Chem 1 Unit 1 Review
Content Summary:
Kinetic Molecular Theory (KMT):
1. All matter is made of particles.
2. Particles are in constant, rapid, random motion, moving in straight lines in all directions until they
collide with other particles.
3. The average kinetic energy of the particles is directly proportional to the absolute temperature.
4. Solids, liquids, and gases differ in the freedom of motion of their particles and the extent to which
the particles interact.
Phases of Matter:
Phase
Shape
Volume
Flow
Solid
Definite
Definite
No
Liquid
Indefinite
Definite
Yes
Gas
Indefinite
Indefinite
Yes
Compressibility Particles
 Have a high force of attraction
 Vibrate but do not exchange
No
places with other particles
 Are packed closely together (see
water as an exception!)
 Have a lower force of attraction
than solids
No
 Can change places with other
particles but are still held
together
 Have no / little force of attraction
 Move in random directions
Yes
without much interaction with
other particles
 Are far apart from each other
Change of phase:
In exothermic reactions, heat
energy leaves a substance. In
enough energy is removed,
the attraction between
particles may cause them to
stick together.
In endothermic reactions, a
substance gains heat energy.
If enough energy is absorbed,
the attraction between
particles may be broken.
Types of matter:
1
2
3
1. Is the matter made of only one kind of chemical substance (element, compound, etc.)?
YES: Pure substance
NO: Mixture
2. Is the chemical substance made of only one kind of atom?
YES: Element
NO: Compound
3. Is the matter made of multiple substances that are, on average, evenly mixed throughout the
sample?
YES: homogenous mixture
NO: heterogeneous mixture
Physical and Chemical Properties:
Physical changes involve a change of state or appearance, but the chemical composition does not
change. Examples include shredding paper or melting ice.
Physical properties include: density, color, boiling point, etc.
Chemical changes involve a change in chemical composition (chemical reaction) by rearranging bonds
between atoms.
Chemical properties include: ability to react with other substances, heat of
combustion (energy released in burning), etc.
In the image to the right:
Water (H2O) is changing from a liquid to a gas – a physical change.
The boiling point is 100 °C – a physical property.
The methane (CH4) is combusting with oxygen gas (O2) to produce water
(H2O) and carbon dioxide (CO2) – a chemical change.
The heat of combustion for methane is 890 kJ/mol – a chemical property.
Structure of atoms:
Electric charge
Proton (p+)
+1
Neutron (n0)
0
Electron (e-)
-1
*masses are not exact
Relative mass *
1
1
0
Location
Nucleus
Nucleus
Orbitals
# determines atom’s
Element
Isotope
Ionization
Neutral atoms:
A-Z notation shows the atomic symbol (one or two letters; the first letter capitalized) with the mass
number as a superscript on the left side and the atomic number as a subscript on the right side.
Example for Beryllium:
9
4
Be
This Beryllium atom has:
o 4 protons
o 5 neutrons
o 4 electrons
Isotopes:
Atoms of an element must all have the same
number of protons. However, they may have
different numbers of neutrons. Atoms of the same
element with different number of neutrons are
called isotopes. Some isotopes may be common
and other isotopes very rare.
The average atomic mass of an element is
determined by taking into account its mass
(protons plus neutrons) and how common it is in
the sample.
Ions:
An ion is an atom* with an overall charge. All neutral atoms have the same number of protons as
electrons - the number of negative charges equals the number of positive charges. However, in
chemical reactions atoms can gain or lose
electrons.
*(or group of atoms, but don't worry about that)
Having more electrons than protons results in a
negative ion, or anion.
Having fewer electrons than protons results in a
positive ion, or cation. Sodium forms a cation.
Electron arrangement:
 The first energy level can hold 2 electrons.
 The second and third energy levels can hold 8 electrons each.
 The electrons in the outermost energy level of an atom are called valence electrons.
Periodic Table:
The elements are arranged according to two rules:
1) The elements are in sequential order by atomic number (number of protons), starting with 1
(Hydrogen) in the upper left hand corner.
2) The elements are divided so that they form columns (known as groups) that reflect their
arrangement of electrons. Elements in the same group will all have the same number of valence
electrons (see below). Elements in a group will have similar chemical properties.
Lewis Dot Diagrams:
1. Find the number of valence electrons
2. Write the element symbol
3. Draw one dot to represent each valence
electron around the four sides of the element symbol.
Do not place electrons in pairs until each of the
four sides has one electron (except in Hydrogen).
Lewis dot diagrams can be used to show covalent
bonding.
Bonding:
Atoms are stable when their valence shell of electrons is full. Atoms can gain, lose, or share electrons
with other atoms in order to fill their valence shells.
Covalent bonding: electrons pairs are
shared between two NON-METAL
atoms.
Two atoms can share up to 3
pairs of electrons to fill their valence
shells.
a) Non-polar: electron pairs are
shared evenly because both nuclei
attract the electrons equally.
b) Polar: electron pairs are
shared unevenly because one nucleus
attracts the electrons more strongly
than the other.
This can result in areas of slightly
positive and slightly negative charge in
the molecule (polarity). See water
below.
Ionic bonding: one atom donates an electron to another atom. Both atoms are then ions, the one that
gained the electron will be an anion (negatively charged). Usually a METAL + a NON-METAL atom.
Hydrogen bonding: the weaker attraction
between areas of slight charge on a polar
molecule.
In the diagram of water molecules to the right,
the solid lines represent polar covalent bonds
and the dotted lines represent hydrogen bonds.
During physical changes like evaporation or
freezing, hydrogen bonds would be broken or
formed in large numbers, but the covalent
bonds would remain constant.
Metals and Non-metals:
Metals include most elements. Non-metals
are found on the upper right hand part of
the periodic table.
Lewis Dot Structures and Bonding:
1. Follow the rules of Lewis Dot Structures for each atom in a molecule.
2. Arrange the lone electrons from two atoms into pairs.
3. Repeat until each atom has 8 electrons (or 2 for Hydrogen).
4. IF the above procedure doesn’t work, try sharing multiple pairs of electrons (up to 3 pairs).
A pair of electrons can be shown a pair of dots OR as a single solid line (see below).
Examples of Lewis dot structures:
Methane (CH4):
Oxygen gas (O2):
Naming covalent compounds:
The names of the two elements are stated, but the ending of the second element is changed to –ide.
The prefix (start of the word) indicates the number of each type of atom. (If an element has only one
atom, the mono- prefix can sometimes be dropped.)
Mono = one, Di = two,
Tri = three,
SO2 = sulfur dioxide
N2O3 = dinitrogen trioxide
CCl4 = carbon tetrachloride
H2S = dihydrogen monosulfide
Tetra = four, Penta = five, Hexa = six
Practice problems:
1. Use KMT to explain what happens when you blow
bubbles.
2. a) Discuss what happens at a molecular level when ice melts.
b) Is ice melting and endothermic or exothermic reaction? Explain why.
c) List two things that are the SAME and two things that are DIFFERENT in ice versus liquid water.
Water molecules in ice
Water molecules (liquid)
Same
Same
Different
Different
3. Check all the categories that are true for each sample of matter:
Pure
Mixture Element Compound Heterogeneous Homogenous
substance
mixture
mixture
Oxygen gas (O2)
water (H2O)
salt water (H2O + NaCl)
salt water with sand at
the bottom (H2O + NaCl
+ SiO2)
4. a) Complete the A-Z notation for these atoms:
51
23___
28
___𝑆𝑖
___
___𝐶𝑙
39
______
(if 20 neutrons)
(if 19 protons)
b) For each of the following, give the number of protons, neutrons, and electrons:
# of protons
# of neutrons
7
3𝐿𝑖
80
135𝐵𝑟
7 1+
3𝐿𝑖
5. Determine the average atomic mass for a sample of Strontium that has
10% Strontium-86
5% Strontium-87
85% Strontium-88
6. Fill in the following information on the blank periodic table below:
 Location of metals and non-metals
 Number of valence electrons (Groups 1, 2, and 13-18 only)
 Expected ionic charge (Groups 1, 2, and 13-18 only)
# of electrons
7. a) Draw the Lewis dot structure for the following elements:
Al
O
Ne
b) Use Lewis dot structures to show covalent bonding in the following molecules: Cl2, O2, and CO2.
8. a) Name the following compounds:
N2O3
HBr
H2S
b) Write the formula for the following compouds:
sulfur dioxide
dinitrogen tetrahydride
carbon tetrachloride
9. This graph shows water
demand in 2000 and predicted
water demand in 2050.
a) Looking at the world, name one
area where water demand is
predicted to increase and one
where it is expected to decrease.
Increase:
Decrease:
b) How much water total did
OECD use in 2000?
c) How much water did the world
need for domestic use in 2000?
d) How much is the water demand for electricity in the world expected to change between 2000 and
2050?
e) What percent of BRIICS water demand will be for manufacturing in 2050?