Chapter 1
Introduction:
Matter and Measurement
▶ THE BEAUTIFUL COLORS
that develop in trees in the fall
appear when the tree ceases
to produce chlorophyll, which
imparts the green color to the
leaves during the summer.
Some of the color we see has
been in the leaf all summer,
and some develops from the
action of sunlight on the leaf
as the chlorophyll disappears.
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Introduction: Matter and Measurement
What’s Ahead
1.1 THE STUDY OF CHEMISTRY
We begin with a brief description of what chemistry is, what chemists do, and why it is
useful to learn chemistry.
1.2 CLASSIFICATIONS OF MATTER
Next, we examine some fundamental ways to classify matter, distinguishing between
pure substances and mixtures and between elements and compounds.
1.3 PROPERTIES OF MATTER
We then consider different characteristics, or properties, used to characterize, identify,
and separate substances.
1.4 UNITS OF MEASUREMENT
We observe that many properties rely on quantitative measurements involving numbers
and units. The units of measurement used throughout science are those of the metric
system.
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Introduction: Matter and Measurement
What’s Ahead
1.5 UNCERTAINTY IN MEASUREMENT
We observe that the uncertainty inherent in all measured quantities is expressed by the
number of significant figures used to report the quantity. Significant figures are also used
to express the uncertainty associated with calculations involving measured quantities.
1.6 DIMENSIONAL ANALYSIS
We recognize that units as well as numbers are carried through calculations and that
obtaining correct units for the result of a calculation is an important way to check
whether the calculation is correct.
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Introduction: Matter and Measurement
Chemistry
• Chemistry is the study of
matters and the changes
that matter undergoes.
• One of the joys of
learning chemistry is
seeing how do chemical
principles operate in all
aspects of our lives.
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Chemistry
1.1 THE STUDY OF CHEMISTRY
• Chemistry is the study of the properties and behavior of
matter.
• It is central to our
fundamental
understanding of
many sciencerelated fields.
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1.1 THE STUDY OF CHEMISTRY
Chemistry and the Chemical Industry
• Worldwide sales of chemical products: $585 billion/yr (U.S.)
• Chemical industry employs >10% of all scientists/engineers.
Figure 1.3 Common chemicals employed in home food production.
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Matter
1.2 CLASSIFICATIONS OF MATTER
Matter is anything that has mass and takes up space.
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Matter
1.2 CLASSIFICATIONS OF MATTER
• Atoms are the
building blocks of
matter.
• Each element is
made of a unique
kind of atom.
Note: Balls of different colors are used to represent
atoms of different elements. Attached balls represent
connections between atoms that are seen in nature.
These groups of atoms are called molecules.
• A compound is
made of two or
more different
kinds of elements.
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1.2 CLASSIFICATIONS OF MATTER
Methods of Classification
• Two principal ways of classifying matter are according to
physical state (gas, liquid, or solid) and according to
composition (element, compound, or mixture).
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1.2 CLASSIFICATIONS OF MATTER
States of Matter
 The three states of
matter are
1)
2)
3)
solid.
liquid.
gas.
 In this figure, those
states are ice,
liquid water, and
water vapor.
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1.2 CLASSIFICATIONS OF MATTER
Classification of Matter Based on Composition
 If you follow this
scheme, you
can determine
how to classify
any type of
matter.
 Homogeneous
mixture
 Heterogeneous
mixture
 Element
 Compound
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1.2 CLASSIFICATIONS OF MATTER
Classification of Matter—Substances
• A substance has distinct properties and a composition
that does not vary from sample to sample.
• The two types of substances are elements and
compounds.
 An element is a substance which can not be decomposed to
simpler substances.
 A compound is a substance which can be decomposed to
simpler substances.
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1.2 CLASSIFICATIONS OF MATTER
Compounds and Composition
• Compounds have a definite composition. That means
that the relative number of atoms of each element that
makes up the compound is the same in any sample.
• This is The Law of Constant Composition (or The
Law of Definite Proportions).
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1.2 CLASSIFICATIONS OF MATTER
Classification of Matter—Mixtures
• Mixtures exhibit the properties of the substances that
make them up.
• Mixtures can vary in composition throughout a sample
(heterogeneous) or can have the same composition
throughout the sample (homogeneous).
• Another name for a homogeneous mixture is solution.
Figure 1.8 Mixtures. (a) Many common materials,
including rocks, are heterogeneous mixtures. This
photograph of granite shows a heterogeneous
mixture of silicon dioxide and other metal oxides.
(b) Homogeneous mixtures are called solutions.
Many substances, including the blue solid shown
here [copper(II) sulfate], dissolve in water to form
solutions.
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1.3 PROPERTIES OF MATTER
Types of Properties
• Physical Properties can be observed without changing
a substance into another substance.
– Some examples include boiling point, density, mass, or volume.
• Chemical Properties can only be observed when a
substance is changed into another substance.
– Some examples include flammability, corrosiveness, or reactivity
with acid.
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1.3 PROPERTIES OF MATTER
Types of Properties
• Intensive Properties are independent of the amount of
the substance that is present.
– Examples include density, boiling point, or color.
• Extensive Properties depend upon the amount of the
substance present.
– Examples include mass, volume, or energy.
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1.3 PROPERTIES OF MATTER
Types of Changes
• Physical Changes are changes in matter that do not
change the composition of a substance.
– Examples include changes of state, temperature, and volume.
• Chemical Changes result in new substances.
– Examples include combustion, oxidation, and decomposition.
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1.3 PROPERTIES OF MATTER
Changes in State of Matter
 Converting between
the three states of
matter is a physical
change.
 When ice melts or
water evaporates,
there are still 2 H
atoms and 1 O atom
in each molecule.
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1.3 PROPERTIES OF MATTER
Chemical Reactions (Chemical Change)
In the course of a chemical reaction, the reacting
substances are converted to new substances.
Here, the elements hydrogen and oxygen become
water.
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1.3 PROPERTIES OF MATTER
Separating Mixtures
• Mixtures can be separated based on physical
properties of the components of the mixture.
• Some methods used are
filtration.
distillation.
chromatography.
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Filtration
1.3 PROPERTIES OF MATTER
• In filtration, solid substances are separated from liquids
and solutions.
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Distillation
1.3 PROPERTIES OF MATTER
• Distillation uses differences in the boiling points of
substances to separate a homogeneous mixture
into its components.
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1.3 PROPERTIES OF MATTER
Chromatography
• This technique separates substances on the basis
of differences in the ability of substances to adhere
to the solid surface, in this case, dyes to paper.
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1.4 UNITS OF MEASUREMENT
Numbers and Chemistry
• Numbers play a major role in chemistry. Many topics are
quantitative (have a numerical value).
• Concepts of numbers in science
Units of measurement
Quantities that are measured and calculated
Uncertainty in measurement
Significant figures
Dimensional analysis
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1.4 UNITS OF MEASUREMENT
THE SCIENTIFIC METHOD
Figure 1.16 The scientific method.
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1.4 UNITS OF MEASUREMENT
Units of Measurements—SI Units
• Système International d’Unités (“The International System
of Units”)
• A different base unit is used for each quantity.
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1.4 UNITS OF MEASUREMENT
Units of Measurement—Metric System
 The base units used in the metric system
–
–
–
–
–
–
Mass: gram (g)
Length: meter (m)
Time: second (s or sec)
Temperature: degrees Celsius (oC) or Kelvins (K)
Amount of a substance: mole (mol)
Volume: cubic centimeter (cc or cm3) or liter (l)
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1.4 UNITS OF MEASUREMENT
Units of Measurement—Metric System Prefixes
 Prefixes convert
the base units
into units that are
appropriate for
common usage
or appropriate
measure.
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1.4 UNITS OF MEASUREMENT
Mass and Length
• These are basic units we measure in science.
• Mass is a measure of the amount of material in an
object. SI uses the kilogram as the base unit. The
metric system uses the gram as the base unit.
• Length is a measure of distance. The meter is the
base unit.
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Temperature
1.4 UNITS OF MEASUREMENT
 In general usage,
temperature is
considered the “hotness
and coldness” of an
object that determines
the direction of heat flow.
 Heat flows spontaneously
from an object with a
higher temperature to an
object with a lower
temperature.
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Temperature
1.4 UNITS OF MEASUREMENT
• In scientific measurements, the Celsius and Kelvin scales
are most often used.
• The Celsius scale is based on the properties of water.
– 0 °C is the freezing point of water.
– 100 °C is the boiling point of water.
• The kelvin is the SI unit of temperature.
– It is based on the properties of gases.
– There are no negative Kelvin temperatures.
– The lowest possible temperature is called absolute zero (0 K).
• K = °C + 273.15
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Temperature
1.4 UNITS OF MEASUREMENT
• The Fahrenheit scale is not used in scientific
measurements, but you hear about it in weather
reports!
• The equations below allow for conversion
between the Fahrenheit and Celsius scales:
– °F = 9/5(°C) + 32
– °C = 5/9(°F − 32)
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Volume
1.4 UNITS OF MEASUREMENT
• Note that volume is not a base
unit for SI; it is derived from
length (m × m × m = m3).
• The most commonly used
metric units for volume are the
liter (L) and the milliliter (mL).
 A liter is a cube 1 decimeter (dm)
long on each side.
 A milliliter is a cube 1 centimeter
(cm) long on each side, also
called 1 cubic centimeter (cm ×
cm × cm = cm3).
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Density
1.4 UNITS OF MEASUREMENT
• Density is a physical property of a
substance.
• It has units that are derived from
the units for mass and volume.
• The most common units are g/mL
or g/cm3.
• Density (d) = mass (m) / volume (V)
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1.5 UNCERTAINTY IN MEASUREMENT
Numbers Encountered in Science
• Exact numbers are counted or given by definition. For
example, there are 12 eggs in 1 dozen.
• Inexact (or measured) numbers depend on how they
were determined. Scientific instruments have limitations.
Some balances measure to ±0.01 g; others measure to
±0.0001g.
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1.5 UNCERTAINTY IN MEASUREMENT
Uncertainty in Measurements
• Different measuring devices have different uses and
different degrees of accuracy.
• All measured numbers have some degree of inaccuracy.
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1.5 UNCERTAINTY IN MEASUREMENT
Accuracy versus Precision
• Accuracy refers to the proximity of a
measurement to the true value of a quantity.
• Precision refers to the proximity of several
measurements to each other.
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1.5 UNCERTAINTY IN MEASUREMENT
Significant Figures
• The term significant figures refers to digits that were
measured.
• When rounding calculated numbers, we pay attention to
significant figures so we do not overstate the accuracy
of our answers.
Figure 1.23 Uncertainty and
significant figures in a measurement.
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1.5 UNCERTAINTY IN MEASUREMENT
Significant Figures
1.
All nonzero digits are significant.
2.
Zeroes between two significant figures are themselves
significant.
1005 kg; 7.03 cm
1005 kg; 7.03 cm
3.
Zeroes at the beginning of a number are never
significant.
0.02 g; 0.0026 cm
4.
Zeroes at the end of a number are significant if a
decimal point is written in the number.
0.0200 g; 3.0 cm
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1.5 UNCERTAINTY IN MEASUREMENT
Significant Figures
• When addition or subtraction is performed, answers
are rounded to the least significant decimal place.
• When multiplication or division is performed, answers
are rounded to the number of digits that corresponds
to the least number of significant figures in any of
the numbers used in the calculation.
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1.5 UNCERTAINTY IN MEASUREMENT
Significant Figures
• Rounding off numbers: Look at the leftmost digit to be removed.
– If the leftmost digit removed is less than 5, the preceding number is left
unchanged.
• Rounding 7.248 to two significant figures gives 7.2.
– If the leftmost digit removed is 5 or greater, the preceding number is
increased by 1.
• Rounding 4.735 to three significant figures gives 4.74, and rounding 2.376 to
two significant figures gives 2.4.
• Calculation involving two or more steps.
– If you write answers for intermediate steps, retain at least one
nonsignificant digit for the intermediate answers.
• This procedure ensures that small errors from rounding at each step do not
combine to affect the final result.
– If you use a calculator, enter the numbers one after another and round
only the final answer.
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1.6 DIMENSIONAL ANALYSIS
Dimensional Analysis
• We use dimensional analysis to convert one quantity to
another.
• Most commonly, dimensional analysis utilizes conversion
factors (e.g., 1 in. = 2.54 cm).
1 in.
2.54 cm
or
2.54 cm
1 in.
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1.6 DIMENSIONAL ANALYSIS
Dimensional Analysis
• Use the form of the conversion factor that puts
the sought-for unit in the numerator:
Given unit ×
desired unit
given unit
= desired unit
Conversion factor
• For example, to convert 8.00 m to inches, convert m to
cm and convert cm to in.
100 cm
1 in.
8.00 m ×
= 315 in.
×
1m
2.54 cm
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Chapter 1. Homework
Exercises 1.6
1.13
1.19
1.29
1.42
1.48
1.84
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