Matter and Energy: Major Understandings
V.1 Matter is classified as a pure substance or as a
mixture of substances. (3.lq)
V.3 A pure substance (element or compound) has
a constant composition and constant properties
throughout a given sample, and from sample to
sample. (3.lr)
Substances
 A substance is any variety of matter all
specimens of which have identical properties
and composition.
 All samples of a particular substance have the
same heat of vaporization, melting point,
boiling point, and other properties related to
composition, which can be used for
identification.
 A substance is homogeneous.
dstreib: Chem Core, Physical Behavior of MatterPage
1 of 19
-1-
Matter and Energy: Major Understandings
V.2 The three phases of matter (solids, liquids,
and gases) have different properties. (3.lkk)
dstreib: Chem Core, Physical Behavior of MatterPage
2 of 19
-2-
Matter and Energy: Major Understandings
V.4 Elements are substances that are composed of
atoms that have the same atomic number.
Elements cannot be broken down by chemical
change. (3.lu)
Elements
 An element is a substance, which cannot be
decomposed by chemical change.
 All samples of an element are composed of
atoms with the same atomic number.
Compounds
 A compound is a substance, which can be
decomposed by a chemical change. A
compound is composed of two or more
different elements chemically combined in a
definite ratio.
 All samples of a compound have identical
composition.
dstreib: Chem Core, Physical Behavior of MatterPage
3 of 19
-3-
Matter and Energy: Major Understandings
V.5 Mixtures are composed of two or more
different substances that can be separated by
physical means. When different substances are
mixed together, a homogeneous or heterogeneous
mixture is formed. (3.ls)
V.6 The proportions of components in a mixture
can be varied. Each component in a mixture
retains its original properties. (3.lt)
V.7 Differences in properties such as density,
particle size, molecular polarity, boiling point and
freezing point, and solubility permit physical
separation of the components of the mixture.
(3.lnn)
dstreib: Chem Core, Physical Behavior of MatterPage
4 of 19
-4-
V.8 A solution is a homogeneous mixture of a
solute dissolved in a solvent. The solubility of a
solute in a given amount of solvent is dependent
on the temperature, the pressure, and the
chemical natures of the solute and solvent. (3.100)
 The component of a solution that is usually a
liquid and is present in excess is called the
solvent, while the other component is called
the solute.
 Concentration of solutions may be indicated
in a variety of ways
V.9 The concentration of a solution may be
expressed as molarity (M), percent by volume,
percent by mass, or parts per million (ppm).
(3.lpp)
 You should also be familiar with the terms
dilute and concentrated; saturated,
unsaturated, and supersaturated; and with
the use and interpretation of the solubility
charts (F & G) in the Reference Tables for
Chemistry.
dstreib: Chem Core, Physical Behavior of MatterPage
5 of 19
-5-
V.10 The addition of a nonvolatile solute to a
solvent causes the boiling point of the solvent
to increase and the freezing point of the
solvent to decrease. The greater the
concentration of particles, the greater the
effect. (3.lqq)
Boiling point elevation
 The presence of a nonvolatile solute raises the
boiling point of the solvent by an amount that
is proportional to the concentration of
dissolved solute particles.
 One mole of particles per 1000 grams of water
raises the boiling point of water 0.52°C.
Freezing point depression
 The presence of a solute lowers the freezing
point of the solvent by an amount that is
proportional to the concentration of dissolved
solute particles.
 One mole of particles per 1000 grams of water
lowers the freezing point of water 1.86°C.
dstreib: Chem Core, Physical Behavior of MatterPage
6 of 19
-6-
V.11 Energy can exist in different forms, such
as chemical, electrical, electromagnetic,
thermal, mechanical, and nuclear. (4.la)
 Heat, light, and electricity are forms of
energy.
 Energy may be converted from one form to
another but is never destroyed in a change.
V.12 Heat is a transfer of energy (usually
thermal energy) from a body of higher
temperature to a body of lower
temperature. Thermal energy is the energy
associated with the random motion of
atoms and molecules. (4.2a)
 Because energy in various forms may be
converted to heat, we use the heat units of
calories, kilocalories, joules or kilojoules to
measure the energies involved in chemical
reactions.
dstreib: Chem Core, Physical Behavior of MatterPage
7 of 19
-7-
V.13 Temperature is a measurement of the
average kinetic energy of the particles in a
sample of material. Temperature is not a
form of energy. (4.2b)
Thermometry
 Temperatures are indicators of the
direction in which heat will flow. Heat flows
spontaneously from a body at higher
temperature to a body at a lower
temperature.
 At the same temperature, the average
kinetic energy of the particles of all bodies is
the same.
Fixed points on a thermometer
 The fixed points on a thermometer are the
ice-water equilibrium temperature at 1
atmosphere pressure, and the steam-water
equilibrium temperature at 1 atmosphere
pressure.
dstreib: Chem Core, Physical Behavior of MatterPage
8 of 19
-8-
 On the Celsius scale the ice-water
equilibrium temperature occurs at 0°C and
the steam-water equilibrium temperature
occurs at 100°C.
 Another scale frequently used in science is
the Kelvin (Absolute) scale on which the icewater equilibrium temperature occurs at
273 K and the steam-water equilibrium
temperature occurs at
373 K.
V.14 The concept of an ideal gas is a model to
explain the behavior of gases. A real gas is
most like an ideal gas when the real gas is at
low pressure and high temperature. (3.4a)
V.17 Kinetic molecular theory describes the
relationships of pressure, volume,
temperature, velocity, and frequency and
force of collisions among gas molecules. (3.4c)
dstreib: Chem Core, Physical Behavior of MatterPage
9 of 19
-9-
V.15 Kinetic molecular theory (KMT) for an
ideal gas states that all gas particles (3.4b):
 are in random, constant, straight-line
motion.
 are separated by great distances relative to
their size; the volume of the gas particles is
considered negligible.
 have no attractive forces between them.
 have collisions that may result in the
transfer of energy between gas particles,
but the total energy of the system remains
constant.
dstreib: Chem Core, Physical Behavior of MatterPage
10 of 19
- 10 -
V.16 Collision theory states that a
reaction is most likely to occur if reactant
particles collide with the proper energy
and orientation. (3.4d)
 Not all of the particles of a gas have the
same kinetic energy, but the average
kinetic energy is proportional to the
measured Kelvin (Absolute) temperature
of the gas.
dstreib: Chem Core, Physical Behavior of MatterPage
11 of 19
- 11 -
V.18 Equal volumes of different gases at the
same temperature and pressure contain an
equal number of particles. (3.4e)
Avogadro’s hypothesis
 Equal volumes of all gases under the same
conditions of temperature and pressure
contain equal numbers of particles.
 For example, at the same temperature
and pressure, the number of particles in 1
liter of hydrogen is the same as the
number of particles in 1 liter of oxygen
although the individual particles of
oxygen are heavier and larger than the
individual particles of hydrogen.
 The amount of matter that contains 6.02 x
102 3 (Avogadro’s number) particles is
called a mole of matter. One mole of any
substance contains as many particles
(molecules, atoms, ions, etc.) as there are
atoms of 12C in 12.000g of 12C isotope.
 Since it is inconvenient to work with
individual particles (atoms, molecules,
ions, electrons, etc.), chemists have chosen
dstreib: Chem Core, Physical Behavior of MatterPage
12 of 19
- 12 -

a unit containing many particles for
comparing amounts of different
materials. The mole is a unit which
contains 6.02 x 102 3 particles.
A mole of particles of any gas occupies a
volume of 22.4 liters at STP.
dstreib: Chem Core, Physical Behavior of MatterPage
13 of 19
- 13 -
V.19 The concepts of kinetic and potential
energy can be used to explain physical
processes that include: fusion (melting),
solidification (freezing), vaporization
(boiling, evaporation), condensation,
sublimation, and deposition. (4.2c)
Vapor pressure
 When a liquid substance changes to a gas the
process is called evaporation. Evaporation
tends to take place at the surface of a liquid
and at all temperatures.
 The term “vapor” is frequently used to refer
to the gas phase of a substance that is
normally a liquid or solid at room
temperature.
 In a closed system the vapor (gas) produced
exerts a pressure that increases as the
temperature of the liquid is raised and is
specific for each substance and temperature.
Boiling point
 A liquid will boil at the temperature at which
the vapor pressure equals the pressure on the
liquid.
dstreib: Chem Core, Physical Behavior of MatterPage
14 of 19
- 14 -
 The normal boiling point is the temperature
at which the vapor pressure of the liquid
equals one atmosphere.
 Usually when reference is made to the
“boiling point” of a substance, it is the normal
boiling point that is indicated.
 Heat of vaporization
 The energy required to vaporize a unit mass
of a liquid at constant temperature is called its
heat of vaporization.
 The energy involved in the change of phase is
required to overcome the forces of attraction
between particles and does not increase their
average kinetic energy. Thus there is no
increase in temperature during this phase
change.
dstreib: Chem Core, Physical Behavior of MatterPage
15 of 19
- 15 -
V.20 A physical change results in the
rearrangement of existing particles in a
substance. A chemical change results in the
formation of different substances with
changed properties. (3.2a)
Some examples of physical changes are:






cutting a piece of paper
ice melting
boiling water
drawing copper into a fine wire
separating out water from seawater
separating out oxygen gas from air
Some examples of chemical changes are:




iron turning into rust in moist air
extracting sulfur from car battery acid
over time, a battery loses its charge
digesting food
dstreib: Chem Core, Physical Behavior of MatterPage
16 of 19
- 16 -
V.21 Chemical and physical changes can be
exothermic or endothermic. (4.lb)
Energy and Chemical Change
 Energy is either absorbed or given off in
chemical changes.
 Molecules absorb energy when chemical
bonds are broken. Energy is liberated
when stronger bonds are formed.




Exothermic reaction
Energy is released in an exothermic
reaction.
Endothermic reaction.
Energy is absorbed in an endothermic
reaction.
Measurement of energy
Because energy in various forms may be
converted to heat, the chemist uses heat
units (joules or kilojoules) to measure the
energies involved in chemical reactions.
Joule
 4.18 joules is the amount of heat required
to raise the temperature of one gram of
water one Celsius degree
 One kilojoule is equivalent to 1000 joules.
dstreib: Chem Core, Physical Behavior of MatterPage
17 of 19
- 17 -
Phases of Matter
 The term “phase” or “ physical state” is
used to refer to the gas, liquid, or solid
form of matter.
 The absorption or release of heat
accompanies change of phase of a
substance.
The above curve if read from right to left, would
illustrate a cooling curve.
dstreib: Chem Core, Physical Behavior of MatterPage
18 of 19
- 18 -
V.22 The structure and arrangement of
particles and their interactions determine the
physical state of a substance at a given
temperature and pressure. (3.ljj)
V.23 Intermolecular forces created by the
unequal distribution of charge result in
varying degrees of attraction between
molecules. Hydrogen bonding is an example
of a strong intermolecular force. (5.2m)
V.24 Physical properties of substances can be
explained in terms of chemical bonds and
intermolecular forces. These properties
include conductivity, malleability, solubility,
hardness, melting point, and boiling point.
(5.2n)
dstreib: Chem Core, Physical Behavior of MatterPage
19 of 19
- 19 -