Transcript Matter and Energy

Introductory Chemistry:
Concepts & Connections
4th Edition by Charles H. Corwin
Chapter 4
Matter and
Energy
Christopher G. Hamaker, Illinois State University, Normal IL
© 2005, Prentice Hall
Matter
• Matter is any substance that has mass and
occupies volume.
• Matter exists in one of three physical state:
– Solid
– Liquid
– Gas
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Gaseous State
• In a gas, the particles of matter are far apart and
uniformly distributed throughout the container.
• Gases have an indefinite shape and assume the
shape of their container.
• Gases can be compressed and have an indefinite
volume.
• Gases have the most energy of the three states of
matter.
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Liquid State
• In a liquid, the particles of matter are loosely
packed and are free to move past one another.
• Liquids have an indefinite shape and assume the
shape of their container.
• Liquids cannot be compressed and have a definite
volume.
• Liquids have less energy than gases but more
energy than solids.
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Solid State
• In a solid, the particles of matter are tightly
packed together.
• Solids have a definite, fixed shape.
• Solids cannot be compressed and have a definite
volume.
• Solids have the least energy of the three states of
matter.
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States of Matter Summary
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Changes of State
• Most substances can exist as either a solid, liquid,
or gas.
• Water exists as a solid below 0°C; as a liquid
between 0°C and 100°C; and as a gas above
100°C.
• A substance can change physical states as the
temperature changes.
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Solid/Liquid Phase Changes
• When a solid changes to a liquid, the phase
change is called melting.
• A substance melts as the temperature increases.
• When a liquid changes to a solid, the phase
change is called freezing.
• A substance freezes as the temperature decreases.
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Liquid/Gas Phase Changes
• When a liquid changes to a gas, the phase change
is called vaporization.
• A substance vaporizes as the temperature
increases.
• When a gas changes to a liquid, the phase change
is called condensation.
• A substance condenses as the temperature
decreases.
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Solid/Gas Phase Changes
• When a solid changes directly to a gas, the phase
change is called sublimation.
• A substance sublimes as the temperature
increases.
• When a gas changes directly to a solid, the phase
change is called deposition.
• A substance undergoes deposition as the
temperature decreases.
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Summary of Changes of State
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Classifications of Matter
• Matter can be divided into two classes:
– Mixtures
– Pure Substances
• Mixtures are composed of more than one
substance and can be physically separated into its
component substances.
• Pure substances are composed of only one
substance and cannot be physically separated.
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Mixtures
• There are two types of mixtures:
– Homogeneous Mixtures
– Heterogeneous Mixtures
• Homogeneous mixtures have uniform properties
throughout
– Saltwater is a homogeneous mixture
• Heterogeneous mixtures do not have uniform
properties throughout
– Sand and water is a heterogeneous mixture
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Pure Substances
• There are two types of pure substances:
– Compounds
– Elements
• Compounds can be chemically separated into
individual elements.
– Water is a compound that can be separated into
hydrogen and oxygen.
• An element cannot be broken down further by
chemical reactions.
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Occurrence of the Elements
• There are over 100 elements that occur in nature.
81 of those elements are stable.
• Only 10 elements account for 95% of the mass of
the Earth’s crust:
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Elements in the Human Body
• Oxygen is the most common element in both the
Earth’s crust and in the Human body.
• While silicon is the second-most abundant
element in the crust, carbon is the second most
abundant in the body.
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Names of the Elements
• Each element has a unique name.
• Names have several origins:
– Hydrogen is derived from Greek
– Carbon is derived from Latin
– Scandium is named for Scandinavia
– Nobelium is named for Alfred Nobel.
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Element Symbols
• Each element is abbreviated using a chemical
symbol.
• The symbols are 1 or 2 letters long.
• Most of the time, the symbol is derived from the
name of the element.
– C is the symbol for carbon
– Cd is the symbol for cadmium
• When a symbol has a two letter symbol, the first
is capitalized and the second is lower case.
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Other Element Symbols
• For some elements, the chemical symbol is
derived from the original Latin name.
Gold – Au
Sodium – Na
Silver – Ag
Antimony – Sb
Copper – Cu
Tin – Sn
Mercury – Hg
Iron – Fe
Potassium – K
Tungsten – W
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Types of Elements
• Elements can be divided into three classes:
– Metals
– Nonmetals
– Semimetals or metalloids
• Semimetals have properties midway
between those of metals and nonmetals
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Properties of Metals
• Metals are typically solids with high melting
points and high densities and have a bright,
metallic luster.
• Metals are good conductors of heat and electricity.
• Metals can be hammered into thin sheets and are
said to be malleable.
• Metals can be drawn into fine wires and are said
to be ductile.
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Properties of Nonmetals
• Nonmetals typically have low melting points and
low densities and have a dull appearance.
• Nonmetals are poor conductors of heat and
electricity.
• Nonmetals are not malleable or ductile and crush
into a powder when hammered.
• 11 nonmetals occur naturally in the gaseous state.
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Periodic Table of the Elements
• Each element is assigned a number to identify it.
It is called the atomic number.
• Hydrogen is 1, Helium is 2, up to Uranium which
is 92.
• The elements are arranged by atomic number on
the periodic table.
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The Periodic Table
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Metals, Nonmetals, and Semimetals
• Metals are on the left side of the periodic table,
nonmetals are on the right side, and the
semimetals are in between.
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Physical States of the Elements
• Shown are the physical states of the elements at
25°C on the periodic table.
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Law of Definite Composition
• The law of definite composition states that
“Compounds always contain the same elements in
a constant proportion by mass”.
• Sodium chloride is always 39.3% sodium and
60.7% chlorine by mass, no matter what its
source.
• Water is always 11.2% hydrogen and 88.8%
oxygen by mass.
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Chemical Formulas
• A particle composed of two or more nonmetal
atoms is a molecule.
• A chemical formula expresses
the number and types of atoms
in a molecule.
• The chemical formula of
sulfuric acid is H2SO4.
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Writing Chemical Formulas
• The number of each type of atom in a molecule is
indicated with a subscript in a chemical formula.
• If there is only one atom of a certain type, no ‘1’
us used.
• A molecule of the vitamin niacin has 6 carbon
atoms, 6 hydrogen atoms, 2 nitrogen atoms, and
1 oxygen atom. What is the chemical formula?
C6H6N2O
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Interpreting Chemical Formulas
• Some chemical formulas use parenthesis to clarify
atomic composition.
• Antifreeze has chemical formula C2H4(OH)2.
There are 2 carbon atoms, 4 hydrogen atoms, and
2 OH units, giving a total of 6 hydrogen atoms
and 2 oxygen atoms.
• Antifreeze has a total of 10 atoms.
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Physical & Chemical Properties
• A physical property is a characteristic of a pure
substance that we can observe without changing
its composition.
• Physical properties include appearance, melting
and boiling point, density, conductivity, and
physical state
• A chemical property describes the chemical
reactions of a pure substance.
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Chemical & Physical Changes
• A physical change is a change where the
chemical composition of the substance is not
changed.
• These include changes in physical state or shape
of a pure substance.
• A chemical change is a chemical reaction.
• The composition of the substances changes during
a chemical change.
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Evidence of a Chemical Change
• Gas release (bubbles).
• Light or release of heat energy.
• Formation of a precipitate.
• A permanent color change.
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Conservation of Mass
• Antoine Lavoisier found that the mass of
substances before a chemical change was always
equal to the mass of substances after a chemical
change.
• This is the law of conservation of mass.
• Matter is not created or destroyed in physical or
chemical processes.
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Conservation of Mass Continued
• If 1.0 grams of hydrogen combine with 8.0 grams
of oxygen, 9.0 grams of water is produced.
• Consequently, 3.0 grams of hydrogen combines
with 24.0 grams of oxygen to produce 27.0 grams
of water.
• If 50.0 grams of water decomposes to produce
45.0 grams of oxygen, how many grams of
hydrogen are produced?
50.0 g water – 45.0 g oxygen = 5.0 g hydrogen
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Potential and Kinetic Energy
• Potential energy, PE, is stored energy; it results
from position or composition.
• Kinetic energy, KE, is the energy matter has as a
result of motion.
• Energy can be converted between the two types.
• A boulder at the top of the hill has potential
energy; if you push it down the hill, the potential
energy is converted to kinetic energy.
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KE, Temperature, & State
• All substances have kinetic energy no matter what
physical state they are in.
• Solids have the lowest kinetic energy, and gases
have the greatest kinetic energy.
• As you increase the temperature of a substance, its
kinetic energy increases.
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Conservation of Energy
• Just like matter, energy cannot be created or
destroyed but it can converted from one form to
another.
• This is the law of conservation of energy.
• There are six forms of energy: heat, light,
electrical, mechanical, chemical, and nuclear.
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Energy and Chemical Change
• In a chemical change, energy is transformed from
one form to another. For example:
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Law of Conservation of
Mass and Energy
• Mass and energy are related by Einstein’s theory
of relativity, E = mc2.
• Mass and energy can be interchanged.
• The law of conservation of mass and energy
states that the total mass and energy of the
universe is constant.
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Conclusions
• Matter exists in three physical states:
– Solid
– Liquid
– Gas
• Substances can be converted between the three
states.
• Substances can be mixtures or pure substances.
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Conclusions Continued
• Pure substances can be either compounds or
elements.
• The elements are arranged in the periodic table.
• Each element has a name and a 1 or 2 letter
symbol.
• Elements are classified as either metals,
nonmetals, or semimetals.
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Conclusions Continued
• A physical change is a change in physical state or
shape.
• A chemical change is a change in the chemical
composition of a substance.
• Both mass and energy are conserved in chemical
and physical changes.
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