TAKS Objective 3
Substances have
Chemical and
Physical Properties
The student will demonstrate an
understanding of the structures
and properties of matter.
TEKS Science
Concepts 7.7 B
The student knows that
substances have chemical
and physical properties. The
student is expected to:
Describe physical properties
of elements and identify how
they are used to position an
element on the periodic table.
What is a property?
Properties are defined as
what matter is like and
how it behaves.
Properties are divided into
two major groups:
chemical and physical.
Physical properties
Physical properties are
those that describe what
the matter is like (what
does it look like, feel like,
taste like, etc.). They are
those properties that can
be observed with our
senses.
Examples of
physical properties
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Color
Size
Shape
Density
State of matter
Odor
Texture
Chemical
Properties
• Chemical properties describe
how matter behaves (what
does it do when one type of
matter encounters or reacts
with another.
• Those properties can only be
observed when matter reacts
or doesn’t react.
Examples
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Rusting
Chemical reactivity
Flammability
Combustibility
Physical or
Chemical?
A major test of whether or
not a property is physical
or chemical is whether or
not the property may be
observed without
changing the identity of
the substance. Physical
properties do not change
the identity.
Physical or
Chemical?
• Physical – paper is
wadded up (it is still paper)
• Chemical – paper is
burned (it is no longer
paper)
Engage
Demonstration: Choose
several objects. Keep them
hidden out of view of the
students. Describe each
one using its physical
properties as you observe
the object inside a paper
bag. Allow students to
guess what each object is as
you describe it.
Explore
• Activity: Ornamental
Properties
• Class Time: 20 minutes
• Objective: The student will
demonstrate knowledge of
physical properties by
making an ornament and
listing five physical
properties of that ornament.
Explain
Physical properties are
things that can be
described about an object
or material by observing it
using the five senses.
There are characteristic
physical properties, such
as density and state of
matter, that do not change
regardless of how much of
the material is present.
Elaborate 1
• Activity: The students will
choose 10 of the ornaments that
have been made and place
them into categories based on
their physical properties.
• Class Time: 15 minutes
• Objective: The student will
organize ornaments by similar
physical properties.
Elaborate 2
• Activity: Density, a
Physical Property
• Class Time: 15 minutes
• Objective: The student will
demonstrate that density is a
characteristic property.
Evaluate
• Present students with three items.
You may place them on a table or
in a sack to be given to each
student. The student must list five
physical properties of each item.
• Give each student a density chart
and an unknown element. Allow
them to identify the element based
on its density.
TEKS Science Concepts 7.7 C
The student knows that substances have
chemical and physical properties. The
student is expected to:
Recognize that compounds are composed
of elements.
Periodic Table
The periodic table with which
we are familiar was first
organized in the 1860’s by a
Russian chemist named Dmitri
Mendeleev (Men-da-‘le-off).
Organization
• He looked at properties such
as density, appearance,
atomic mass, melting point,
and compounds formed from
the element.
• Arranged them by increasing
atomic mass in rows and
columns and saw a pattern.
Changes made to the
periodic table
In 1914, a man named Henry
Moseley rearranged the
table in order of increasing
atomic number.
Organization
• Vertical columns are called
groups or families
• Horizontal rows are called
periods
Major divisions
• Metals
• Nonmetals
Alkali Metals
Group 1 elements all
have one electron in
their outer shells. This
gives them similar
properties.
Alkaline Earth
Metals
• Group 2 metals are very
reactive and cannot be
found in nature in pure
form.
• Contain 2 electrons in
the outer shell
Transition metals
Groups 3-12 possess
properties of both metals
and nonmetals and are
therefore called transition
metals.
Halogens
Group 17 elements are
prone to form salts with
metals and are therefore
called “salt formers”.
Noble Gases
• Group 18 elements are all
gases and contain 8
electrons in their outer
shells.
• They are very stable and
nonreactive
Lanthanides and
Actinides
The two groups at the bottom
of the table have been
removed to keep the table
from becoming too wide.
Engage
Activity: Group IT!
Overview: Students
will group types of
transportation based
on passenger
capacity and mode of
transportation.
Explore
• Activity: Periodic
Parallels (Blackline
Master)
• Class Time: 30 minutes
• Objective: The student
will label the periodic
table according to groups
that contain similar
properties.
Explain
The periodic table is organized to show
relationships vertically and horizontally.
The elements in a vertical column (called
group or family) have the same number of
electrons in their outer energy levels. Each
element in a particular horizontal row
(called a period) has the same number of
energy levels as every other element in
that particular row.
Explain
Because elements have the same number of outer
level electrons, they exhibit similar properties.
Some groups are named because of the
properties that they share. For example, the
word “halogen” means “salt-former”. The
elements in group 17 tend to form salts when
combined with other non-metals or metals. They
are also poor conductors of electric current,
react violently with alkali metals to form salts,
and are never found uncombined with other
elements in nature.
Explain
For example, the word “halogen” means
“salt-former”. The elements in group 17
tend to form salts when combined with
other non-metals or metals. They are also
poor conductors of electric current, react
violently with alkali metals to form salts,
and are never found uncombined with
other elements in nature.
Elaborate
Students will do research to
find examples of properties
shared by each specific
group on the periodic table.
For example, alkali metals
react violently with water and
are soft, silvery, and shiny.
Elements in the actinide
period are all radioactive.
Evaluate
Students will be given a
blank copy of the
periodic table to fill in
with the correct names
of the specific groups.
(See Blackline Masters
– Evaluate – Periodic
Parallels)
Elements
Elements are pure
substances that cannot be
broken down into anything
simpler by physical or
chemical means.
Compounds
• Elements combine to form
compounds.
• Compounds may be made
up of only two elements or
many.
Engage
• Activity: Marshmallow
molecules
• Class Time: 20 minutes
• Objective: The student will
construct a model of a water
molecule using
marshmallows
Explore
• Activity: Electrolysis of Water
(Student Worksheet that comes
with lab kit)
• Class Time: 50 minutes
• Objectives:
• The student will conduct a
decomposition reaction in which
water is broken down into
hydrogen and oxygen and each
gas is collected into a separate
test tube.
• The student will demonstrate how
compounds are composed of
elements.
Explain
Water molecules are composed of two
atoms of hydrogen joined with one
atom of oxygen. The bonds formed are
covalent bonds in which electrons are
shared, but when a substance such as
salt is dissolved in the water, the atoms
are separated, forming ions (atoms
with a positive or negative charge).
Explain
The hydrogen atoms leave their one
electron with the oxygen atom
resulting in hydrogen now being a
positive ion (minus one electron) and
oxygen being a negative ion (gaining
two electrons, one from each
hydrogen atom).
Explain
Once the system is connected to the
battery, a current begins to flow. One
electrode underneath one test tube
becomes positively charged and the other
electrode underneath the other test tube
becomes negatively charged. The
pathway from the negative electrode to the
positive electrode is accomplished by an
electrolyte solution (a solution which
conducts electricity) such as salt water.
Explain
The now positive hydrogen ions are
attracted to the negative electrode and the
negatively charged oxygen ions are
attracted to the positive electrode. As the
gases collect on the electrodes, it is very
obvious. Large bubbles appear on the +
electrode (oxygen) and thousands of very
tiny bubbles (hydrogen) appear on the –
electrode.
Elaborate
• Activity: Combining some
elements with oxygen.
(Activity #7) (Students will
use the student worksheet
from the lab kit)
• Class Time: 15 minutes
• Objective: The students
will synthesize compounds
from elements.
Explain
• When elements combine to
form compounds they are
brand new substances with
completely unique
properties.
• They no longer possess the
properties of the elements
that formed them.
Evaluate
The students will journal
about what they learned
concerning the formation
of compounds from
elements. They should
cite examples learned
from the lab experience.