Research Matters  to the Science
Teacher
Problem Solving in Chemistry
by Dorothy Gabel
One of the major difficulties in teaching introductory chemistry
courses is helping students become efficient problem solvers. Most
beginning chemistry students find this one of the most difficulty
aspects of the introductory chemistry course. What does research tell
us about problem solving in chemistry? Just why do students have such
difficulty in solving chemistry problems? Are some ways of teaching
students to solve problems more effective than others?
Problem solving in any area is a very complex process. It involves an
understanding of the language in which the problem is stated, the
interpretation of what is given in the problem and what is sought, an
understanding of the science concepts involved in the solution, and
the ability to perform mathematical operations if these are involved
in the problem.
The first requirement for successful problem solving is that the
problem solver understand the meaning of the problem. In order to do
so there must be an understanding of the vocabulary and its usage in
the problem. There are two types of words that occur in problems,
ordinary words that science teachers generally assume that students
know and more technical terms that require understanding of concepts
specific to the discipline. Researchers have found that many students
do not know the meaning of common words such as contrast, displace,
diversity, factor, fundamental, incident, negligible, relevant,
relative, spontaneous and valid.
Slight changes in the way a problem is worded may make a difference
in whether a students is able to solve it correctly. For example,
when "least" is changed to "most" in a problem, the percentage
getting the question correct may increase by 25%. Similar
improvements occur for changing negative to positive forms, for
rewording long and complex questions, and for changing from the
passive to the active voice. Although teachers would like students to
solve problems in whatever way they are framed they must be cognizant
of the fact that these subtle changes will make a difference in
students' success in solving problems.
From several research studies on problem solving in chemistry, it is
clear that the major reason why students are unable to solve problems
is that they do not understand the concepts on which the problems are
based. Studies that compare the procedures used by students who are
inexperienced in solving problems with experts show that experts were
able to retrieve relevant concepts more readily from their long term
memory. Studies have also shown that experts concepts are linked to
one another in a network. Experts spend a considerable period of time
planning the strategy that will be used to solve the problem whereas
novices jump right in using a formula or trying to apply an
algorithm.
In the past few years, science educators have been trying to
determine which science concepts students understand and which they
do not. Because chemistry is concerned with the nature of matter, and
matter is defined as anything that has mass and volume, students must
understand these concepts to be successful problem solvers in
chemistry. Research studies have shown that a surprising number of
high school students do not understand the meaning of mass, volume,
heat, temperature and changes of state. One reason why students do
not understand these concepts is because when they have been taught
in the classroom, they have not been presented in a variety of
contexts. Often the instruction has been verbal and formal. This will
be minimally effective if students have not had the concrete
experiences. Hence, misconceptions arise.
Although the very word "misconception" has a negative connotation,
this information is important for chemistry teachers. They are
frameworks by which the students view the world around them. If a
teacher understands these frameworks, then instruction can be
formulated that builds on student's existing knowledge. It appears
that students build conceptual frameworks as they try to make sense
out of their surroundings.
In addition to the fundamental properties of matter mentioned above,
there are other concepts that are critical to chemical calculations.
One of these is the mole concept and another is the particulate
nature of matter. There is mounting evidence that many students do
not understand either of these concepts sufficiently well to use them
in problem solving. It appears that if chemistry problem solving
skills of students are to improve, chemistry teachers will need to
spend a much greater period of time on concept acquisition. One way
to do this will be to present concepts in a variety of contexts,
using handson activities.
What does this research imply about procedures that are useful for
helping students become more successful at problem solving?
Chemistry problems can be solved using a variety of techniques.
Many chemistry teachers and most introductory chemistry texts
illustrate problem solutions using the factorlabel method. It has
been shown that this is not the best technique for high school
students of high mathematics anxiety and low proportional reasoning
ability. The use of analogies and schematic diagrams results in
higher achievement on problems involving moles, stoichiometry, and
molarity.
The use of analogs is not profitable for certain types of problems.
When problems became complex (such as in dilution problems) students
are unable to solve even the analog problems. For these types of
problems, using analogs in instruction would be useless unless
teachers are willing to spend additional time teaching students how
to solve problems using the analog.
Many students are unable to match analogs with the chemistry problems
even after practice in using analogs. Students need considerable
practice if analogs are used in instruction.
When teaching chemistry by the lecture method, concept development
needed for problem solving may be enhanced by pausing for a two
minute interval at about 8 to 12 minute intervals during the lecture.
This provides students time to review what has been presented, fill
in the gaps, and interpret the information for others, and thus learn
it themselves.
The use of concept maps may also help students understand concepts
and to relate them to one another.
Requiring students to use a worksheet with each problem may help them
solve them in a more effective way. The worksheet might include a
place for them to plan a problem, that is list what is given and what
is sought; to describe the problem situation by writing down other
concepts they retrieve from memory (the use of a picture may
integrate these); to find the mathematical solution; and to appraise
their results.
Although the research findings are not definitive, the above
approaches offer some promise that students' problem solving skills
can be improved and that they can learn to solve problems in a
meaningful way.
For further information about this research area, please
contact:
Dr. Dorothy Gabel
Education Building
3rd and Jordan
Bloomington, Indiana 47405
Research Matters  to the Science Teacher
is a publication of the National Association
for Research in Science Teaching
