Introductory Chemistry: Concepts & Connections Introductory Chemistry: Concepts & Connections 4 th Edition by Charles H. Corwin Matter and Energy Christopher.

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 6

States of Matter Summary

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 11

Summary of Changes of State

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 24

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.

Chapter 4 43

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.