Content Benchmark P.8.A.8
Students know substances containing only one kind of atom are elements which cannot be broken
into smaller pieces by normal laboratory processes. E/S
Philosophers have long expressed differing ideas about the nature of matter. Even ancient
cultures had developed elaborate beliefs about the origin and nature of matter (for example, the
Greek idea that all things are made up of some combination of fire, water, air, and earth).
Understanding the nature of elements seems easily comprehensible, but students often struggle
with the concept that atoms are not divisible under ordinary laboratory conditions.
Figure 1. The Four Elements of Western Alchemy.
The figures shows how the four elements were imagined to combine in
various pairs to produce the "qualities" of hot, cold, wetness and dryness.
(From http://www.chem1.com/acad/webtext/intro/AT.html)
To learn more about the classic elements and how they contributed to the development of
chemistry, go to http://web.lemoyne.edu/~giunta/EA/CONTENTS.HTML.
Alchemists had begun experimenting with metals, ores, and other substances in their attempts to
make precious metals and materials. They knew through their experimentation that substances
could be broken down into simpler substance, but at some point those substances could not be
further simplified. Most of the common elements had not been identified until the technology
existed to decompose naturally occurring compounds. Seven elements that had been known since
antiquity are shown below.
Fe
Ferrum
Cu
Ag
Sn
Au
Cuprum
Argentum
Stannum
Aurum
Hg
Pb
Hydrargyrum Plumbum
Figure 2. Seven Elements Known Since Antiquity
(From http://www.vanderkrogt.net/elements/fecu.html)
To help students understand the basic nature of elements, it may be helpful to review John
Dalton’s Atomic Theory, which included ideas that were revolutionary in his time.
1. Matter is neither created nor destroyed in chemical reactions. In other words, in
ordinary chemical reactions, atoms are rearranged but never destroyed. To learn more
about the conservation of mass, please go to MS TIPS Benchmark P.8.A.5.
2. Compounds are composed of a definite number of atoms in a specific ratio. The
masses of each of the elements in a compound are always the same. Elements in a
compound are always present in the same proportions by mass. To learn more about
compounds, please go to MS TIPS Benchmark P.8.A.4.
3. Elements may combine with each other in different ratios to make different
compounds but the differences in mass are always whole number differences. To
learn more the relationships among compounds, please go to MS TIPS Benchmark
P.8.A.4.
Dalton understood that atoms could not be further subdivided in ordinary chemical reactions. His
theory helped chemists organize their understandings of matter. The concept map below provides
a road map for students beginning their studies of atoms, elements, compounds and their
characteristics.
Figure 3. Concept Map of Elements
(From http://www.chem1.com/acad/webtext/intro/AT.html)
Further readings about the history of elements can be found at
http://www.chem1.com/acad/webtext/intro/AT.html.
Elements are substances composed of one type of atom containing a specific number of protons.
Henry Moseley (1887-1915) identified the atomic number of an element as the fingerprint of an
element. This idea was revolutionary and provided support for Dalton’s Atomic Theory. As a
result the idea emerged that all atoms of an element contain the same number of protons. Atoms
interact with each other in chemical reactions by transferring electrons. In this way, new
compounds are formed.
It may be helpful to use some different models to help students understand this concept. M&M’s
of one color could be used to demonstrate atoms of an element, but the analogy is limited and
students should be queried as to the strengths and weaknesses of the model. Another analogy that
could be used is a bag of sticky white marshmallows where each marshmallow represents an
atom of an element, but the stickiness helps keep them bound together in the element; again,
students should be queried for the strengths and limitations of the model. Finally, students could
be prompted to make paper models of atoms of different elements writing the number of protons
in the center of their model. Students should identify why their models effectively represent
atoms of an element and should demonstrate through manipulation of their models how chemical
reactions form new substances.
Content Benchmark P.8.A.8
Students know substances containing only one kind of atom are elements which cannot be broken
into smaller pieces by normal laboratory processes. E/S
Common misconceptions associated with this benchmark
1. Students incorrectly think that the Law of Conservation of Mass does not apply to
atoms.
Students may be able to repeat the Law of Conservation of Mass, but see no problem with atoms
disappearing or appearing to balance equations. Conceptually students understand the idea of
balancing equations, but when asked to write equations, they systematically remove or add atoms
revealing their misconception. One of the best ways to address this misconception is to have
students use models (manipulatives) to account for atoms on both the reactant and product sides
of the equation.
To learn more about this misconception and other science misconceptions, go to
http://www.middleschoolscience.com/balance.html.
2. Students incorrectly assume that elements can form other elements.
Several students when questioned about the appearance of copper on magnesium ribbon in
copper sulfate remarked that the brown solid came from the magnesium. They thought it was
somehow present in the magnesium even though they agreed that magnesium was an element.
Using online demonstrations or videos demonstrating reactions will assist helping students gain
experience with this concept. Major difficulties in this misconception reside in student
inexperience with chemical reactions. Showing the demonstration and having students explain
using scientific evidence will bolster their understandings.
To learn more about this misconception and other science misconceptions, go to
http://apps.exploratorium.edu/10cool/index.php?cmd=browse&category=4.
3. Students incorrectly using representations of elements can lead to misconceptions.
Students cannot easily visualize atoms of an element. Teachers need to be cognizant that models
and pictures can lead to alternative ideas about the structure of matter. Figure 4, shown below,
represents one way to assist students in developing abstract ideas about chemical reactions.
To learn more about this misconception and other science misconceptions, go to
http://intro.chem.okstate.edu/ChemSource/ChemRx/chemrx11.htm.
Figure 4. Pictures in the Mind.
(From http://intro.chem.okstate.edu/ChemSource/ChemRx/chemrx11.htm)
Content Benchmark P.8.A.8
Students know substances containing only one kind of atom are elements which cannot be broken
into smaller pieces by normal laboratory processes. E/S
Sample Test Questions
Questions and Answers to follow on separate document
Content Benchmark P.8.A.8
Students know substances containing only one kind of atom are elements which cannot be broken
into smaller pieces by normal laboratory processes. E/S
Answers to Sample Test Questions
Questions and Answers to follow on separate document
Content Benchmark P.8.A.8
Students know substances containing only one kind of atom are elements which cannot be broken
into smaller pieces by normal laboratory processes. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Chemical Reactions with Flash Animation
This site has a series of student developed animations that can assist students in understanding
the basic types of chemical reactions. Students are able to view the animation as well as see the
balanced chemical reactions. The teacher can help students understand that compounds rearrange
their atoms to form different compounds, but can also decompose into its component elements.
Please note that Flash™ will need to be installed on the computers for students to use this site.
To access these activities, go to
http://www.marymount.k12.ny.us/marynet/stwbwk05/05hchemistry.html.
2. Learning to Read Chemical Equations
This site provides an activity with template to help students read chemical equations by
identifying their elements and counting the numbers of atoms of an element. Although the
Nevada State Science Standards do not specify that middle school students be able to balance
equations, it is helpful for students to be able to identify the reactants and products and their
respective coefficients. This site will assist students in this process.
To access these activities, go to http://www.middleschoolscience.com/balance.html.
3. Classic Chembalancer
This site is for more advanced students who want to practice balancing equations. The interactive
game lets students use the Law of Conservation of Mass to balance the compounds and elements
in the equations.
To access these activities, go to
http://funbasedlearning.com/chemistry/chembalancer/default.htm.
More challenging equations can be found at
http://funbasedlearning.com/chemistry/chembalancer3/ques2.htm.
4. Cartoon Chemistry
This is a site that provides a worksheet which visually helps middle school students understand
different types of chemical reactions that occur. Students get the idea that elements cannot be
broken down but through reactions form new substances with new characteristics.
To access these activities, go to
http://www.nclark.net/CartoonChemistry.doc.
5. Chemistry of Fireworks
Nova developed this site which asks students to consider the relationship between the
electromagnetic spectrum and the atomic structure of an atom of an element. The discussion is
helpful for students in the understanding that atoms of elements have their own characteristic
spectrum and that when heated they produce the characteristic spectrum.
To access these activities, go to
http://www.teachersdomain.org/resources/phy03/sci/phys/matter/fireworkcol/index.html.