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Inquiry-based dissolving
The National Science Education Standards and the AAAS Benchmarks both
promote an inquiry-based approach to
science education. When students inquire
about the world around them and engage
in scientific discovery, advanced concepts
are made accessible. The structure of
matter is a conceptually challenging topic
for middle school students. Therefore, it
is important to focus on inquiry-based instruction to make the content accessible.
In this way, a wide range of learners can
access the fundamental ideas.
This project highlights a dissolving unit
that was part of an eighth-grade, semesterStudents record their observations as they freely explore the materials provided.
long investigation into matter. During the
dissolving unit, students explored the
concepts of mixture, solution, dissolving, saturation,
well as a teaching method; the following are identified as
and conservation of mass. Dissolving is an advanced
characteristics of inquiry in the classroom:
concept that involves the atomic structure of matter and
the nature of chemical bonds. However, dissolving is also
• Scientifically oriented questions are used to engage
a common experience in students’ lives (e.g., when they
students in inquiry.
mix sugar in lemonade). The unit allowed students to
• Learners focus on finding evidence.
explore everyday materials in new ways, address common
• Learners use evidence to create explanations that admisconceptions, and pursue scientific discovery. In the
dress questions.
process, they were introduced to important chemistry
• Learners compare their explanations to alternative
concepts and developed a deeper understanding of the
explanations.
enduring understandings of physical science.
• Learners communicate their ideas and use evidence
to support their claims.
The inquiry process
Inquiry teaching and learning is both hands on and
minds on. It is hands on because it involves pursuing
experiments, manipulating materials, answering questions, and working cooperatively. It is minds on because
it requires active student thinking, problem solving,
analysis of information, and making meaningful connections to everyday life. Inquiry learning is in contrast
to traditional learning, which can be characterized as
passive learning where students listen, take notes, and
read. Inquiry is described in the National Science Education Standards (NRC 2000) as being a learning goal as
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Sometimes inquiry is misrepresented as unstructured
play with materials or hands-on experience without rigor.
However, when taught well, inquiry is a powerful tool in the
classroom. Inquiry teaching is a careful balance between
freedom and structure. As a teacher, you provide a space
for students to make decisions and to have ownership of
the process. You plan in advance the learning goals, focus
on what is most important, and provide scaffolding for the
learning experience. You create a learning environment
that allows students to uncover scientific phenomena and
construct their own understandings of science concepts.
Photos courtesy of the authors
by Gregory Benedis-Grab, Molly Petzoldt, and Lisbeth Uribe
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With careful planning and structure, students can be more
independent in investigating the world around them while
engaging in the powerful process of inquiry.
We hope the story of our approach to inquiry in an
eighth-grade chemistry class will provide an accessible
look at one example of inquiry teaching. We have presented
this unit under four headings that we used to structure the
inquiry process: prime the pump of inquiry, rework the
questions, pursue experiments, and critical thinking.
FIGURE 2
Probing questions that might
be posed to groups
• Why do you think that is happening?
• What do you think is causing that to happen?
• Have you noticed any difference when you add a substance to the hot water compared to the cold water?
• What do you think is causing it to be faster?
Prime the pump of inquiry
• What do you know about liquids at different
temperatures?
To kick off the study of dissolving, students were allowed
time to freely explore a variety of materials (see Figure 1)
before engaging in a formal experiment. The explorations primed their ideas around the concepts, ignited excitement about learning, and promoted the development
of questions. Some students have prior experience with,
and knowledge of, dissolving (such as when cooking),
thereby making the concept more relevant and accessible, whereas other students may need more time to experience dissolving for the first time. By giving all students
a chance to manipulate the materials, we are leveling the
playing field, so that all students have sufficient experience from which researchable questions can be drawn.
Choosing the right materials for the investigation is
critical. We chose these materials to focus the student
investigations on our learning goals, specifically on the
process of dissolving, saturation, conservation of matter,
and the rate of dissolving. Though the range of materials
provided to students was purposely limited to help focus
the exploration, there was also variety to allow for creativity
and discovery. The solids and liquids used were chosen
because they are familiar household items and this
familiarity made the scientific concepts under investigation
less abstract and foreign. We chose these materials because
• Could that help you to explain what you are observing?
• What do you know about oil and water?
• Could that help you to explain what you are observing?
of their different rates of dissolving. It was also important
that solubility could be achieved by varying the substances
chosen, the temperature, and the grain size.
While working with the materials for the first time,
students were asked to see what they could discover
about the materials and to write questions about their
observations in their lab journals. They creatively used
the materials and made many discoveries. One group
poured some sugar into the water, exclaiming, “Look.
Some of the sugar is at the bottom of the beaker.” Another
student commented, “I think if we stir it, the sugar will
dissolve. Let’s try.” Meanwhile, the teacher circulated
the room, listening carefully to groups that progressed
independently and helping those that needed direction
(Figure 2). Below is an example of a dialogue between
teacher and students.
Solids
Teacher: What do you notice happening?
Student 1: Watch. The sugar is disappearing.
Teacher: How do you know it disappeared?
Student 1: It’s gone.
Student 2: It’s dissolving.
Teacher: What do you mean when you say dissolving?
Student 2:: They mix together.
Teacher: Earlier, you said that the sugar was gone. Can
you think of a way that we could test if the water and
sugar have mixed together or if the sugar is gone?
Try to write that down as one of our questions.
Confectioners’ sugar, granulated sugar, salt, cocoa
powder, sand, flour, corn starch
Rework questions
FIGURE 1
Instructions for beginning the
inquiry experience
Students were given time to freely work at their tables with
the following materials:
Tools
Balances, petri dishes, test tubes and racks, graduated
cylinders, beakers, hot plates
Liquids
Hot and cold water, oil, alcohol, dish soap
After 20 to 30 minutes, we asked students to leave their
materials at the lab tables and join us at the front of the
room for a group discussion. As students shared their
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questions with the class (Figure 3), we wrote them on
the board. Once five questions were volunteered, we discussed the questions in order to determine which questions could be answered with an experiment. We said to
the class, “All of these are good questions, but some of
them are easier to turn into experiments than others.
Which of these are good experimental questions?”
During the ensuing discussion, students debated why
certain questions are answerable through experimentation
and others are not. It was agreed that questions such as
“Why does the salt not dissolve in alcohol?” could not be
easily answered through an experiment. Instead, some of
the questions needed to be modified to become experimental
questions, such as “What is the saturation point of salt in
different solvents?” Terms such as solvent and solute were
introduced at this point to give more specificity to the
discussion. Similarly, yes/no questions can be adjusted to
lead to more complex inquiry. For example, the question
“Does salt dissolve in water?” could be modified to “How
much salt can completely dissolve in 500 mL of water?”
Defining variables is an excellent way to help
students analyze their questions and develop appropriate
investigations. Incorporating the concept of variables
into the experiment design is a gradual process. Some
students are familiar with variables while others are not.
Even the experienced student needs the opportunity
to work with and build upon their understanding of
variables. We introduced students to variables while
they were designing their experiment by asking probing
questions such as “What are you trying to find out? If you
are changing both the temperature and the solvent, how
will you know which is causing the change? If you kept
one thing the same throughout the entire experiment,
what would that tell you?” The purpose of our questions
was to serve as a reminder for students who already
had a foundational understanding of variables and as an
introduction to the concept of manipulating variables for
those who were not exposed to it previously.
However, variables can be referred back to later in the
inquiry process. When students present their findings
to the class, their peers often catch their mistakes in
having too many variables. Students also have a difficult
time making a strong claim because of having so many
variables. By revisiting variables at multiple times in the
inquiry process, students were able to construct a deeper
understanding of how to use them in inquiry.
Pursue experiments
Next, groups of students chose a research question upon
which to focus during the inquiry. They either reworked a
question from their initial inquiry or chose a question sug-
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FIGURE 3
Student-generated questions
• How does the temperature affect how much sugar
dissolves in a solvent?
• If you make a mixture of alcohol and water, how
does the ratio of the two liquids affect the amount of
salt that dissolves in the mixture?
• Is there a relationship between the amount of water
used and the amount of substance that will fully dissolve in the water?
gested by another group. They wrote the purpose, procedure, and materials sections in their lab journal and drew a
table to record their observations (Figure 4). After receiving teacher approval, they gathered their materials and
began their investigation. One group wanted to test for the
conservation of mass. They measured 5 g of salt and added
it to 50 g of water. They then determined that the new mass
was 58 g. They were surprised, as shown in the following
dialogue.
Student 1: I wonder why it does not add up? I thought
that mass does not change.
Student 2: Maybe mass is not conserved.
Teacher: What might be a benefit of doing the experiment multiple times?
Student 1: We could see if we get the same answer.
Then we can be more sure.
Students did two more trials and determined a final
mass of 55 g and 54.9 g, respectively.
Student 1: The last two answers are closer. Maybe we
made a mistake the first time?
Student 2: Let’s try it one more time and see what we get.
Later they measured the volume of the solute, the
volume of the solvent, and then the volume of the solution.
There was a much larger difference this time.
Student 1: Look, there is a difference of 4 mL. I guess
volume is not conserved.
Student 2: I wonder if that is why the density of the salt
water is different because the volume is changing?
Student 1: Let’s try it again to see if we get the same
results.
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FIGURE 4
Notes from student lab book documenting experiment on how the rate of dissolving is
affected by type of sugar used.
Another group was interested in finding out how the
temperature of the solvent affected the amount of sugar
that could be dissolved. They put 100 mL of water on a
hot plate for different amounts of time and then tested
the saturation point for each trial.
Student 1: Look! The more time we put it on the hot
plate, the more sugar dissolves.
Student 2: We could make a graph of this.
Teacher: What would go on the x-axis of the graph?
Student 1: Minutes on the hot plate.
Teacher: That is right. But, I wonder if there is a more
accurate way to measure how hot the water is?
Student 2: Oh, we could use a thermometer. That would
be more accurate.
During this phase of inquiry, there needs to be enough
time for students to work independently and complete
their experiments. We gave students two and a half
hours to complete their experiments. Although it takes
significant time, students become independent in their
learning and have ownership over their discoveries. The
teacher can help keep all the groups focused through
guidance and also targeting specific science process
skills for particular students.
Critical thinking:
Share results/discuss connections
At the conclusion of the experiment, the groups shared
their findings with the class. There are many ways to
share findings, and it is important to expose students to
different styles of presentation. In this case, we had each
group display a graph of their findings and share their
analysis with the class.
One group had found the saturation point for salt
in a mixture of alcohol and water. They compared the
saturation point for different ratios of water to alcohol.
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Their graph showed an increase in the saturation
point as the percentage of water increased in the
mixture. Students shared, “We think that alcohol
is not so good at dissolving salt because the more
alcohol, the less salt dissolves.” Another group
compared the rate of dissolving for different
types of sugar. They timed how long it took
confectioners’ sugar and granulated sugar to
dissolve in a set amount of water. During their
presentation, the student stated, “We found that
the confectioners’ sugar dissolved faster. That
sort of makes sense because it is so small it can go
into the water faster.” Students asked questions
about each presentation. The teachers also asked
questions of the presenters and then the class.
For example, we asked, “Why do you think the
salt would dissolve in water and not in alcohol?
Who thinks they can explain why small particles
might dissolve faster than larger particles?”
After allowing students to express their ideas,
we presented scientific content that related Students record change in volume and mass as they add set amounts of
directly to their experiments. We showed a salt to water.
diagram of the polar configuration of H2O and
related that to how salt dissolves in water.
It is an effective teaching method because students are moAlcohol, which does not have the same strong polar
tivated by their own creativity and desire to discover. Stuconfiguration, does not dissolve salt effectively.
dents learn how to think critically and communicate their
We also showed a diagram of cubes that illustrated
ideas as they become more comfortable with inquiry.
the relationship between volume and surface area. This
The inquir y process is even more beneficial if it
helped explain why small particle sizes will dissolve faster
is revisited throughout the year. The skills can be
than larger ones. In this way, students are able to rethink
introduced, applied, and eventually mastered as students
their prior ideas and develop a richer understanding of
repeat the inquiry process over and over again. Students
the concepts.
become confident at experimenting independently and
We led a discussion on whether mass is conserved and
learn to pursue scientific knowledge on their own.
used data from one of the experiments to push student
thinking on this concept. We then encouraged students
References
to use a particulate model of matter to justify that mass is
NRC (National Research Council). 2000. Inquiry and the
conserved. If you have the same number of molecules before
national science education standards: A guide for
and after dissolving, then the mass must be the same.
teaching and learning. Washington, DC: National Academies Press.
Conclusion
As students moved through the inquiry process, they constructed their understanding of the scientific concepts.
Students are motivated to do science when their creative
ideas are put into action through designing and conducting their own experiments. Many lab activities do not allow students to experience the creative side of science in
terms of developing experiments. Particularly in chemistry, students are often asked to follow a set procedure and
reflect on “what happened.” The inquiry process fosters
excitement while also creating the important connection
between scientific practices and scientific understanding.
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Gregory Benedis-Grab (gbenedisgrab@theschool.
columbia.edu) is a K–8 science teacher at the
School at Columbia University and an adjunct
instructor at Bank Street College Graduate School
of Education in New York City, New York. Lisbeth
Uribe is a K–8 science teacher at the School at
Columbia University in New York City, New York.
Molly Petzoldt is a middle school science teacher
at Packer Collegiate Institute in Brooklyn Heights,
New York.
Photos courtesy of the authors
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