##### Chemistry and Measurements

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1

Metric System

• the standard system of measurement in chemistry
2

International System of Units

• the official system of measurement throughout the world except for the United States
3

Length

• Metric System
• meter (m)
• SI
• meter (m)
4

Volume

• Metric System
• liter (L)
• SI
• cubic meter (m^3)
5

Mass

• Metric System
• gram (g)
• SI
• kilogram (kg)
6

Temperature

• Metric System
• degree Celcius
• SI
• kelvin (K)
7

Time

• Metric System
• second (s)
• SI
• second (s)
8

Meter

• one meter is equal to 39.4 inches
• 1 m = 100 cm
• 1 m = 39.4 in.
• 1 m = 1.09 yd
9

Centimeter

• a smaller unit of length
• commonly used in chemistry
• 2.54 cm = 1 in.
10

Volume

• the amount of space a substance occupies
• 1 qt = 946 mL
• 1 L = 1000 mL
• 1 L = 1.06 qt
11

Liter (L)

• slightly larger than a quart (qt)
• 1 L = 1000 mL
• 1 L = 1.06 qt
12

Milliliter (mL)

• smaller and more convenient
• commonly used in labs and hospitals
• 1000 mL = 1 L
13

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
• METRIC SYSTEM
• gram (g)
• used for smaller masses
• 1000 g = 1 kg
• 1 kg = 2.20 lb
• 454 g = 1 lb
14

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
15

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℉
• SI UNIT
• kelvin (K)
16

Time

• measured by second (s) on both systems
17

Measured Numbers

• the numbers you obtain when you measure a quantity
• SUCH AS:
• height
• weight
• temperature
18

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
19

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
20

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
21

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
22

Rules for Rounding Off

1. If the first digit to be dropped is 4 or less, then it and all the following digits are simply dropped from the number
2. If the first digit to be dropped is 5 or greater, then the last retained digit of the number is increased by 1
23

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
24

• When the calculator display contains fewer SFs than needed, add one or more significant zeros to obtain the correct number of significant figures
25

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
26

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)
27

Prefixes That Increase the Size of the Unit

• tera (T)
• numerical value: 1,000,000,000,000
• scientific notation: 1012
• equality: 1 Ts = 1 x 1012 s or 1 s = 1 x 10-12 Ts
• giga (G)
• numerical value: 1,000,000,000
• scientific notation: 109
• equality: 1 Gm = 1 x 109 m or 1 m = 1 x 10-12 Gm
• mega (M)
• numerical value: 1,000,000
• scientific notation: 106
• equality: 1 Mg = 1 x 106 g or 1 g = 1 x 10-6 Mg
• kilo (k)
• numerical value: 1,000
• scientific notation: 103
• equality: 1 km = 1 x 103 m or 1 m = 1 x 10-3 km
28

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 103 ms
• micro (µ*)
• numerical value: 0.000001
• Scientific notation: 10-6
• equality: 1 µg = 1 x 10-6 g or 1 g = 1 x 106 µg
• nano (n)
• numerical value: 0.000000001
• scientific notation: 10-9
• equality: 1 nm = 1 x 10-9 m or 1 m = 1 x 109 nm
• pico (p)
• numerical value: 0.000000000001
• scientific notation: 10-12
• equality: 1 ps = 1 x 10-12 s or 1 s = 1 x 1012 ps
29

Equalities

• show the relationship between two units that measure the same quantitiy
• 1 m = 100 cm.... = 1 x 102 cm
• 1 m = 1000 mm... 1 x 103 mm
• 1 cm = 10 mm... 1 x 101 mm
30

Cubic Centimeter

(abbreviated: cm3 or cc)

• the volume of a cube whose dimension are 1 cm on each side
• has the same volume as a millimeter
• 1 cm3 or cc = 1 mL
31

Measuring Mass

• 1 kg = 1000 g... = 1 x 103 g
• 1 g = 1000 mg... = 1 x 103 mg
• 1 g = 100 cg... = 1 x 102 cg
• 1 mg = 1000 mcg... = 1 x 103 mcg
32

Conversion Factors • any equality written as fraction, with one of the quantities in the numerator and the other in the denominator
33

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
34

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
35

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
36

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
37

Density • compares the mass of an object to its volume
38

Volume Displacement

• A solid
• completely emerged in eater displaces its own volume of water
• has a volume calculated from the volume difference