Devon Bateman
ED 503 Dr. Holden
February 15, 2010
Position Paper: Teaching Stoichiometry
According to many researchers, including Dr. Musa Üce (2009), a professor at Marmara
University in Istanbul, Turkey, “abstract concepts are difficult to learn and this, in due course,
slows down the subsequent learning” (p. 684). Such is true in the understanding of
stoichiometry, the study of mass relationships in chemistry. Stoichiometry is universally one of
the most difficult topics in chemistry because it revolves around the conceptual understanding of
an abstract unit, the mole, a unit of measurement used to determine the amount of substances
consumed in a chemical reaction in addition to the amount of product formed. However, unlike
other units of measurement (meter, foot, gram), the mole is unique to the study of chemistry.
Prior to entering a chemistry class, students generally have no prior experience with the
mole and, therefore, lack the scaffolding needed to approach stoichiometric problems. Thus,
students rely on their teachers to introduce the topic and make stoichiometry relevant.
Traditional methods typically begin with the explanation of the four steps used to solve
stoichiometric problems: (1) write down the balanced chemical equation; (2) write down the
number of moles for each reactant and product; (3) calculate the molar masses; and (4) calculate
the unknown masses and volumes using a known one(s) (Haidar, 2008). While the steps are
valid and necessary to solve the word problems, the traditional teaching of stoichiometry falls
short of first providing students with a conceptual understanding of the mole as well as the other
units used in stoichiometry. In fact, Haidar (2008) and his team of researchers in the United
Arab Emirates have found that the teaching of this concept by traditional means in high school is
“limited at the algorithmic level of understanding” (p. 215). By introducing the four steps, then
giving examples showing how the rules are applied, and finally, asking students to solve similar
problems, teachers are asking their students to merely apply algorithms. Thus, when confronted
with new problems, novice chemistry students lack the metacognitive skills to ask the important
questions: “What am I doing? Why am I doing it? What do I already know about this topic?
What else needs to be done?” (Haidar, 2008, p. 216). Consequently, recent research has shown
difficulties in stoichiometry may be “due to the lack of abstract thinking and reasoning skills
rather than the lack of proficiency in math” (Üce, 2009, p. 684). Research has also shown that
conceptual teaching approaches, rather than traditional approaches, have significantly assisted
students in their understanding of the mole concept as well as other concepts in stoichiometry.
Dr. Üce (2009) and colleagues explain conceptual change as “being a process of learning
a concept starting from another concept. In chemistry, this process replaces chemical concepts
with relevant concepts and improves the understanding of the learned concepts” (p. 684). It is
important for teachers to first establish their students’ knowledge base. Then, rather than solving
practice problem after practice problem, teachers should first explore the concepts underlying the
problems and identify their relevance. From this solid foundation, problems which use the
concepts can be explored (Üce, 2009).
Several approaches were identified as helping to establish a conceptual understanding of
stoichiometry. First, Üce (2009) and colleagues demonstrated five steps which they feel should
be explored prior to solving stoichiometry problems. These steps are as follows:
Step 1: Students should define the term mole.
Step 2: Students should define the term atomic mass unit (amu).
Step 3: The relationship between Avogadro's number, atomic mass unit, and mass should
be explained.
Step 4: The relationship between molar mass and relative atomic mass should be
explained.
Step 5: The relationships between molar mass and relative atomic mass, and between
mole and atomic mass unit should be explained.
Moreover, Haidar (2008) and his team found that students should not only be asked to calculate
the masses of required substances as they are asked in traditional methods, but should also be
prompted to explain their calculations conceptually, in terms of the importance of the
coefficients that make up a balanced chemical equation (i.e. the mole concept) as well as the
relationship between the starting substances and the final products (i.e. the Law of Conservation
of Mass). Still other researchers have found the use of metaphors and flow diagrams to be
helpful conceptual techniques (Haidar, 2008). Finally, Marais (2009) and colleagues identified
structured worksheets used alongside tactile models, like Lego blocks, to be helpful tools for
students to “construct their own diagrammatic illustrations, and from there to interpret other
more generally used textbook representations of matter” (p. 95).
While there are numerous approaches to teaching stoichiometry, studies have shown that
a conceptual approach, rather than the traditional method, has significantly improved novice
students’ understanding of the topic. It is with this conceptual understanding that students are
equipped with the proper strategies of “planning, monitoring, revising and repairing
comprehension”, skills which can be applied throughout chemistry and across disciplines
(Haidar, 2008, p. 216).
Bibliography
Haidar, A.H., & Al Naqabi, A.K. (2008). Emiratii high school students’ understandings of
stoichiometry and the influence of metacognition on their understanding. Research in
Science & Technological Education, 26(2), 215–237.
Marais, F., & Combrinck, S. (2009). An approach to dealing with the difficulties undergraduate
chemistry students experience with stoichiometry. S. Afr. J. Chem., 62, 88–96.
Üce, M. (2009). Teaching the mole concept using a conceptual change method at college level.
Education, 129(4), 683-691.