Chapter 1 Introduction to Chemistry
description
Transcript of Chapter 1 Introduction to Chemistry
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Daniel L. RegerScott R. GoodeDavid W. Ball
www.cengage.com/chemistry/reger
Chapter 1 Introduction to Chemistry
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What is Science?
“Natural abilities are like natural plants; they need pruning by study.” – Sir Francis Bacon (1561-1626)
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• Definitions• Science: knowledge
• Sir Francis Bacon: “And thus knowledge itself is power”• Modern science, the acquisition of knowledge,
is acquired by experience (experiment)
• Chemistry: the study of matter and its interactions with other matter and with energy.
The Nature of Science and Chemistry
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Chemistry and the Natural Sciences
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• Scientific method: investigations that are guided by theory and earlier experiments.
• Hypothesis: a possible explanation for an event.
• Law: a statement that summarizes a large number of observations.
• Theory: an explanation of the laws of nature.
The Scientific Method
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• Matter: anything that has mass and occupies space.
• Mass: the quantity of matter in an object.• Weight: the force of attraction between
an object and other objects.
Matter
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Mass on moon and earth is the same.
Weight on moon and earth is the different.
Mass and Weight
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• Property: anything observed or measured about a sample of matter.
• Extensive property: depends on the size of the sample.• mass, volume
• Intensive property: independent of sample size.• density, color, melting or boiling point
Properties of Matter
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• Physical properties: can be measured without changing the composition of the sample.• mass, density, color, melting point
• Physical change: a change that occurs without changing the composition of the material.• freezing, melting
Physical Properties and Changes
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• Chemical properties: describe the reactivity of a material.• Natural gas burns in air; iron rusts.
• Chemical change: at least part of the material is changed into a different kind of matter.• The digestion of sugar is a chemical
change.
Chemical Properties
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Practice
State if the underlined property or changes is intensive or extensive and chemical or physical.
a) The color of mercury is silvery.b) The sample of iron rusts by reaction with oxygen.c) The heat released by burning coal can power a city.d) Water boils at 100°C.e) A new pencil is 10 inches long.
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• Substances - a material that is chemically the same throughout.• Two types of substances• Elements cannot be broken into simpler
substances.• Compounds can be broken down into
elements.
Classification of Matter
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• Substance: cannot be separated into component parts by physical methods.
• Compound: a substance which can be separated into simpler substances by chemical methods.
• Element: a substance which cannot be separated into simpler substances by chemical methods.
Substances
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• Mixture: matter that can be separated into simpler materials by physical methods.• Heterogeneous mixture: composition of the
mixture changes from one part to another.• Homogeneous mixture or solution:
composition of the mixture is uniform throughout.
• Alloy: a solution of a metal and another material (usually another metal).
Mixtures
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Classification of Matter
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Practice
Identify the following types of matter as elements, compounds, heterogeneous mixtures, or homogeneous mixtures.
a)Sodium chloride
b)Stainless steel
c)Chlorine
d)soil
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Measurement
• Most modern science depends on measurements• Parts of a measurement• The object of the measurement• The value of the measurement• The units of the measurement• The reliability of the measurement
• Example “The mass of iron was 4.0501 grams
• All parts MUST be present in an answer for complete credit!!
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• Modern chemistry is largely based on experimental measurements. The confidence in measurements involves:• Accuracy: agreement of a measurement
with the true value.• Precision: agreement among repeated
measurements of the same quantity.
Accuracy and Precision
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accurate and
precise
precise but not
accurate
accurate but not precise
neither accurate
nor precise
Accuracy and Precision
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Accuracy and Precision
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• The number of significant figures is the number of digits from the first non-zero digit through the last reported digit.• The uncertainty is at least ±1 unit in the last
reported digit.• Leading zeros – zeros preceding the first
non-zero digit are NEVER significant. • Trailing zeros – a decimal point is the key.
• No decimal – trailing zeros are NOT significant• Decimal – trailing zeros ARE significant
Significant Figures
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• Quantities that are not limited by significant figures:• counted numbers or tallies.• defined numbers.• the power of ten in exponential notation.
Significant Figures
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• How many significant figures are present in each of the measured quantities?
• 0.00121062006900.01.00120.001060
Significant Figures
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• Since trailing zeros in numbers without a decimal points may be confusing for significant figures use scientific notation.
• 100 1? Or should there have been a decimal?
1 x 102 11.0 x 102 21.00 x 102 3
Significant Figures
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•Determine the number of significant figures:
100. 100.030505 437,000125,904,000 4.80 x 10-3
4.800 x 10-3 0.0048
Practice
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• The absolute uncertainty can be no smaller than the least accurate number.
• 12.02 - 10.4
1.62 • 1.6 • The answer should have no more
decimal places than the least accurate number.
Uncertainty in Addition and Subtraction
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• Answers should have no more significant figures than the least accurate number.
• 3121 x 12 = 37452 = 3.7 x 104
# sig. digits 4 x = =
NOT 37!!!!!!
37000 is questionable
2 2 2
Uncertainty in Multiplication and Division
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• Determine accuracy in the same order as the mathematical operations, # of significant digits are in red.
• density = 3.7 g/mL
• Be mindful of what your calculator gives you!!
3
2
2.79 g
8.34 mL - 7.58 mLv
m 2.79 g
0.76mL=
33
3
2
=
Mixed Operations
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Rounding
• Be cautious about rounding during multiple steps.• Keep more significant figures than you
need in intermediate steps.• Ex:• 2.5 x 4.50 x 11.25 = ?
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• Evaluate each expression to the correct number of significant figures.(a) 4.184 x 100.620 x (25.27 - 24.16)
(b)
(c)
8.925 - 8.904x 100%8.925
9.6 x 100.65
8.321+ 4.026
Practice
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Calculate each to the correct number of significant figures .a) 0.1654 + 2.07 - 2.114 b) 8.27 x (4.987 - 4.962)
c)
d)
9.5 + 4.1 + 2.8 + 3.175
4 (4 is exact)
x 100%9.025 - 9.024
9.025
Practice
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Quantity Unit Abbreviation
Length meter m
Mass kilogram kg
Time second s
Temperature kelvin K
Amount mole mol
Electric current ampere A
Luminous intensity candela cd
Base Units in the SI
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Prefix Abbreviation Meaning
mega- M 106
kilo- k 103
centi- c 10-2
milli- m 10-3
micro- 10-6
nano- n 10-9
pico- p 10-12
Common Prefixes Used With SI Units
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1 kilogram
is
equal
to
1000 g.
Prefixes Used With SI Units
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• Unit conversion factor: a fraction in which the numerator is a quantity equal or equivalent to the quantity in the denominator, but expressed in different units
• The relationship 1 kg = 1000 g• Generates two unit conversion factors:
1kg
g 1000 and
g 1000
kg 1
Unit Conversion Factors
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Unit Conversions
• Lets convert 5.73 g to kg.• Start with what you know!!!• Add conversion factors to cancel units• Units must be same on top & bottom to cancel
g
kgg
1000
173.5
grams on topgrams on bottom
0.00573 kg
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Practice
Convert the following:
a)17.43 km to cm
b)165 μg to kg
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• Volume is the product of three lengths.• The standard unit of volume is the cubic
meter (m3).100 cm = 1 m(100 cm)3 = (1 m)3
106 cm3 = 1 m3
• Two important non-SI units of volume are the liter and milliliter.1 liter (L) = 1000 mL = 1000 cm3
1 mL = 1 cm3
Conversion Among Derived Units
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Volumes can be expressed in different units depending on the size of the object.
1 m3 contains1000 L
1 L contains1000 mL
Volume
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• Express a volume of 1.250 L in mL, cm3, and m3
33-36
3
33
m10 1,250cm 10
m 1 L 1.250
cm 1,250L 1cm 1000
L 1.250
mL 1,250L 1mL 1000
L 1.250
Using Unit Conversions
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• Density: mass per unit volume
•
• Density, in SI base units, is kg/m3 (kg m-3).
• Most commonly used density units are g/cm3 (g cm-3 or g/mL) for solids and liquids, and g/L for gases.
Vm
d
Density
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• The density of Ti is 4.50 g/cm3 or 4.50 g = 1 cm3.
• Calculate the volume of 7.20 g Ti.
Conversions Between Equivalent Units
Ti cm 1.60g 4.50
cm 1 Ti g 7.20 3
3
Units cancel
What we knowAnswer:
√ number√ units√ object√ sig figs
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English System
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Practice
a) Express 323 milliliters in gallons.
b) Express 3.61 cubic feet in cubic centimeters.
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273.15TT
F1.8
C1.0F32TT
F32C1.0
F1.8TT
CK
o
oo
FC
oo
o
CF
0 Kelvin 273 373
-273o Celsius 0o 100o
-460o Fahrenheit 32o 212o
For water
Temperature Conversion Factors
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• Express 17.5°C in °F and in K.
Practice
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Practice• It has been estimated that 1.0 g of seawater contains 4.0 pg
of Au. The total mass of seawater in the oceans is 1.6x1012 Tg, If all of the gold in the oceans were extracted and spread evenly across the state of Georgia, which has a land area of 58,910 mile2, how tall, in feet, would the pile of Au be?Density of Au is 19.3 g/cm3. 1.0 Tg = 1012g.
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Practice• One metal object is a cube with edges of 3.00 cm and a mass
of 140.4 g. A second metal object is a sphere with radius 1.42 cm and a mass of 61.6 g. Are these objects made of the same or different metals? Assume the calculated densities are accurate to 1.00%.
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Practice
A 40-lb container of peat moss measures 14 x 20 x 30 in. A 40-lb container of topsoil has a volume fo 1.9 gal. •Calculate the density of both the peat moss and the topsoil.•How many bags of peat moss are needed to cover an area measuring 10 ft x 20 ft x 2 in?
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PracticeOn a typical day, a hurricane expends the energy equivalent to the explosion of two thermonuclear weapons. A thermonuclear weapon has the explosive power of 1.0 Mton of nitroglycerin. Nitroglycerin generates 7.3 kJ of explosive power per gram of nitroglycerin. The hurricane’s energy comes from the evaporation of water that requires 2.3 kJ per gram of water evaporated. How many gallons of water does a hurricane evaporate per day?
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THINK!!
Homework:OWL: All of the required assignmentsbook: All questions from the end of the chapter are
recommended as practice.