Summary of chemistry
Matter can exist in one of three main states: solid, liquid, or gas.
Solid matter is composed of tightly packed particles. A solid will retain its
shape; the particles are not free to move around. Liquid matter is made of
more loosely packed particles.
Matter can exist in one of three main states: solid, liquid, or gas.
Solid matter is composed of tightly packed particles. A solid will retain
its shape; the particles are not free to move around.
Liquid matter is made of more loosely packed particles. It will take the
shape of its container. Particles can move about within a liquid, but
they are packed densely enough that volume is maintained.
Gaseous matter is composed of particles packed so loosely that it has
neither a defined shape nor a defined volume. A gas can be
compressed.
Solid a substance that retains its size and shape without a container; a
substance whose molecules cannot move freely except to vibrate.
Gas a substance that can only be contained if it is fully surrounded by
a container (or held together by gravitational pull); a substance whose
molecules have negligible intermolecular interactions and can move
freely.
Liquid a substance that flows and keeps no definite shape because its
molecules are loosely packed and constantly moving. It takes the
shape of its container but maintains constant volume.
What are some chemical properties that can be used to describe matter?
Density is: the amount of matter in a given space. Some of
these properties are: density, melting point, boiling point, and what it
reacts with.
Physical property - a characteristic of a pure substance that can be
observed without changing it into another substance
Chemical properties: a characteristic of a pure substance that describes
its ability to change into a different substance with new properties
Elements are pure substances made up of only one type of atom. They
cannot be broken down into a simpler substance
Each element has its own atomic structure and a unique set of physical
and chemical properties that identify it
The smallest particle of each element is the atom
Compounds – a pure substance composed of two or more elements
chemically combined, in a set ratio - smallest piece of a compound is called
a molecule.
Most elements in nature are combined with other elements, most
substances we use everyday are made of compounds.
Chemical formula - Compounds mix according to certain ratios
Compounds can be chemically broken down into the individual elements
that form them
Two Kinds of Mixtures
a) Heterogeneous mixtures have particles big enough to see, they are not
evenly mixed and some particles are big enough to separate out.
b) Homogeneous mixtures look the same throughout, they are evenly
mixed and do not separate on their own.
Classification of matter and separation
• Pure Substance that cannot be broken down into any other
substances by chemical or physical means
• Element
• composed of identical atoms
EX: copper wire, aluminum foil]
• Compound
– composed of 2 or more elements in a fixed ratio
– properties differ from those of individual elements
– Chemical bonds hold the elements together
Definite Composition
A given compound always contains the same, fixed ratio of elements.
Two different compounds,
each has a definite composition
Molecules
• Groups of two or more atoms bound by chemical bonds
• Can be two of the same element
Classification of Matter
This well-known molecule is a compound
because it contains more than one element.
Ordinary solid salt is a compound but not a molecule.
It is built from interpenetrating lattices of sodium and
chloride ions that extend indefinitely.
A molecule but not a compound
Ozone, O3, is not a compound because it contains only a single element.
Mixtures
Variable combination of two or more pure substances. Each keep individual
properties
Heterogeneous – Can see different parts (different)
Homogeneous- Evenly Mixed cannot see different parts. (Same)
Extensive Properties: depend on the amount of the substance present.
Examples: mass, volume, or energy.
Intensive Properties: independent of the amount of the substance that is
present.
Examples: density, boiling point, and color.
History of atoms
Democritus
Proposed an Atomic Theory
• states that all atoms are small, hard, indivisible and indestructible
particles made of a single material formed into different shapes and
sizes.
• Aristotle did not support his atomic theory
Antoine Lavoisier
“Father of Modern Chemistry”
first person to generate a list of thirty-three elements
Discovered/proposed that combustion occurs when oxygen combines
with other elements
Discovered/proposed the Law of Conservation of Mass (or Matter)
which states, in a chemical reaction, matter is neither created nor
destroyed
John Dalton
proposed an Atomic Theory
All substances are made of atoms
o Atoms of the same element are exactly alike, and atoms of
different elements are different
o Atoms join with other atoms to make new substances
J.J. Thomson
Proved that an atom can be divided into smaller parts
discovered corpuscles, which were later called electrons
Stated that the atom is neutral
proposed the Plum Pudding Model
consist of positively charged material with negatively charged particles
(electrons)
Ernest Rutherford
Father of Nuclear Physics
The protons are surrounded by negatively charged electrons, but
most of the atom is actually empty space
Was a student of J.J. Thomson
Did extensive work on radioactivity (alpha & beta particles,
gamma rays/waves)
Niels Bohr
proposed the Bohr Model - suggests that electrons travel around the
nucleus of an atom in orbits or definite paths
the electrons can jump from a path in one level to a path in another level
(depending on their energy)
Erwin Schrodinger
he further explained the nature of electrons in an atom by stating that the
exact location of an electron cannot be stated; therefore, it is more accurate
to view the electrons in regions called electron clouds → places where the
electrons are likely to be found
James Chadwick
discovery of the neutron
Worked with Ernest Rutherford
Ionic compounds are composed of metals and non-metals.
Molecular compounds are composed of non-metals.
Acids have one or more hydrogens bound to an anion. The hydrogens
dissociate from the anion when placed in water.
Ionic Compounds An ionic compound is composed of a cation and an
anion. Metals lose electrons to form cations. Non-metals gain electrons to
form anions.
Cation - a positively charged ion, i.e. one that would be attracted to the
cathode in electrolysis.
Anions: There are two classes of anions, single atom (monoatomic) non-
metals and polyatomic anions.
Monoatomic anions are formed from group 4A through 7A elements.
Polyatomic anions are of two general types, the oxoanions and the
“others”. The ones you need to know are included in the table at the end of
this handout. You need to know their formula, their charge, and their name.
Molecular Compounds These compounds are composed of non-metals.
The elements are held together by covalent bonds. You will be responsible
for naming binary compounds, compounds composed of two elements.
