Introductory Chemistry:Introductory Chemistry:Concepts & ConnectionsConcepts & Connections
4th Edition by Charles H. Corwin
Matter and Matter and EnergyEnergy
Christopher G. Hamaker, Illinois State University, Normal IL© 2005, Prentice Hall
Chapter 4
Chapter 4 2
Matter
• Matter is any substance that has mass and occupies volume.
• Matter exists in one of three physical state:
– Solid
– Liquid
– Gas
Chapter 4 3
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.
Chapter 4 4
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.
Chapter 4 5
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.
Chapter 4 7
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.
Chapter 4 8
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.
Chapter 4 9
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.
Chapter 4 10
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.
Chapter 4 12
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.
Chapter 4 13
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
Chapter 4 14
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.
Chapter 4 15
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:
Chapter 4 16
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.
Chapter 4 17
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.
Chapter 4 18
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.
Chapter 4 19
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
Chapter 4 20
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
Chapter 4 21
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.
Chapter 4 22
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.
Chapter 4 23
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.
Chapter 4 25
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.
Chapter 4 26
Physical States of the Elements• Shown are the physical states of the elements at
25°C on the periodic table.
Chapter 4 27
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.
Chapter 4 28
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.
Chapter 4 29
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
Chapter 4 30
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.
Chapter 4 31
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.
Chapter 4 32
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.
Chapter 4 33
Evidence of a Chemical Change• Gas release (bubbles).
• Light or release of heat energy.
• Formation of a precipitate.
• A permanent color change.
Chapter 4 34
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.
Chapter 4 35
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
Chapter 4 36
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.
Chapter 4 37
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.
Chapter 4 38
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.
Chapter 4 39
Energy and Chemical Change• In a chemical change, energy is transformed from
one form to another. For example:
Chapter 4 40
Law of Conservation ofMass 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.
Chapter 4 41
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.
Chapter 4 42
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.