Unit E
Chapter 14 Composition of Matter
Lesson 1: What are the building blocks of matter?
Atom- the basic building block of matter
They consist of a nucleus surrounded by moving
electrons.
The nucleus contains protons and neutrons.
Protons are positively charged.
Neutrons are uncharged.
Electrons are negatively charged particles that
reside in orbitals around the nucleus.
Atomic Number- the number of protons in an atom.
For example, oxygen’s atomic number is 8- it has
8 protons in its nucleus
Neutral atoms have the same number of protons
and electrons.
Ion- is an atom that has more or less electrons than
protons.
They can have a positive or negative charge.
Positive ions have more protons than electrons, for
example sodium, 11 protons and 10 electrons.
Negative ions have more electrons than protons,
for example, fluoride has 9 protons and 10
electrons.
Isotopes- atoms with the same number of protons
but a different number of neutrons. For example,
hydrogen has three isotopes, all with 1 proton but a
different number of neutrons.
Carbon-14 is another example of an isotope. It has
14 particles in the nucleus- 6 protons and 8
neutrons.
Isotopes with unstable nuclei are said to be
radioactive.
Their nuclei become stable by giving off particles
and energy called radiation.
Three types of radiation: alpha, beta, gamma
Element- a substance that cannot be broken down
into other substances. An atom is the smallest unit
of an element. For example, hydrogen, H, nitrogen,
N, and oxygen, O.
All atoms of an element contain the same number
of protons.
Scientists classify elements based on their
properties.
One way is metals, nonmetals, and semimetals.
Another way is state of matter: solid, liquid, or
gas.
1869 Dmitri Mendeleyev arranged elements in the
first Periodic Table.
Was able to make predictions about elements not
yet discovered.
 Today’s table arranges the elements by their
atomic number.
There are more than 114 elements.
Lesson 2: Compounds
A pure substance always has the same composition
and properties. For example, carbon dioxide, CO2
Two types: elements and compounds
Compound- a pure substance made up of two or
more elements that are chemically combined
For example: carbon dioxide is made up of one atom
of carbon C and two atoms of oxygen O = CO2
Elements that combine to form compounds usually
do not keep their original properties.
The formation of a compound involves a chemical
change.
Chemical bond – a force of attraction between
atoms or ions
Two types of bonds: covalent and ionic
Covalent Bond- formed when two atoms share their
outermost electrons. For example, methane, CH4
Molecule- a group of two or more atoms held
together by covalent bonds
Ionic Bond- formed when one or more electrons are
removed form one atom and attached to another
atom. For example, table salt, NaCl which is one atom
of sodium and one atom of chlorine.
Carbon forms more compounds than any other
element except hydrogen
Hydrocarbons- hydrogen and carbonmethane,CH4 and propane, C3H8
Oil, natural gas, and other fuels are hydrocarbons
Polymers – long chains of carbon atoms- human
made plastics are polymers
Carbohydrates are made of carbon, hydrogen and
oxygen. Sugar, starch an cellulose
∴ Carbons are a part of everyday life!
(∴ = thus)
Lesson 3: Mixtures
A mixture is made up of two or more pure
substances that are not chemically combined. Each
substance keeps its original properties. For example,
vegetable soup
Most matter is in the form of mixtures.
Two types of mixtures: heterogeneous and
homogeneous
heterogeneous- mixture is unevenly mixed. For
example, vegetable soup, trail mix, fruit salad, soil,
and concrete.
homogeneous – mixture that is evenly mixed. It
appears to be made up of only one kind of matter.
For example, air, sea water, a bridge made of steel.
Solutions are a type of homogeneous mixture
that are evenly mixed at the molecular level.
They have two parts: solute and solvent
Solute is the one present in the lesser amount
Solvent has the greater amount- water is often
called the universal solvent because of its ability
to dissolve so many other substances.
For example, sugar water= sugar (solute) + water
(solvent)
The rate of dissolving is affected by stirring, the
surface area of the solute, and the temperature
of the solvent.
Heat or stirring will dissolve a solute more
quickly.
Alloys- are solutions of one or more metals and other
solids
Lesson 4: Acids and Bases
An acid is a substance that tastes sour and turns blue
litmus paper red.
 Acids add hydrogen ions (H+)
For example, lemon juice, vinegar, hydrochloric acid
that digests food in your stomach, soft drinks, tomato
juice.
A base is a substance that feels slippery, tastes bitter
and turns red litmus paper blue.
 Bases add hydroxide (OH-)
For example, soaps, baking soda, drain cleaners,
ammonia, fertilizers, cements.
pH scale- is the system to measure the strength of an
acid or base when dissolved in water.
 Typically it runs from 0 to 14
 Acids are 0 to 7
 Bases are from 7 to 14
 Pure water is neutral- neither acidic or basic
 pH means “potential of hydrogen”
Uses of acids and bases
Acids
 produce fertilizers, detergents, dyes, drugs and
explosives
 Citrus fruits and juices and soft drinks contain
weak acids
Bases
 Make plastics, soaps, fertilizers, paper
Acid Rain is precipitation (rain, sleet, hail, snow) that
contains dissolved carbon dioxide and has a pH of 3.5
or lower. (normal rain has a pH of 5.5)
 It is caused by burning fossil fuels, such as coal,
oil, and gasoline.
 It harms the environment by lowering the pH of
soil and water, damaging trees, killing fish, and
eroding buildings.