1. 2.1 Measurement Systems
Measurement is the determination of the dimensions, capacity, quantity, or extent of something.
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2. 2.1 Measurements in Chemistry
always consists of two parts
NUMBER
EXACT or INEXACT
SIGNIFICANT FIGURES
SCIENTIFIC NOTATION
UNIT
METRIC SYSTEM
DIMENSIONAL ANALYSIS
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3. 2.1 Metric System Units System Internationale (SI)
Mass kilogram (kg), gram (g)
Length meter (m), centimeter (cm)
Volume cubic meter (m3),
cubic centimeter (cm3)
liter (L) = 1000 cm3 (exact)
milliliter (mL) = 1 cm3 (exact)
Time second (s)
Temperature kelvin (k)
Celsius (ºC)
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4. Numerical prefixes for larger or smaller units:
Common Metric System Prefixes with Their Symbols and Mathematical Meanings.
Numerical prefixes for larger or smaller units:
mega (M) times unit (106)
kilo (k) 1000 times unit (103)
deci (d) 0.01 times unit (10-1)
centi (c) 0.01 times unit (10-2)
milli (m) times unit (10-3)
micro (µ) times unit (10-6)
My King Died Chewing M & M’s
Memorize these!
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5. Figure 2. 2. Comparisons of the base metric system
Figure 2.2 Comparisons of the base metric system units of length (meter), mass (gram), and volume (liter) with common objects.
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6. Derived Units in the Metric System.
Frequency (cycles/s, hertz)
Density (mass/volume, g/cm3)
Speed (distance/time, m/s)
Acceleration (distance/(time)2, m/s2)
Force (mass x acceleration, kg•m/s2, newton)
Pressure (force/area, kg/(m•s2), pascal)
Energy (force x distance, kg•m2/s2, joule)
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7. 2.3 Exact and Inexact Numbers
Have no uncertainty associated with them
From measurement of indivisible objects
10 tennis balls
29 students enrolled
Some conversion factors
Exactly 2.54 centimeters = one inch
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8. 2.3 Exact and Inexact Numbers
Have some uncertainty associated with them
From scalar measurements
“Stuff” rather than “Things”
Values are limited by the instrument
14.3 gallons ( 6 oz)
gallons ( 1 tsp)
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9. 2.4 Uncertainty in Measurement and Significant Figures
Significant figures (sig figs or sig digs) are the digits in an inexact number.
The last digit in an inexact number is an estimated value.
The number of sig figs depends upon the instrument used.
14.3 gallons gallons
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10. 2.4 Uncertainty in Measurement and Significant Figures
Exact numbers have an infinite number of significant figures. They do not contain an estimated value.
10 tennis balls
2.54 cm = 1 inch
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11. 2.5 Significant Figures and Mathematical Operations
When is zero a significant figure?
Trailing zeros are always sig. figs.
____ sig. figs.
____ sig. figs.
Trailing zeros are significant because they are the best estimate of the value.
(best estimate)
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12. 2.5 Significant Figures and Mathematical Operations
When is zero a significant figure?
Embedded zeros are always sig. figs.
____ sig. figs.
____ sig. figs.
Leading zeros are never sig. figs.
____ sig. figs.
____ sig. figs.
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13. Chemistry at a Glance: Significant Figures
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14. 2.5 Significant Figures and Mathematical Operations
Multiplication and Division
The result can have no more sig. figs. than the fewest number of sig. figs. used to obtain the result.
4.242 x =
12.24 / 2.0 =
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15. 2.5 Significant Figures and Mathematical Operations
Addition and Subtraction
Result will have a digit as far to the right as all the numbers have a digit in common
6.9463
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16. 2.5 Significant Figures and Mathematical Operations
Rounding Off
When the last sig. fig. is followed by a number equal to or greater than 5, round the last sig. fig. up.
When the last sig. fig. is followed by a number less than 5, leave the last sig. fig. as is.
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17. 2.6 Scientific Notation Used for very large or very small numbers
Distance from earth to sun
93,000,000 miles
Diameter of a carbon atom
meters
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18. 2.6 Scientific Notation
An ordinary decimal number is expressed as the product of a coefficient between 1 and 10, and an exponential term.
Express in scientific notation:
93,000,000 miles
meters
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19. 2.6 Scientific Notation
Scientific notation is useful for handling significant figures.
Give the result to the proper number of significant figures:
( – ) x x 430 =
 45.0 =
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20. 2.7 Conversion Factors and Dimensional Analysis
A conversion factor is a ratio that specifies how one unit of measurement is related to another:
1 inch = cm
_1 in__ 2.54 cm
2.54 cm in
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21. 2.7 Conversion Factors and Dimensional Analysis
Dimensional analysis is a problem-solving method in which the units of the meas-urement are used to set up the calcula-tion.
Units behave like numbers, they can be multiplied, divided, or cancelled.
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22. 2.7 Conversion Factors and Dimensional Analysis
What is the volume of a cube if its edges are 2.5 cm long?
How long is a foot in centimeters?
Convert mm to m.
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23. 2.7 Conversion Factors and Dimensional Analysis
How many miles will I travel in 3.00 hours at 65.0 miles per hour?
How long will it take to travel 500 miles at 65 miles per hour?
What is my speed, in miles per hour, if I ride my bike 25.5 miles in 1.20 hours?
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24. 2.8 Density Matter has mass and volume.
Density is the ratio of mass to volume for a specific type of matter.
Density = _mass_ _grams_
volume milliliters
Density is a characteristic property of a pure substance.
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25. Left: Shortening floats on water. Right: Copper floats on mercury
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26. Liquids that do not dissolve in one another and that have different densities float on one another, forming layers.
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27. Table 2.3 Densities of Selected Substances
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28. 2.8 Density
Water has a density of 1.00 g/mL at 20°C. What is the mass of 20.0 mL of water?
20.0 mL of gasoline has a mass of 11.2 g. What is its density?
What volume of ethyl alcohol will have a mass of 20.0 g? Its density is 0.79 g/mL.
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29. 2.9 Temperature Scale and Heat Energy
Heat is a form of energy. Temperature can be used to measure heat.
1 calorie = amount of heat required to raise temperature of 1 gram of water by 1 Celcius
1 Calorie = 1000 calories = 1 kcal
1 Calorie = Joule
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30. The relationships among the Celsius, Kelvin, and Fahrenheit temperature scales are determined by the degree sizes and the reference point values.
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