Academic Standard 7-5
7-5
Topic: The Chemical Nature of Matter
The student will demonstrate an understanding of the classifications and properties of
matter and the changes that matter undergoes. (Physical Science)
Key Concepts
Matter: atoms, elements, compounds, mixtures
Physical Properties: melting point, boiling point, density, color
Chemical Properties: reactivity, ability to burn, ability to rust
Elements: metals, nonmetals
Periodic Table: groups and families of elements
Common substances: chemical symbols, chemical formulas
Law of Conservation of Matter: balanced chemical equation, reactants, products
Acids and Bases: indicators, litmus paper, pH paper, phenolphthalein, pH
Physical changes: changes in size, shape, and state
Chemical changes: changes in color or temperature, formation of precipitate or gas
Indicators:
7-5.1 Recognize that matter is composed of extremely small particles called atoms.
Taxonomy level: 1.1-B Remember Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of matter being
composed of very small particles in 5th grade (5-5.1). Students have not been introduced to the
concept of atoms in previous grades. Students will further develop the concept of atoms in 9th grade
Physical Science (PS-2.1 and PS-2.2).
It is essential for students to know that matter is composed of extremely small particles called
atoms and that atoms are the smallest part of pure substances that cannot be broken down into
simpler substances.
It is not essential for students to know the subatomic particles, for example, protons, neutrons,
and electrons, which compose atoms.
Assessment Guidelines:
The objective of this indicator is to recognize that matter is composed of extremely small particles
called atoms; therefore, the primary focus of assessment should be to recall from long-term memory
the information that atoms are the extremely small particles of matter. However, appropriate
assessments should also require students to identify extremely small particles of matter as atoms.
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Academic Standard 7-5
7-5.2
Topic: The Chemical Nature of Matter
Classify matter as element, compound, or mixture on the basis of its composition.
Taxonomy Level: 2.3-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of mixtures in 5th grade
(5-4.3). Students have not been introduced to the concept of elements or compounds in previous
grades. Students will further develop the concepts of elements, compounds, and mixtures in high
school Physical Science (PS-3.4).
It is essential for students to know that matter can be classified on the basis of its composition as
follows:
Elements
Elements are pure substances that cannot be changed into simpler substances.
Elements are composed of one type of atom.
Compounds
Compounds are pure substances that are composed of two or more types of elements.
Compounds can only be changed into simpler substances called elements by
chemical changes (7-5.10), which are not as easy as separating mixtures into their
components.
Mixtures
Mixtures are composed of different substances that are mixed together. They can be
separated easily into their component substances by processes described in 5th grade
(5-4.4).
It is not essential for students to know that atoms combine to form molecules, which are the
smallest part of compounds. Students also do not need to know that mixtures can be heterogeneous
or homogeneous.
Assessment Guidelines:
The objective of this indicator is to classify matter as element, compound, or mixture on the basis of
its composition; therefore, the primary focus of assessment should be to categorize matter as
elements, compounds or mixtures depending on its composition. However, appropriate assessments
should require students to recognize the classifications of matter based on its composition; to
exemplify (give examples of) matter based on its composition; to illustrate with words, pictures, or
diagrams categories of matter; to infer the types of matter based on characteristics; to compare the
types of matter based on their characteristics.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.3. Compare the physical properties of metals and nonmetals.
Taxonomy Level: 2.6-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of physical properties
in 5th grade (5-4.2). Students have not been introduced the concept metals and nonmetals in
previous grade levels. Students will further develop the concepts of metals and nonmetals in 9th
grade Physical Science (PS-2.3)
It is essential for students to know that metals and nonmetals are two major groups of elements
that have different physical properties as follows:
Metals
Nonmetals
Physical properties of metals include the following:
Luster
Having a shiny surface or reflecting light brightly
Conductors
Heat and electricity move through them easily.
Malleable
Ability to be hammered into different shapes
Ductile
Ability to be drawn into a wire
High density
Heavy for their size
Physical properties of nonmetals include the following:
Dull
Not shiny
Nonconductors
Heat and electricity do not move through them easily
Brittle
Break or shatter easily
It is not essential for students to know the chemical properties of metals versus nonmetals, or the
electron arrangement in atoms of metals versus nonmetals.
Assessment Guidelines:
The objective of this indicator is to compare the physical properties of metals and nonmetals;
therefore, the primary focus of assessment should be to determine the differences between metals or
nonmetals based on their physical properties. However, appropriate assessments should also
require students to infer from a list of physical properties whether an object is metal or nonmetal; to
recall physical properties of metals and nonmetals; or to summarize physical properties of metals
and nonmetals.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.4 Use the periodic table to identify the basic organization of elements and groups of
elements (including metals, nonmetals, and families).
Taxonomy Level: 3.2-B Apply Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced to the periodic table in previous
grade levels. Students will further develop the concept of the periodic table in 9th grade Physical
Science (PS-2.3).
It is essential for students to know how to use the periodic table to identify the basic organization
of elements. The elements on the periodic table are identified with numbers increasing from left to
right across each row of the table. Along with this number (atomic number) there is also a symbol
that identifies each element on the table. There are two large sections of elements on the periodic
table. On the periodic table there is a zigzag line on the right side of the table. Metals are to the left
of this line. Nonmetals are to the right.
Families
Also called groups, are columns of elements on the periodic table that have many
similar properties; they are usually numbered 1-18. A family of elements has some
chemical characteristics that are similar.
Metals
Groups A major classification of elements generally located on the left side of the
periodic table. Examples on metals are: Sodium (Na), Calcium (Ca), Iron (Fe), and
Aluminum (Al).
Nonmetal
Families A major classification of elements generally located on the right side of the
periodic table. Examples of nonmetals are: Chlorine (Cl), Oxygen (O), Sulfur (S),
and Iodine (I).
It is not essential for students to know how each element gets its atomic number (no subatomic
particles are part of this standard). They do not need to know the names of the individual families
or groups of elements or to identify metalloids.
Assessment Guidelines:
The objective of this indicator is to use the periodic table to identify the basic organization of
elements on the periodic table, the metal and nonmetal divisions, and to locate families of elements;
therefore, the primary focus of assessment should be to retrieve knowledge about the periodic table
as identified. However, appropriate assessments should also require students to exemplify elements
that are metals and nonmetals given a periodic table; recognize the location of an element on the
periodic table; recognize the location of groups of metals and nonmetals; to recognize that families
are columns of elements; or identify an element based on its atomic number or symbol.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.5 Translate chemical symbols and the chemical formulas of common substances to show
the component parts of the substances (including NaCl [salt], H20 [water], C6H1206
[simple sugar], 02 [oxygen gas], C02 [carbon dioxide], and N2 [nitrogen gas]).
Taxonomy Level: 2.1-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced to the concepts of chemical
symbols and the chemical formulas in previous grades. Students will further develop the concepts of
chemical symbols and chemical formulas in 9th grade Physical Science (PS-4.5).
It is essential for students to know that chemical symbols show the atoms of the elements
composing a substance. Atoms of common elements have different symbols as follows:
Symbol
Na
Cl
H
0
C
N
Element
Sodium
Chlorine
Hydrogen
Oxygen
Carbon
Nitrogen
Chemical formulas are constructed from the symbols of the elements composing the substances.
Elements are made up of one type of atom and their formulas have one symbol. Compounds are
composed of more than one element and their formulas have more than one type of symbol showing
the different atoms that compose the compound. In a chemical formula, the numbers as subscripts
show the ratio of the number of atoms of the different elements in the compound.
It is not essential for students to know chemical symbols and chemical formulas for substances
not listed in 7-5.5.
Assessment Guidelines
The objective of this indicator is to translate chemical symbols and chemical formulas of common
substances listed above to show the component parts; therefore, the primary focus of assessment
should be to interpret a chemical symbol and formula to identify the element(s) and the number of
atoms of that element in a formula of the substance. However, appropriate assessments should also
require students to recognize the chemical symbols and formulas of common substances to recall
the components.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.6 Distinguish between acids and bases and use indicators (including litmus paper, pH
paper, and phenolphthalein) to determine their relative pH.
Taxonomy level: 4.1-B Analyze Conceptual Knowledge
Previous/Future knowledge: Students have been introduced the concept of solutions, solvents,
solutes, and concentrations in 5th grade (5-4.5). Students have not been introduced to the concept of
solutions of acids and bases nor their concentrations in previous grades. They will further develop
these concepts of acids and bases in 9th grade Physical Science (PS-3.8).
It is essential for students to know that acids and bases are solutions usually with water as the solvent:
Acids
Acids can be identified by their sour taste (lemons and oranges contain acids)—but
students should not use a taste test on laboratory chemicals; by their reaction with
some metals (for example, zinc), and by their reaction with bases to form a neutral pH
solution.
Bases
Bases can be identified by their bitter taste (soapsuds have a bitter taste)—but students
should not use a taste test on laboratory chemicals; by their slippery feels when rubbed
between thumb and fingers---but some strong bases burn the skin so this test should
not be used; and by their reaction with acids to form a neutral pH solution.
pH
pH is a measure of the concentration of solutions of acids and bases and is measured
on a scale of 1-14. A basic solution has a pH greater than 7 and an acidic solution has a
pH less than 7. If a solution is neither an acid nor a base, it has a pH of 7 and is called
neutral. Pure water has a pH of 7. The stronger the acid, the lower the pH (less than
7) while the stronger the base, the higher the pH (greater than 7).
Indicators
Indicators are substances that can be used to determine the whether a solution is an
acid or base. The following indicators can be used to determine relative pH
Litmus paper
Blue litmus paper turns red in an acid, and stays blue in a base. Red
litmus paper turns blue in a base, and stays red in an acid. Both red
and blue litmus paper turn purple in a solution that is neutral
(neither an acid nor a base).
pH paper
pH paper can turn a series of colors in solutions of pH. The color of
the paper is compared to the chart of the vial to determine the pH.
Phenolphthalein Phenolphthalein turns magenta in a strong base and stays clear in an
acid
It is not essential for students to know the specific colors of pH paper at given pH ranges, that a
solution is called “neutral” if it is neither an acid or a base, or how to neutralize a solution to form
water and salt.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
Assessment Guidelines:
One objective of this indicator is to distinguish between acids and bases, therefore, the primary
focus of assessment should be to analyze properties of solutions to determine whether they are acids
or bases. Another objective is to use indicators to determine relative pH; therefore, the primary
focus of assessment should be to apply a procedure that uses indicators to determine the relative
acidic or basic concentration of the solutions. However, appropriate assessments should also
require students to identify solutions as acidic or basic based on properties; to identify solutions as
more acidic or more basic depending on pH results with indicators; summarize the use of indicators
in determining the pH of a solution; or infer the pH of a solution given the results of a particular
indicator.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.7 Identify the reactants and products in chemical equations.
Taxonomy Level: 1.1-B Remember Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of forming new
substances when they chemically combine in 5th grade (5-4.7). Students have not been introduced
to the concept of reactants or products or chemical equations in previous grades. Students will
further develop the concept of chemical reactions and equations in 9th grade Physical Science (PS4.6 and PS-4.7).
It is essential for students to know that when substances are mixed and at least one new substance
is formed, a chemical reaction has occurred.
Chemical equations
Are used to represent chemical reactions that have occurred. They contain the
chemical formulas (7-5.5) for the substances that are mixed and the new
substance(s) that are formed. An arrow separates them.
Reactants
The substances that are mixed in a chemical reaction are called the reactants
and appear on the left side of the arrow in a chemical equation.
Products
The new substances that are formed in a chemical reaction are called the
products and appear on the right side of the arrow in a chemical equation.
For example, the following chemical equation shows the formation of water (H20) from oxygen (02)
and hydrogen (H2). The reactants are oxygen (02) and hydrogen (H2), located on the left side of the
arrow. The product, water (H20), is on the right side of the arrow.
2H2 + 02 →
Reactants →
2H20
Products
It is not essential for students to know how to balance chemical equations by adding coefficients
in front of the chemical formulas or to name the various types of chemical reactions that occur (for
example, single displacement, double displacement, decomposition, or synthesis).
Assessment Guidelines:
The objective of this indicator is to identify reactants and products in chemical equations; therefore,
the primary focus of assessment should be to recognize the reactants and products in a chemical
equation. However, appropriate assessments should also require students to recall that reactants are
before the chemical reaction and products are after the chemical reaction shown by the arrow of the
equation.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.8 Explain how a balanced chemical equation supports the law of conservation of matter.
Taxonomy Level: 2.7-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of the law of
conservation of energy during energy transformations in 6th grade (6-5.2). Students have not been
introduced to the concept of the law of conservation of matter in previous grades. Students develop
the concept of chemical equations in this grade (7-5.7). Students will further develop this concept of
balanced chemical equations and conservation of mass in 9th grade Physical Science (PS-4.7).
It is essential for students to know that the amount of matter does not change during a chemical
reaction; only the atoms are rearranged to form new substances. The law of conservation of matter
is based on countless experiments in which the mass of the reactants has been found to equal the
mass of the products. The law of conservation of matter states that matter can neither be created nor
destroyed, but can be changed in form. In other words, the total mass of the material(s) before the
reaction is the same as the total mass of material(s) after the reaction.
A balanced chemical equation has the same number of each kind of atom on both sides of the
arrow. When students multiply the number in front of the chemical formula in the equation by each
number written below the symbol of the atoms in the formula, the number of each kind of atom on
the left side of the arrow must equal the number of each kind of atom on the right side of the arrow
for the equation to be balanced
In the chemical equation for the reaction of water (liquid) changing to hydrogen and oxygen (gas)
2H20  2H2 + 02



There are 2 x 2 Hydrogen (H) = 4 Hydrogen (H) atoms on the left of the arrow and 2 x 2
Hydrogen (H) = 4 Hydrogen (H) atoms on the right of the arrow;
There are 2 x 1 Oxygen (O)= 2 Oxygen (O) atoms on the left of the arrow and 1 x 2 Oxygen (O)
atoms on the right of the arrow; (if no number appears in front of the formula or below the atom,
it is an understood “1”).
Therefore, there are the same numbers of atoms of hydrogen (4) and oxygen (2) on both sides of
the equation and the equation is said to be balanced.
Since there are the same number of each kind of atom on both sides of the arrow and atoms
represent kinds of matter, the amount of matter is the same on both sides of the equation, which
supports the law of conservation of matter.
It is not essential for students to know how to add numbers in front of chemical formulas to
balance chemical equations. They must only recognize a balanced equation. They do not have to
know how to create the chemical formulas for substances. They must only analyze given formulas
for common substances to show the component parts.
Assessment Guidelines:
The objective of this indicator is to explain how a balanced equation supports the law of
conservation of matter; therefore the primary focus of assessment should be to construct cause and
effect models of how a balanced equation supports the law of conservation of matter. However,
appropriate assessments should also require students to recall the law of conservation of matter;
summarize how the law of conservation of matter relates to a balanced equation; or recognize
whether or not a chemical equation is balanced or not.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.9 Compare physical properties of matter (including melting or boiling point, density, and
color) to the chemical property of reactivity with a certain substance (including the
ability to burn or to rust).
Taxonomy level: 2.6-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of properties of matter
in 2nd grade (2-4.1), in 3rd grade (3-4.1), and physical properties of the states of matter in 5th grade
(5-4.2). Students have not been introduced to the concept of physical properties or chemical
properties of matter in previous grades. Students will further develop the concept of physical and
chemical properties in 9th grade Physical Science (PS-3.1).
It is essential for students to know that physical properties of matter can be observed and
measured without changing the kind of matter being studied. Chemical properties are not usually
visible. They can be recognized only when substances react chemically with one another, that is,
when they undergo a change in composition. The following physical properties can be used to help
identify a substance:
Melting Point Melting point is the temperature at which a solid can change to a liquid. The
temperature at which a pure substance melts is unchanging. Therefore, the melting
point of a pure substance can be used as a physical property for identifying it. Ice
melts to form water at 00C or 32oF.
Boiling Point Boiling point is the temperature at which a liquid changes state into a gas. The liquid
starts to form bubbles throughout, which grow larger, rise to the surface, and burst.
This temperature is unchanging for a given substance, at sea level, and can be used to
identify that substance. The boiling point for pure water is 100oC or 212oF.
Density
Density, defined qualitatively, is the measure of the relative “heaviness” of objects
with a constant volume, is the mass of a given volume of a substance. The density of
a given substance is unchanging and can be used as a physical property to identify it.
The density of water is a universal standard: 1 milliliter of water (at 4oC) equals 1
cubic centimeter of water equals 1 gram of water. The density of water is 1 g/mL or
1 g/cm3 or 1g/cc. Lead for example is a very heavy, dense metal. The density of
lead is much greater than the density of the very light metal, aluminum.
Color
Color of a given substance is distinctive and can be used to help identify a substance.
Chemical properties can also be used to help identify a substance. Chemical properties are not
usually visible. Chemical properties can be recognized only when substances react chemically with
one another, that is, when they undergo a change in composition.
 Chemical reactivity is the tendency of a substance to undergo a chemical reaction usually with
other specific substances.
 When a substance reacts with oxygen quickly and releases heat and light energy, the process is
called burning.
 When a substance, for example iron, reacts with oxygen and water slowly, the process is called
rusting.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
It is not essential for students to calculate the density of substances if given the mass and the
volume of the substances.
Assessment Guidelines
The objective of this indicator is to compare physical and chemical properties of matter; therefore,
the primary focus of assessment should be to determine the differences between physical and
chemical properties of matter. However, appropriate assessments should also require students to
classify properties as being physical or chemical; to summarize how physical or chemical properties
help identify substances; or exemplify (give examples of) physical and chemical properties used to
identify substances.
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Academic Standard 7-5
Topic: The Chemical Nature of Matter
7-5.10 Compare physical changes (including changes in size, shape, and state) to chemical
changes that are the result of chemical reactions (including changes in color or
temperature and formation of a precipitate or gas).
Taxonomy Level: 2.6-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced to the concepts of physical or
chemical changes before this grade level. They will further develop the concept of physical and
chemical changes in 9th grade Physical Science (PS-4.6).
It is essential for students to know that physical changes do not change the identity of a substance.
When a substance changes state, the substance does not change identity. A change in state,
therefore, is a physical change. When substances change in size or shape, they do not change
identity; therefore, these changes are also physical changes.
When the following changes occur, however, the substance usually changes identity; therefore, the
changes are chemical changes:
Color change
When a substance changes color, the chemical composition of the substance
has usually changed; therefore, this is a chemical change.
Temperature change When substances change temperature after being mixed with other
substances, the chemical composition of the substances has usually changed;
therefore, this is a chemical change.
Precipitate formation When two or more liquids are mixed and a solid (precipitate) forms, the
chemical composition of the substances has usually changed; therefore, this is
a chemical change.
Gas formation
When substances are mixed or heated and a gas is given off, the chemical
composition of the substances has usually changed; therefore, this is a
chemical change.
It is not essential for students to identify the type of chemical change that has occurred, nor to
identify a reaction as exothermic or endothermic depending on the temperature change.
Assessment Guidelines
The objective of this indicator is to compare physical and chemical changes; therefore, the primary
focus of assessment should be to determine how physical and chemical changes are alike and
different. However, appropriate assessments should also require students to exemplify (give
examples of) physical and chemical changes; to infer if a physical or chemical change has occurred
based on the conditions given; or to classify changes as chemical or physical based on descriptions
given.
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