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CHEMISTRY
The Central Science
9th Edition
Chapter 1
Introduction: Matter &
Measurement
David P. White
Prentice Hall © 2003
Chapter 1
The Study of Chemistry
Molecular Perspective of Chemistry
• Matter is anything that has mass and occupies
space.
• Matter ultimately consists of atoms.
• Atoms are nature’s building blocks.
• Compounds may consist of the same type of
atoms or different types of atoms.
Prentice Hall © 2003
Chapter 1
The Study of Chemistry
Why Study Chemistry?
• Chemistry is the study of the composition of
matter and the changes that matter undergoes.
• Five general types of chemistry: organic,
inorganic, biochemistry, analytical, and physical.
• CHEMISTRY STUDIES EVERYTHING!!
Prentice Hall © 2003
Chapter 1
Classification of Matter
Three States of Matter:
• Gas, liquid, or solid.
• Gases (vapors) have an indefinite shape, indefinite
volume, and can be compressed.
• Liquids have an indefinite shape, but a definite
volume. Liquids are not compressible.
• Solids are rigid, having a definite shape and
volume. They are not compressible.
Prentice Hall © 2003
Chapter 1
Classification of Matter
Substances, Elements and Compounds:
• Substance: matter having distinct properties and the same
composition from sample to sample. Substances can be
classified as elements or compounds.
• Element: simplest form of matter that has a unique set of
properties. Cannot be decomposed. Each element contains
a unique kind of atom. Ex.: H or C
• Compound: a substance containing two or more
elements chemically combined in a fixed proportion and
structure. Ex.: NaCl
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Chapter 1
Law of Constant
Composition (c. 1800)
• Also called the Law of Definite Proportions.
• A given compound always contains exactly
the same proportion of elements by mass
regardless of the source of the compound.
• Example: A molecule of pure water (H2O)
always is made up of two hydrogen atoms
and one oxygen atom.
Prentice Hall © 2003
Chapter 1
Classification of Matter
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Pure Substances and Mixtures
Mixtures: combinations of different substances.
Composition of mixtures can vary from sample to sample.
If matter is not uniform throughout, then it is a
heterogeneous mixture. Ex.: vegetable soup
If matter is uniform throughout, it is homogeneous.
Ex.: air.
Homogeneous mixtures are called solutions. Solutions
can be gaseous, liquid, or solid!
Prentice Hall © 2003
Chapter 1
Mixtures, Substances,
Compounds
• If homogeneous matter can be separated by
physical means, then the matter is a mixture.
• If homogeneous matter cannot be separated by
physical means, then the matter is a pure
substance.
• If a pure substance can be decomposed into
something else, then the substance is a compound.
Prentice Hall © 2003
Chapter 1
Classification of Matter
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Elements
If a pure substance cannot be decomposed into
something else, then the substance is an element.
Each element is given a unique chemical symbol (one or
two letters).
Elements are building blocks of matter.
The main elements in the human body: CHNOPS!
Prentice Hall © 2003
Chapter 1
Properties of Matter
Types of properties
Physical properties can be measured without changing the
identity and composition of a substance. Ex.: color,
density, m.p.
• Intensive properties do not depend on the amount of
substance. Ex.: m.p., b.p., density
• Extensive properties depend on the amount of substance
present. Ex.: mass, volume
Chemical properties describe how a substance reacts to
form other substances. Ex: flammability
Prentice Hall © 2003
Chapter 1
Changes of Matter
Physical and Chemical Changes
• When a substance undergoes a physical change, its
physical appearance changes, not its composition!
Ex. Changes of state (ice melting)
• When a substance changes its composition, it undergoes
a chemical change. Chemical changes = chemical
reactions
Ex.: solid iron + gaseous oxygen form solid iron oxide
Prentice Hall © 2003
Chapter 1
Properties of Matter
Physical and Chemical Changes
Prentice Hall © 2003
Chapter 1
Chemical Changes
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Four Clues to Chemical Changes
Transfer of energy
Change in color
Production of gas
Formation of a precipitate: solid that forms or settles
out from a liquid mixture.
But…even with a clue, you cannot be sure of a
chemical change! You need to test the composition of
the sample before and after to be sure!
Prentice Hall © 2003
Chapter 1
Properties of Matter
Separation of Mixtures
• Mixtures can be separated if their physical properties
are different.
• Separation is based on differences in physical
properties.
• Separation by filtration, distillation, chromatography,
etc.
Prentice Hall © 2003
Chapter 1
Properties of Matter
Separation of Mixtures
• Homogeneous liquid mixtures can be separated by
distillation.
• Distillation requires the different liquids to have
different boiling points.
• In essence, each component of the mixture is
boiled and collected.
• The lowest boiling fraction is collected first.
Prentice Hall © 2003
Chapter 1
Separation of Mixtures
Properties of Matter
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Separation of Mixtures
Chromatography separates mixtures that have different
abilities to adhere to solid surfaces.
The greater the affinity the component has for the surface
(paper) the slower it moves.
The greater affinity the component has for the liquid, the
faster it moves.
Chromatography can be used to separate the different
colors of inks in a pen.
Prentice Hall © 2003
Chapter 1
Units of Measurement
SI Units (Système International d’Unités)
• There are two types of units:
– fundamental (or base) units;
– derived units.
Prentice Hall © 2003
Chapter 1
Units of Measurement
Prentice Hall © 2003
Chapter 1
Units of Measurement
Prefixes in the Metric System
Prentice Hall © 2003
Chapter 1
Units of Measurement
Derived Units
• Derived units are obtained from base SI units.
• Example:
units of distance
Units of velocity =
units of time
meters
=
seconds
= m/s
Prentice Hall © 2003
Chapter 1
Units of Measurement
Temperature
There are three temperature scales:
• Kelvin Scale (Absolute Scale)
– Used in science.
– Same temperature increment as Celsius scale.
– Lowest temperature possible = absolute zero
– Absolute zero: 0 K = -273.15 oC.
Prentice Hall © 2003
Chapter 1
Units of Measurement
Temperature
• Celsius Scale
– Water freezes at 0 oC and boils at 100 oC.
– To convert: K = oC + 273.15.
• Fahrenheit Scale
freezes at 32 oF and boils at 212 oF.
– To convert:
_Water
5
¡C = (¡F - 32 )
9
Prentice Hall © 2003
9
¡F = (¡C ) + 32
5
Chapter 1
Units of Measurement
Temperature
Units of Measurement
Density
• Used to identify substances.
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mass
Density =
volume
Units: g/cm3 or g/mL
Density is an intensive property.
Density is temperature dependent. Why?
Water is different!
Prentice Hall © 2003
Chapter 1
Exact and Inexact
Numbers
• Two kinds of numbers are used in science.
• Exact numbers: values are known exactly;
values are infinitely precise. Ex: definitions
(12 inches = 1 foot), the number 1 in
conversion factors, counting numbers
• Inexact numbers: values have uncertainty.
Ex: all measurements (12.34 cm)
Prentice Hall © 2003
Chapter 1
Uncertainty in Measurement
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Uncertainty in Measurement
All scientific measures are subject to error.
These errors are reflected in the number of figures
reported for the measurement.
Precision and Accuracy
Measurements that are close to the “correct” value are
accurate.
Measurements that are close to each other are precise.
Prentice Hall © 2003
Chapter 1
Uncertainty in Measurement
Precision and Accuracy
Prentice Hall © 2003
Chapter 1
Uncertainty in Measurement
Significant Figures
• Number of digits reported in a measurement reflect
the accuracy of the measurement and the precision
of the measuring device.
• Significant figures: all the figures known with
certainty plus one extra figure.
Prentice Hall © 2003
Chapter 1
Uncertainty in Measurement
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Significant Figures Rules
Non-zero numbers are always significant.
Zeros between non-zero numbers are always significant.
Zeros before the first non-zero digit are not significant.
(Example: 0.0003 has one significant figure.)
Zeros at the end of the number after a decimal point are
significant.
Zeros at the end of a number with no decimal point are
ambiguous (e.g. 10,300 g). Use scientific notation or a
decimal to indicate number of significant figures.
Prentice Hall © 2003
Chapter 1
Uncertainty in Measurement
Significant Figures
• Multiplication & Division: report answer to the
smallest number of significant figures in the
calculation.
• Addition & Subtraction: report answer to the
smallest number of decimal places in the
calculation.
Prentice Hall © 2003
Chapter 1