TAKS Objective 3 Substances have Chemical and Physical Properties

1
TAKS Objective 3 Substances have Chemical and
Physical Properties

• The student will demonstrate an understanding of
  the structures and properties of matter.

2
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.

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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.

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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.

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Examples of physical properties

• Color
• Size
• Shape
• Density
• State of matter
• Odor
• Texture

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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 doesnt react.

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Examples

• Rusting
• Chemical reactivity
• Flammability
• Combustibility

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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.

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Physical or Chemical?

• Physical paper is wadded up (it is still paper)
• Chemical paper is burned (it is no longer
  paper)

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?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.

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?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.

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?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.

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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.

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Elaborate 2

• Activity Density, a Physical Property
• Class Time 15 minutes
• Objective The student will demonstrate that
  density is a characteristic property.

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?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.

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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.

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Periodic Table

• The periodic table with which we are familiar
  was first organized in the 1860s by a Russian
  chemist named Dmitri Mendeleev (Men-da-le-off).

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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.

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Changes made to the periodic table

• In 1914, a man named Henry Moseley rearranged
  the table in order of increasing atomic number.

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Organization

• Vertical columns are called groups or families
• Horizontal rows are called periods

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Major divisions

• Metals
• Nonmetals

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Alkali Metals

• Group 1 elements all have one electron in
  their outer shells. This gives them similar
  properties.

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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

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Transition metals

• Groups 3-12 possess properties of both metals
  and nonmetals and are therefore called transition
  metals.

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Halogens

• Group 17 elements are prone to form salts with
  metals and are therefore called salt formers.

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Noble Gases

• Group 18 elements are all gases and contain 8
  electrons in their outer shells.
• They are very stable and nonreactive

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Lanthanides and Actinides

• The two groups at the bottom of the table have
  been removed to keep the table from becoming too
  wide.

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?Engage

• Activity Group IT!
• Overview Students will group types of
  transportation based on passenger capacity and
  mode of transportation.

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?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.

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?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.

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?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.

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?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.

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?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.

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?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)

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Elements

• Elements are pure substances that cannot be
  broken down into anything simpler by physical or
  chemical means.

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Compounds

• Elements combine to form compounds.
• Compounds may be made up of only two elements or
  many.

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?Engage

• Activity Marshmallow molecules
• Class Time 20 minutes
• Objective The student will construct a model of
  a water molecule using marshmallows

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?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.

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?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).

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?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).

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?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.

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?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.

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?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.

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?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.

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?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.