Physical Science
Changes in Matter
Benchmarks
IV.2.MS.1
IV.2.MS.2
IV.2.MS.3
Benchmarks

Describe common physical changes in
matter: evaporation, condensation, thermal
expansion, contraction. (IV.2.MS.1)

Describe common chemical changes in
terms of properties of reactants and
products. (IV.2.MS.2)

Explain physical changes in terms of the
arrangement and motion of atoms and
molecules. (IV.2.MS.3)
3 States of Matter

There are 3 major states of matter, they
are…
Solids
 Liquids
 Gasses

In all three states of matter, molecules are
in constant motion.
And yet another phase of matter…

Plasma is another phase of matter that is
sometimes recognized by scientists.

It is a state above the gas phase.

Click the link to see another explanation of the
states of matter.
 http://www.chem4kids.com/files/matter_states.html
Solids
In a solid, relatively strong forces are
exerted between the molecules, so the
molecules of the material vibrate
slowly.
 Solids, therefore, have a definite shape
and volume.

Liquids
When heat energy is added, the
molecules vibrate faster as they absorb
the energy.
 At the melting temperature of the
material, the molecules have gained
enough energy, so that they can slip
and slide past each other.
 The material is now a liquid.

Gasses
Liquids still have a definite volume, but
take the shape of their container.
 When more heat energy is added, the
motion of the molecules within the
liquid increases, until some of the
molecules overcome the forces,
becoming a gas.
 The liquid has now evaporated to a gas.

The reverse is also true
Gas molecules are separated by
relatively great distances and move
about freely.
 Gases take the shape and volume of
their container.
 Conversely, when enough energy is
lost from gas molecules, they
condense into the liquid phase.

Condensation
Freezing
Contract
more heat energy
less heat energy
+E
-E
States of Matter
warmer
Plasma
colder
Gas
Liquid
Solid
(water vapor)
(water)
(ice)
No definite shape
No definite shape
Definite shape
No definite volume
Definite volume
Definite volume
Evaporation
Melting
Expand
BEC
Thermal Expansion

As a solid is heated, particles move faster
and faster and vibrate against each other
with more force.

As a result, the particles spread apart slightly
in all directions and the solid expands.

The same effect also occurs in liquids and
gases.
Thermal Expansion

Almost all matter expands as it gets
hotter and contracts as it cools.

This characteristic of matter is called
thermal expansion.

This happens because in a solid, forces
between the particles hold them
together.
Thermal expansion

Since this phenomenon
occurs in bridges,
expansion joints allow
bridges to expand in warm
weather without cracking.
Can you imagine the
effect that thermal
expansion and
contraction might have
on our roads?
Heat and Phases of Matter

Heat affects
the phases
of matter.
View this
video clip to
see how.
Introduction

There are two types of properties of
matter, they are physical properties and
chemical properties.

There are also two types of changes in
matter they are physical changes and
chemical changes.

Let’s talk about physical properties first.
Physical Properties

A physical property is any
characteristic of a material that one can
observe easily without changing the
substances that make up the material.

Every substance has physical
properties that distinguish it from other
substances.
Physical Properties

Physical property examples…










shape
Size
Color
Smell
Temperature
Volume
Density
melting point
boiling point
state of matter.
Physical Changes
A change in physical properties is
called a physical change.
 Physical changes do not alter the
identity of a substance.
 Pounding, pulling, cutting, dissolving,
melting, or boiling do not produce a
new substance with new properties, so
they are all physical changes.

Physical Change Example
For example if you take a piece of
paper and tear it into pieces you still
have paper. It may be smaller, but it’s
still paper.
 You could dye the paper and make it
another color, but it’s still paper.
 You have only changed it physically.

Physical Changes

When trying to identify a physical change,
it is important to know that physical
changes can be reversed.

For example…
 Pieces
of paper can be reformed into a new whole
sheet.
 Ice can be melted, or boiled and then refrozen.
Physical Changes of Water
Freezing-liquid to a solid; this change requires
cooling
Melting-solid to a liquid: this change is speeded up
by heating.
Condensation-gases change to a liquid; this
change requires cooling.
Vaporization/Evaporation-liquid changes to gas;
this change is speeded up by heating.
Sublimation-gas changes to a solid or a solid
changes to a gas without passing through the
liquid state (e.g., dry ice, solid to gas)
What Do You Think?
Can you name
this physical
change of water?
 Here’s a hint: The
water is changing
from the gas to
the liquid phase.

What Do You Think?
Can you name
this physical
change of water?
 Here’s a hint: The
water is changing
from the liquid to
the gas phase.

Review Video

That was a lot of
information. Let’s
review physical
properties and
physical changes
with a look at this
video clip on
states of matter.
(18 min)
Chemical Properties/Changes

Substances
can change
their
identities,
for example,
fireworks
explode,
Chemical Properties/Changes

matches
burn
Chemical Properties/Changes

Food cooks
Chemical Properties/Changes

And iron
rusts
Chemical Properties/Changes

Burned toast, burned soup, and burned
steak all smell burned. The smell is
different from the smell of bread, soup, or
steak.

The odor is a clue that a new substance
has been produced.
Chemical Property

A chemical property
is a characteristic of
a substance that
indicates if it can
undergo a certain
chemical change.

Click the picture for a
video clip about
chemical properties.
Chemical Change

A change of one substance in a material to a
different substance is a chemical change.

In some chemical changes a rapid
production of energy, such as the production
of heat, light, sound or gas bubbles occur.
These things indicate that a chemical change
has occurred.

Burning and rusting are chemical changes
because different substances are produced.
Chemical Change

A baked cake no longer resembles its
ingredients of flour, eggs, butter, and sugar,
because the reactants have undergone a
chemical change.
product
reactants

A chemical reaction is simply breaking substances (reactants) apart
and making new ones (products) from the pieces.
Chemical Changes

When trying to identify a chemical change,
it is important to know that chemical
changes can NOT be reversed.

For example…
 A cake
can not be broken down into eggs, sugar,
flour, and butter.
 You can not un burn a piece of wood.
Chemical Reactions

Those ingredients have been changed
by a chemical reaction.

A chemical reaction is simply breaking
substances (reactants) apart and
making new substances (products)
from the pieces.
Chemical Reactions

Whenever a chemical reaction takes
place, new substances, the products,
are made.

These have very different properties
from the original starting materials, the
reactants.
reactant + reactant = product
Chemical Reactions

This process involves the
rearrangement of atoms and molecules,
and the making and breaking of
chemical bonds.
Closed System

The mass remains constant, because a
chemical reaction is a closed system and no
matter is lost.

Closed system: a system in which the total mass
of each element in the system remains constant
before as well as after any kind of chemical or
physical change.

No matter is ever created or destroyed during
the change.
Chemical Changes

Here’s a video
clip that may
explain
chemical
changes more
clearly.
Physical & Chemical Changes

Click the links to hear a science guys song
on…

Physical Changes

Chemical Changes