Transcript AP Chem Chapter 1 - hermansenssciencespace

Chapter 1
Chemical Foundations
AP Chemistry
Objectives
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Recall units of measure
Describe uncertainty in measurement
Use scientific notation for numbers
Apply significant figure rules
Units of Measure
• SI Base Units
– Mass
• Kilogram – kg
• 1 kilogram is about 2.20 pounds
– Length
• Meter – m
• 1 meter is about 3 feet
Units of Measure
• Time
– Second – s
– The time needed for a cesium-133 atom
to perform 9,192,631,770 complete
oscillations.
• Temperature
– Kelvin – K
– 273 K = 0 degrees C
• Amount
– Mole – mol
– 1 mol = 6.022x1023 particles
Units of Measure
• Current
– Ampre – A
• Luminous Capacity
– Candela – cd
• First five are the most commonly used in
chemistry
Volume
• Volume is not an SI Base Unit
– Metric system
– Powers of 10
• 1 Liter is 1/1000 of a cubic meter
• 1 Liter (L) = 1000 cm3 = 1000 mL
Cubic Meter
Liter
Milliliter
Volume?
• Uncertainty is in the last digit.
Accuracy and Precision
• Accuracy
– The nearness of a measurement to its
accepted value
• Precision
– The agreement between numerical values
– You can be precise without being accurate
Accurate &
Precise
Precise
Neither
• Loss of accuracy due to systematic errors
– Error in same direction every time
• Random Error give erratic results
– Poor technique
Significant Figures
• All known digits plus one estimated digit in
a measurement
What is the length?
• 2 Sig. Fig
• 1 Known Digit
• 1 Estimated Digit
Significant Figures
• Rule #1
– All Nonzero digits are significant
– Ex. 76.44 mL
– Ex. 285.85 s
Significant Figures
• Rule #2
• “Captive Zeros”
• Zeros appearing between nonzero digits
are significant
• Ex. 308.2001 g =
Significant Figures
• Rule #3
• “Leading Zeros”
• Zeros appearing in front of nonzero digits
are not significant
• Ex. 0.007036 g
• Takes care of unit changes
Significant Figures
• Rule #4
• “Ending Zeros”
• Ending zeros are significant if there is a
decimal place
• Ex. 53.00 m
• Ex. 40000. m
• Ex. 40000 m
• 40000. is much more precise than 40000
What is the length?
Significant Figures
• Rule #5
• “Exact Numbers”
• Exact number have an unlimited number
of significant figures
• Exact numbers are counting numbers or
definitions
• 2 cars or 1000g/1kg
Significant Figures
• Rule #6
• “Scientific Notation”
• All numbers that come before the x10n are
significant
– Must be in proper form
• Ex. 3.33x105
• Ex. 2.04x10-4
Rounding
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5 and larger round up
4 and smaller round down
Round the following
34.567 to 2 SF =
756.44 to 4 SF =
0.004325 to 3 SF =
3436543 to 2 SF =
Addition and Subtraction w/ SF
• Addition and Subtraction
– The answer must have the same
number of digits to the right of the
decimal as there are in the
measurement having the fewest digits to
the right of the decimal point
– Ex. 12.11 m + 15 m =
– Number of SF’s does not matter!
Multiplication and Division w/ SF
• Multiplication and Division
– The answer can have no more SF’s than
are in the measurement with the fewest
total SF’s
– Ex. 55 m / 11.34 s =
Scientific Notation
• A method of representing very large or
very small numbers
• M x 10n
– M is a number 1 or larger and less than
10
– n is an integer (positive or negative)
– All digits in M are significant (If in proper
form)
Converting to Sci. Notation
• Move decimal so that M is between 1 and
10
• Determine n by counting the number of
places the decimal point was moved
– Moved to the left, n is positive
– Moved to the right, n is negative
Examples
• 340,000,000 =
• 5.04x105 =
• 0.00000300 =
• 2.212x10-4 =
Sci. Notation on Calculators
• Enter digits in you calculator using the EE
key.
• For TI 83’s it is the 2nd of the comma
• For TI 30’s it is a key
• Saves key strokes
• Fewer OOR mistakes
• 3.4x106 = 3.4E6
• 7.4x10-5 = 7.4E-5
Sci. Notatation Math Operations
• Multiply and Divide
– Multiply or divide first number
– Add exponents (Multiply)
– Subtract exponents (Divide)
• Addition and Subtraction
– Exponents must be the same
– Then add or subtract first number
– Exponents stay the same
Calculations
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3.0x105 + 4.0x105 =
4.0x103 – 2.0x102 =
7.0x105 * 2.0x104 =
8.0x106 / 4.0x10-3 =
• _____4.5x104____ =
6.2x106 * 3.1x10-8
Objectives
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Recall metric prefixes
Convert numbers from one unit to another
Describe different temperature scales
Explain density and perform calculations
Classify matter into groups
The Metric System
• A system based on powers of ten
• Uses SI Units
• Allows easy work with both large and
small numbers
• Prefixes tell us which power of 10 we are
using
SI Prefixes (10x larger)
Page 9 in your book
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Tera
Giga
Mega
Kilo
Hecto
Deca
Base
T
G
M
k
h
da
1012
109
106
103
102
101
100
1000000000000
1000000000
1000000
1000
100
10
1
SI Prefixes (10x smaller)
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Base
Deci
Centi
Milli
Micro
Nano
Pico
d
c
m
μ
n
p
100
10-1
10-2
10-3
10-6
10-9
10-12
1
.1
.01
.001
.000001
.000000001
.000000000001
Conversions
• To convert between units set up
conversion factors
– Ratios of equality
3
1000mm 1x10 m
1m
1km
Convert
67 kg to g
Convert
450 cL to dL
Convert
8
3.4x10 ng to kg
Converting From Metric To English
• Find ratios that are true
– Page 18 has some equivalents
39.4in 2.54cm
1in
1m
Convert
763 cm to yd
Convert
1.2 mi/hr to ft/s
Convert
2
2
3.8 m /hr to cm /s
Temperature
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Many different temp. scales
All 0 marks based on different ideas
0 ºF Coldest saltwater stays a liquid
0 ºC Normal Freezing Point of water
0 K Molecular motion stops
1 K = 1 ºC = 1.8 ºF
Temperature Conversion
• Temp K = 273 + Temp C
• Temp C = Temp K – 273
• 0 ºC = 273 K
• If you need any others look up the equ.
• TC= (TF – 32)(5/9)
• TF = TC(9/5) + 32
Density
• Ratio of mass to volume
• Density = __Mass__
Volume
• Periodic Trend
• Units
– Solids – g/cm3
– Liquids – g/mL
– Gases – g/L
Density Determination
• Mass is determined on a balance
• Volume is measured in two ways
– Regular objects can be measured
– All objects can use water displacement
Density
• Physical Property
– Can be used to identify a substance
Lead 11.35
Iron 7.87
Magnesium 1.74
Zinc 7.13
Copper 8.96
Example: A metal cube has sides
measuring 3.00 cm. It has a mass of
242.13g. What is the density?
What is the metal?
Density
• Physical Property
– Can be used to identify a substance
Lead 11.35
Iron 7.87
Magnesium 1.74
Zinc 7.13
Copper 8.96
Homework
• p.33 #'s 33a-f,36a-d,42 47,57,68