Chapter 3: Matter and Energy
 Distinguish between physical and
chemical properties.
 Distinguish between physical and
chemical changes.
 Apply the law of conservation of mass.
 Physical property: a property that a
substance displays without changing its
composition.
 Chemical property: a property that a
substance displays only through changing
its composition.
melting point
mass
state of matter
color
flammability
reacts with an acid
reacts with oxygen
 Gasoline:
 Physical property: its characteristic odor
▪ gasoline does not change its composition when it
exhibits its odor
 Chemical property: its flammability
▪ gasoline does change its composition when it
burns
 The atomic or molecular composition of
a substance does not change when the
substance displays its physical
properties.
 A chemical or physical property can also be
described as either intensive or extensive.
 Intensive Properties: Properties that do
not depend on the amount of substance
present
 Examples: color, melting point, density, luster
 Extensive Properties: Properties that
do depend on the amount of substance
present.
 Examples: mass, volume, amount of
energy within a substance

Physical property: the boiling
point of water
 How is the water changing once it
boils?

When water boils, it turns into a
gas, but the water molecules are
the same in both the liquid water
and the gaseous steam.
 Physical change: matter changes its
appearance but not its composition
 When ice melts, it looks different but its
molecular composition is the same. Solid ice
and liquid water are both composed of water
molecules, so melting is a physical change.
 Chemical change: matter does change
its composition
 For example, copper turns green upon
continued exposure to air because it reacts
with gases in air to form new compounds.
This is a chemical change.
 State changes: transformations from
one state of matter to another, such as
from solid to liquid
 These are always physical changes

Condensation

 Liquid to gas
 Gas to liquid

Freezing

Melting
 Solid to liquid
Sublimation
 Solid to gas
 Liquid to solid

Evaporating

Deposition
 Gas to solid
cutting
boiling
breaking
tearing
Four good indications of a chemical change...
color change
gas released
(often with an
odor)
energy change
(light, heat, …)
precipitate
formed

A chemical property: The
susceptibility of iron to
rusting.
 Is rusting a physical or
chemical change?

When iron rusts, it turns
from iron to iron oxide.

Classify each property as physical or chemical.
a) the tendency of copper to turn green when exposed to air
b) the tendency of automobile paint to dull over time
c) the tendency of gasoline to evaporate quickly when spilled
d) the low mass (for a given volume) of aluminum relative to other
metals

Matter undergoes a chemical change when it undergoes
a chemical reaction.

In a chemical reaction, the substances present before the
chemical change are called reactants. The substances
present after the change are called products.
 The difference between chemical and
physical changes is seen at the molecular
and atomic level.

In physical changes, the atoms that
compose the matter do not change
their fundamental associations, even
though the matter may change its
appearance.
 A physical change results in a different
form of the same substance.

In chemical changes, atoms
do change their
fundamental associations,
resulting in matter with a
new identity.
 A chemical change results in
a completely new substance.

Classify each change as physical or chemical.
a) the rusting of iron
b) the evaporation of fingernail-polish remover (acetone)
from the skin
c) the burning of coal
d) the fading of a carpet upon repeated exposure to
sunlight

In this figure liquid water is
vaporizing into steam.
 Which diagram best represents
the molecules in the steam?
 Compounds are pure substances
 Compounds can only be separated by chemical
reactions.
 Mixtures can never consist of only a single
substance
 Mixtures can be separated by physical changes
 Filtration
 Separates liquid from a solid
 The mixture is poured over a
mesh-like filter paper and
the liquid is allows to pass
through, leaving behind the
solid
 Density
 Liquids of different densities
will separate into layers.
 The lowest density liquid will
rest on top.

Centrifuge
 A centrifuge is a machine that
separates solids from liquids by
spinning very quickly.
 This causes solids to fall to the
bottom of the test tube,
separating them from the
liquids in the mixture.

Decant
 Separates solid from liquid by
pouring the liquid off the top
and leaving the solid behind
 It can be difficult to ensure that
all of the liquid is removed by
this technique

Magnetism
 Can be used to remove
magnetic solids from a
mixture
 Magnetic elements
include iron, nickel, and
cobalt

Distillation
 To separate a mixture of liquids, the liquid can be
heated to force components, which have different
boiling points, into the gas phase. The gas is then
condensed back into liquid form and collected.
 Can be used to separate several different
substances
 Chromatography
 Techniques which use a stationary phase
(e.g. paper) and a mobile phase (e.g. some
sort of solvent like water or alcohol) to
physically separate substances.

A sample of the mixture is placed on the paper (stationary
phase). The solvent will then dissolve the components of the
mixture.

The components of the mixture will move with the solvent
(mobile phase) up the paper.

Based on the properties of each component (e.g., polarity) the
components will travel at different speeds with the solvent.

Many complex variations, but basic principles stay the same

Law of Conservation of Mass: matter is
neither created nor destroyed in a chemical
reaction.
 In a nuclear reaction, significant changes in mass
can occur.

During physical and chemical changes, the
total amount of matter remains constant.

Suppose that we burn 58 g of butane in a
lighter. It will react with 208 g of oxygen to
form 176 g of carbon dioxide and 90 g of water.

A chemist forms 16.6 g of potassium iodide by
combining 3.9 g of potassium with 12.7 g of
iodine. Show that these results are consistent
with the law of conservation of mass.

Suppose 12 g of natural gas combines with 48 g
of oxygen in a flame. The chemical change
produces 33 g of carbon dioxide. How many
grams of water form?

Classify each property as physical or chemical.

(a) the explosiveness of hydrogen gas

(b) the bronze color of copper

(c) the shiny appearance of silver

(d) the ability of dry ice to sublime (change from solid directly to
vapor)

Classify each change as physical or chemical.

(a) copper metal forming a blue solution when it is dropped into colorless nitric acid

(b) a train flattening a penny placed on a railroad track

(c) ice melting into liquid water

(d) a match igniting a firework
 Consider a drop of water that is put into
a flask, sealed with a cap, and heated
until the droplet vaporizes. Is the mass
of the container and water different
after heating?