Chemistry and Measurements
Metric System
 the standard system of measurement in chemistry
International System of Units
 the official system of measurement throughout the world except for the United States
Length

Metric System
 meter (m)

SI
 meter (m)
Volume

Metric System
 liter (L)

SI
 cubic meter (m^3)
Mass

Metric System
 gram (g)

SI
 kilogram (kg)
Temperature

Metric System
 degree Celcius

SI
 kelvin (K)
Time

Metric System
 second (s)

SI
 second (s)
Meter
 one meter is equal to 39.4 inches
 1 m = 100 cm
 1 m = 39.4 in.
 1 m = 1.09 yd
Centimeter
 a smaller unit of length
 commonly used in chemistry
 about equal to the width of your little finger
 2.54 cm = 1 in.
Volume
 the amount of space a substance occupies
 1 qt = 946 mL
 1 L = 1000 mL
 1 L = 1.06 qt
Liter (L)
 slightly larger than a quart (qt)
 1 L = 1000 mL
 1 L = 1.06 qt
Milliliter (mL)
 smaller and more convenient
 commonly used in labs and hospitals
 1000 mL = 1 L
Mass of an Object
 a measure of the quantity of material it contains

SI UNIT
 kilogram (kg)
 used for larger masses, such as body mass
 kilogram (kg)

METRIC SYSTEM
 gram (g)
 used for smaller masses
 gram (g)
 1000 g = 1 kg
 1 kg = 2.20 lb
 454 g = 1 lb
Weight
 a measure of the gravitational pull on an object

EXAMPLE:
 an astronaut with a mass of 75.0 kg has a weight of 165 lb
Temperature
 tells us how hot or cold something is

METRIC SYSTEM
 celsius (℃)
 water freezes at 0℃ and boils at 100℃
 whereas on the Fahrenheit scale, water freezes at 32℉ and boils at 212℉
 celsius (℃)

SI UNIT
 kelvin (K)
Time
 measured by second (s) on both systems
Measured Numbers
 the numbers you obtain when you measure a quantity

SUCH AS:
 height
 weight
 temperature
Significant Figures
 SIGNIFICANT FIGURE RULES:
 all the digits including the estimated digit
 all nonzero digits and zeros between digits
 zeros at the end of a decimal number

A ZERO IS NOT A SIGNIFICANT FIGURE
 at the beginning of a decimal number
 used as a placeholder in a larger number without a decimal point
 not zeros that act as placeholders before digits
Scientific Notation and Significant Zeros
 when one or more zeros in a large number are significant, they are shown clearly by writing the number in scientific notation
Exact Numbers
 numbers obtained by counting items
 not measured
 do not have limited number of significant figures
 do not affect the number of significant figures in a calculated answer
Examples of Some Exact Numbers
 8 doughnuts
 2 baseballs
 5 capsules
 1 L = 1000 mL
 1 m = 100 cm
 1 kg = 1000 g
 1 ft = 12 in
 1 qt = 4 cups
 1 lb = 16 oz
Rules for Rounding Off
 If the first digit to be dropped is 4 or less, then it and all the following digits are simply dropped from the number
 If the first digit to be dropped is 5 or greater, then the last retained digit of the number is increased by 1
Multiplication and Division with Measured Numbers pg. 32
 In multiplication or division, the final answer is written so that it has they same number of significant figures as the measurement with the fewest significant figures
Adding Significant Zeros pg. 32
 When the calculator display contains fewer SFs than needed, add one or more significant zeros to obtain the correct number of significant figures
Addition and Subtraction with SFs pg.32
 In addition or subtraction, the final answer is written so that it has the same number of decimal places as the measurement with the fewest decimal places
Prefix
 can be placed in front of any unit to increase or decrease its size by some factor of 10

EXAMPLES:
 milli....milligram (mg)
 micro....microgram (mcg)
Prefixes That Increase the Size of the Unit
 tera (T)
 numerical value: 1,000,000,000,000
 scientific notation: 10^{12}
 equality: 1 Ts = 1 x 10^{12} s or 1 s = 1 x 10^{12} Ts
 giga (G)
 numerical value: 1,000,000,000
 scientific notation: 10^{9}
 equality: 1 Gm = 1 x 10^{9} m or 1 m = 1 x 10^{12} Gm
 mega (M)
 numerical value: 1,000,000
 scientific notation: 10^{6}
 equality: 1 Mg = 1 x 10^{6} g or 1 g = 1 x 10^{6 } Mg
 kilo (k)
 numerical value: 1,000
 scientific notation: 10^{3}
 equality: 1 km = 1 x 10^{3} m or 1 m = 1 x 10^{3} km
Prefixes That Decrease the Size of the Unit
 deci (d)
 numerical value: 0.1
 scientific notation: 10^{1}
 equality: 1 dL = 1 x 10^{1} L or 1 L = 10 dL
 centi (c)
 numerical value: 0.01
 scientific notation: 10^{2}
 equality: 1 cm = 1 x 10^{2} m or 1m = 100 cm
 milli (m)
 numerical value: 0.001
 scientific notation: 10^{3}
 equality: 1 ms = 1 x 10^{3} s or 1 s = 1 x 10^{3} ms
 micro (µ*)
 numerical value: 0.000001
 Scientific notation: 10^{6}
 equality: 1 µg = 1 x 10^{6} g or 1 g = 1 x 10^{6} µg
 nano (n)
 numerical value: 0.000000001
 scientific notation: 10^{9}
 equality: 1 nm = 1 x 10^{9} m or 1 m = 1 x 10^{9} nm
 pico (p)
 numerical value: 0.000000000001
 scientific notation: 10^{12}
 equality: 1 ps = 1 x 10^{12} s or 1 s = 1 x 10^{12} ps
Equalities
 show the relationship between two units that measure the same
quantitiy
 1 m = 100 cm.... = 1 x 10^{2} cm
 1 m = 1000 mm... 1 x 10^{3} mm
 1 cm = 10 mm... 1 x 10^{1} mm
Cubic Centimeter
(abbreviated: cm^{3} or cc)
 the volume of a cube whose dimension are 1 cm on each side
 has the same volume as a millimeter
 1 cm^{3} or cc = 1 mL
Measuring Mass
 1 kg = 1000 g... = 1 x 10^{3} g
 1 g = 1000 mg... = 1 x 10^{3} mg
 1 g = 100 cg... = 1 x 10^{2} cg
 1 mg = 1000 mcg... = 1 x 10^{3} mcg
Conversion Factors
 any equality written as fraction, with one of the quantities in the numerator and the other in the denominator
Equalities (conversion)
 uses two different units to describe the same measure amount
 written for relationship between units of the metric system, U.S. units, or between metric and U.S. units

EXAMPLES:
 1 m = 1000 mm
 1 lb = 16 oz
 2.20 lb = 1 kg
Equalities: Conversion Factors & SF
 the numbers in:
 any equality between two metric units or between two U.S system units are obtained by definition and are exact number
 a definition are exact and are not used to determine SFs
 an equality between metric and U.S units contain one number obtained by measurement and count toward the significant figures
 Exception: The equality 1 in. = 2.54 cm has been defined as an exact relationship, 2.54 is an exact number
Conversion Factors From a Percentage
 a percent factor gives the ratio of the parts to the whole and
uses
 the same unit in the numerator and denominator
 uses the value of 100 and can be written as two factors
Problem Solving Using Unit Conversion
 requires one or more conversion factors to change a given unit to the needed unit

problem solving requires indentification of:
 the given quantity units
 the units needed
 conversion factors that connect the given and needed units
 given unit x one or more conversion factors = needed unit
Density
 compares the mass of an object to its volume
Volume Displacement
 A solid
 completely emerged in eater displaces its own volume of water
 has a volume calculated from the volume difference