors• A conversion Factor is needed to go from one unit

to another• You must first know how much of one thing is of

another before making any conversions• We all know 1 foot is made up of 12 inches

SO…• The conversion factor needed to go from feet to

inches or from inches to feet is 1 foot / 12 inches or 12 inches / 1 foot,

Respectively.

Conversion Factors

Let’s try using 1 pound = 0.454 Kilograms

1 inch = 2.54 centimeters1 gallon = 3.71 Liters

1 mile = 1.61 Kilometers

Conversions

1 pound = 0.454 Kg

157 lb

1 lb

0.454 kg

The “Heart” of the problem is where the conversion actually takes place. This is where your conversion factor does its work.

Conversions

1 pound = 0.454 Kg

157 lb

1 lb

0.454 kg

( 157 * 0.454 ) / 1 = 71

= 71 kgSo yes, with the proper units 157 lb does equal 71 kg, but without units the values are not the same, as we do not know the correct representation numbers.

Units

• Units are everything. They give any value an actual meaning and interpretation.

• Always carry your units through, rewriting them until you reach a final value, or you will be lost.

English System (American System)

• 1 foot = 12 inches• 1 yard = 3 feet• 1 mile = 5,280 feet = 1,760 yards• 1 gallon = 16 cups = 4 quarts = 8 pints• 1 pound = 16 ounces

Conversions Factors:

Converting with English Units

Convert 15.41 yards to inches:

Conversion Factors:• 1 yard = 3 feet• 1 foot = 12 inches

Question:

Converting with Metric Units

Convert 15.41 yards to inches:

15.41 yd

Conversion Factors:• 1 yard = 3 feet• 1 foot = 12 inches

Converting with Metric Units

Convert 15.41 yards to inches:

15.41 yd1 yd3 ft

Conversion Factors:• 1 yard = 3 feet• 1 foot = 12 inches

Converting with Metric Units

Convert 15.41 yards to inches:

15.41 yd1 yd3 ft 12 in.

1 ft

Conversion Factors:• 1 yard = 3 feet• 1 foot = 12 inches

Converting with Metric Units

Convert 15.41 yards to inches:

15.41 yd1 yd3 ft 12 in.

1 ft

= (15.4 * 3 * 12) / 1

15.41 yards = 554.76 inches

Metric System

Common Metric Prefixes:Prefix Abbreviation Value (Base Unit)

Kilometer km 1000

Hectometer hm 100

Dekameter dam 10

Base Unit (meter) meter 1

Centimeter cm 0.01

Millimeter mm 0.001

Micrometer µm 0.000001

Converting with Metric Units

Convert 0.248 km to centimeters:Conversion Factors:• 1 Kilometer = 1000 meters• 1 meter = 100 centimeters

Question:

Prefix Abbreviation Value (Base Unit)Kilometer km 1000Hectometer hm 100Dekameter dam 10Base Unit (meter) meter 1Centimeter cm 0.01Millimeter mm 0.001Micrometer µm 0.000001

Converting with Metric Units

Covert 0.248 km to centimeters:

0.248 km

Conversion Factors:• 1 Kilometer = 1000 meters• 1 meter = 100 centimeters

Converting with Metric Units

Covert 0.248 km to centimeters:

0.248 km1 km

1000 m

Conversion Factors:• 1 Kilometer = 1000 meters• 1 meter = 100 centimeters

Converting with Metric Units

Convert 0.248 km to centimeters:

0.248 km1 km

1000 m1m

100 cm

Conversion Factors:• 1 Kilometer = 1000 meters• 1 meter = 100 centimeters

Converting with Metric Units

Convert 0.248 km to centimeters:

0.248 km1 km

1000 m1m

100 cm

= (0.248 * 1000 * 100) / 1

= 24,800 centimeters

Much Easier!

Calculations: Metric Vs. American System?

Prefix Abbreviation Value (Base Unit)

Kilometer km 1000

Hectometer hm 100

Dekameter dam 10

Base Unit (meter) meter 1

Centimeter cm 0.01

Millimeter mm 0.001

Micrometer µm 0.000001

Just count the zeros and move the decimal spot to the left or the right.