Name: _____________________________________________________ Date: __________________ Period: ______
Chapter 3: Matter and Change
3.1 Matter
Main Idea: Atoms are the basic building blocks of all matter.
Matter: anything that has volume and mass.
 All matter is made of substances called elements.
Element: substance that cannot be broken down into simpler substances by physical or chemical means.
Elements are made up of atoms.
Atom: the smallest particle of an element that retains all the properties of that element.
Structure of an Atom
“Everything that is made of atoms (matter) is mostly empty space.” - Bill Nye Video
Nucleus: center of the atom (made of protons and neutrons)
Proton: tiny particle that has mass and a positive electric charge.
Neutron: tiny particle with about the same mass as a proton, but it has no
electrical charge.
Surrounding the nucleus of an atom are electrons, smaller particles that are in constant motion.
Electron: has little mass, but it has a negative electric charge that is exactly the same magnitude as the
positive charge of a proton.
The periodic table of the elements is arranged so that a great deal of
information about all of the known elements is provided in a small space.

Each element is identified by a one-, two-, or three-letter
abbreviation known as a chemical symbol (first letter only capital)

All elements are classified and arranged according to their
chemical properties in the periodic table of the elements.
Atomic Number: number of protons in an atom’s nucleus.
Mass Number: sum of the protons and the neutrons in an atom’s nucleus (whole #).
 All atoms of an element have the same number of protons.
However, the number of neutrons of an element’s atoms can vary.
Isotopes: atoms of the same element that have different mass numbers are called isotopes.
Atomic mass: average of the mass numbers of the isotopes of an element (decimal #).
Radioactivity
Radioactive decay: spontaneous process through which unstable nuclei emit radiation.
 In the process of radioactive decay, a nucleus can lose protons and neutrons, change a proton to a
neutron, or change a neutron to a proton.
 Because the number of protons in a nucleus identifies an element, decay can change the element.
Electrons & Energy Levels

Although the exact position of an electron cannot
be determined, scientists have discovered that
electrons occupy areas called energy levels.

Electrons are distributed over one or more energy
levels in a predictable pattern.

Each energy level can hold only a limited number
of electrons.
Electrons occupy one energy level in hydrogen, two energy
levels in oxygen, and three energy levels in aluminum.
Valence Electrons & Chemical Behavior
Valence Electrons: electrons in the outermost energy level; they determine the chemical behavior of elements.
 Elements with the same number of valence electrons have similar chemical properties.
 Elements that have full outermost energy levels are highly unreactive, which
means that they do not combine easily with other elements. This is also true (to a
lesser to degree) for elements with 8 valence electrons.
 The inert nature of argon makes it an ideal gas to use inside an incandescent light
bulb because it does not react with the extremely hot filament.
Ions
Ion: atom that gains or loses one or more electrons from its outermost energy level; has a net electric charge.
 In general, an atom in which the outermost energy level is less than half-full (or has fewer than four
valence electrons) tends to lose its valence electrons and forms a positively charged ion.
 An atom in which the outermost energy level is more than half-full (or has more than four valence
electrons) tends to gain electrons to fill its outermost energy level and forms a negatively charged ion.
Electronegativity: tendency of an element or compound to attract electrons towards itself.
The higher the electronegativity number, the more it attracts electrons towards it.
 The two most abundant elements in the universe are hydrogen and helium. However, the two most
abundant elements in Earth’s crust are oxygen and silicon.
3.2 Combining Matter
Main Idea: Atoms combine through electric forces, forming molecules and compounds.
Compound: substance composed of atoms of two or more different elements that are chemically combined.
 Compounds have different properties from the elements of which they are composed (e. g. H2O).
 Compounds are represented by chemical formulas that include the symbol for each element followed by a
subscript showing the number of atoms of that element in the compound (no subscript if just 1).
 A state of stability is achieved by some elements by forming chemical bonds.
Types of Chemical Bonds
Chemical Bond: force that holds together the elements in a compound.
Covalent Bond: attraction that holds together 2 atoms with a shared pair of electrons.
 In this example (H2), the nucleus of each atom has one proton with a positive charge. The
two positively charged protons attract the two negatively charged electrons.
Molecule: composed of two or more atoms held together by covalent bonds.
 A compound comprised of molecules is called a molecular compound.
 Polar Molecules (right): molecules held
together by covalent bonds in which the electrons
are not shared equally, resulting in the electrons spending more
time near one atom than another; it will thus have a slightly positive
end and a slightly negative end.
Ionic bond: attractive force between two ions
of opposite charge.
 Compounds formed by ionic bonds are called ionic compounds.
 A sodium atom tends to lose a single valence electron, and a chlorine atom tends to
gain a single valence electron.
Metallic bond: the positive ions of a metal are held together by
the attraction to the negative electrons moving among them.

Metallic bonds allow metals to conduct electricity because some of the electrons move
freely throughout the entire metal.

When a force is applied to a metal, some of the electrons are pushed aside. This allows the metal ions to
move past each other, thus deforming or changing the shape of the metal.
 Atoms gain stability by sharing, gaining, or losing electrons to form ions and molecules. The properties of metals
can be explained by metallic bonds.
Chemical Reaction: change of one or more compounds into other compounds.
o
Chemical reactions are described by chemical equations.
o
Water is formed by the chemical reaction between hydrogen gas (H2) and oxygen gas (O2).
o
You must balance the equation by showing an equal number of atoms for each element on each side of the
equation. Therefore, the same amount of matter is present both before and after the reaction.
Mixture: a combination of two or more components that retain their identities.
Heterogeneous mixture: when a mixture’s components are easily recognizable
Homogeneous mixture (solution): when the component particles cannot be distinguished, even though they still retain
their original properties. A solution can be liquid, gaseous, or solid.
Acid: solution containing a substance that produces hydrogen ions
(H+) in water. The pH scale is based on the amount of hydrogen ions
in a solution.
Base: solution producing hydroxide ions (OH–) in water.
3.3 States of Matter
Main Idea: All matter on Earth and in the universe occurs in the form of a solid, liquid, gas, or plasma.
Solids: substances with densely packed particles, which can be ions, atoms, or molecules.
 Most solids are crystalline structures because the particles of a solid are arranged in regular geometric
patterns, giving solids definite shape and volume.
 Glass is a solid that consists of densely packed atoms arranged randomly.
 An increase in temperature increases the thermal vibrations of atoms in a solid.
 When thermal vibrations become vigorous enough to break the forces holding the solid together, the particles
can slide past each other, and the substance becomes liquid.
Liquids: take the shape of the container they are placed in, but they do have a definite volume.
 Some vibrating particles can gain sufficient thermal energy to escape a liquid.
Evaporation: process of changing from a liquid to a gas at temperatures below the boiling point.
Gases: have no definite shape and no definite volume unless restrained by a container or a force such as gravity.
Plasmas: At extreme temperatures, the collisions between particles in matter are so violent that electrons are
knocked away from atoms, resulting in hot, highly ionized, electrically conducting gases.
Changes of State
Melt: when solids absorb enough thermal energy to cause their orderly internal crystalline arrangement to break
down. This happens at the melting point.
Freeze: when liquids are cooled to the freezing point they solidify and release thermal energy.
 Freezing Point is the same temperature as the melting point.
Vaporization: when a liquid is heated to the boiling point and absorbs enough thermal energy to become a gas.
Condensation: when a gas is cooled to the boiling point, it releases thermal energy and becomes a liquid.
Sublimation: the slow change of state from a solid to a gas without an intermediate liquid state
Conservation of Energy
Law of Conservation of Matter: the fundamental fact that matter cannot be created or destroyed.
Law of Conservation of Energy (First Law of Thermodynamics): energy cannot be created or destroyed.
 Like matter, energy cannot be created or destroyed, but it can be changed from one form to another.