Side NoteFound that having students engage in explanation changes or refines their image of science as well as enhances their understanding of the nature of science (Bell & Linn, 2000). Third, onstructing explanations can enhance the students’ understandings of the

SCIENTIFIC EXPLANATION

Why Scientific Explanations?Science education reform efforts call for students to

develop scientific processes and skills through inquiry

(American Association for the Advancement of Science,

1993; National Research Council, 1996). One prominent

inquiry practice in both the standards documents and

research literature is the construction, analysis, and

communication of scientific explanations. We believe that

explanation construction should be an important part of

science class for three reasons. First, research into

scientists’ practices portrays a picture where scientists

construct arguments or explanations including weighing

evidence, interpreting text, and evaluating claims (Driver, Newton, & Osborne, 2000).

Second, previous research in science education has found that having students engage in

explanation changes or refines their image of science as well as enhances their

understanding of the nature of science (Bell & Linn, 2000). Third, constructing explanations

can enhance the students’ understandings of the science content (Driver, Newton &

Osborne, 2000). A deep understanding of science content is characterized by the ability to

explain phenomena (Barron et. al. 1998). Consequently, evaluating students’ explanations

can also provide teachers with an opportunity to assess students’ current understanding.

Although explanations are often cited as important for classroom science, they are

frequently left out of classroom practice (Kuhn, 1993; Newton, 1999). One of our goals in

creating this unit was to make students’ explanation construction an important part of the

instructional sequence. Previous research has found that making scientific thinking

strategies, like explanation, explicit to students can facilitate students’ use and

understanding of these strategies (Herrenkohl, Palinscar, DeWater, & Kawasaki, 1999; Toth,

Klahr& Chen, 2000). One of the ways we hope to help students with explanations is by

making the conventions (behind explanations and the reasons why explanations are

important) clear to students. We do this when we first introduce students to explanations

(Lesson 6). We then continue to support students’ writing of explanations through supports

in both the activity sheets and student reader. Furthermore, we provide suggestions to the

teacher about difficulties that students might have as well as ways to support students with

the construction of explanations.

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What is a Scientific Explanation?A scientific explanation is a written or oral response to a question that requires students to

analyze data and interpret that data with regard to scientific knowledge. Our explanation

framework includes three components: claim, evidence, and reasoning. While we break

down explanations into these three components for students, our ultimate goal is to help

students to create a cohesive explanation in which all three components are linked together.

Yet we have found that first breaking explanations down into the three components can

ultimately help students create cohesive explanations. In the following section, we describe

the three components of a scientific explanation as well as provide an example of one

student’s explanation to illustrate the different components.

Student ExampleQuestion: “Write a scientific explanation stating whether you think fat and soap are the

same substance or different substances.”

Student response: “Fat and soap are different substances. Hardness was different for fat

and soap. Also, fat dissolves in oil, soap does not dissolve in oil. The fat melts at 24 C and

soap melts at way above 100 C. Fat and soap are both white. Even though they are the

same colors, they are different substances because they have a lot of other different

properties. Different substances have different properties.”

ClaimThe claim is a testable statement or conclusion that answers the original question. For

instance, in the student example above the claim is “Fat and soap are different substances.”

The claim is the simplest part of an explanation and often the part students’ find the easiest

to include as well as to identify when they are critiquing other peoples’ explanations. One of

the purposes in focusing on scientific explanations is to help students include more than a

claim in their writing.

EvidenceThe evidence is scientific data that supports the student’s claim. This data can come from an

investigation that students complete or from another source, such as observations, reading

material, archived data, or other sources of information. Depending on the claim being

made, this data can be qualitative or quantitative. In the student example above, the

evidence comes from investigations the student conducted, “Hardness was different for fat

and soap. Also, fat dissolves in oil, soap does not dissolve in oil. The fat melts at 24 C and

soap melts at way above 100 C. Fat and soap are both white.”

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The data needs to be both appropriate and sufficient to support the claim. When introducing

evidence to middle school students, we suggest discussing appropriate data in terms of

whether the data supports the claim. For this question, using the data that soap is used to

wash clothes while fat is used to cook is not appropriate data because students learn in the

unit that properties are used to determine whether two objects are the same or different

substances. Consequently, it is also not appropriate to include “volume” or “mass” as

evidence, even though they are scientific data. This is because volume and mass are not

properties so they cannot be used to compare substances. A good explanation only uses

data that supports the claim in answer to the original question. In this example, students

need to use properties, like melting point or solubility, to support their claim.

Students should also consider whether or not they have sufficient data. When introducing

this concept to middle school students, we suggest discussing sufficient data in terms of

whether they have enough data. During the unit, students learn that using one property will

not necessarily tell them if two objects are different substances. For instance, two

substances might be soluble in water. This is not enough evidence to tell if the substances

are the same or different. Instead, students need to include a number of properties to

support their claim.

When students are selecting their data to use as evidence, they should consider both

whether it is appropriate to support their claim and whether they have enough data to

support their claim. We have found that this can be difficult for students. While they realize

that they should include data as evidence, they are not necessarily sure which data to use or

how much data to use.

ReasoningReasoning is a justification that shows why the data counts as evidence to support the claim

and includes appropriate scientific principles. The reasoning ties in the scientific background

knowledge or scientific theory that justifies making the claim and choosing the appropriate

evidence. In the student example above, the reasoning statement is “…they are different

substances because have a lot of other different properties. Different substances have

different properties.” This statement tells why the student used color, hardness, solubility

and melting point as evidence (i.e. they are properties) and includes the scientific theory

that different substances have different properties to justify using the evidence to support

the claim.

We have found that students have a difficult time including the entire reasoning component

in scientific explanations. Often students simply make a general link between the claim and

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evidence. For example, students may say, “Since fat and soap have different densities and

melting points, they are different substances.” In this example, the reasoning supporting the

link between claim and evidence is not explicit. You want to help students learn to include

the scientific background knowledge that allowed them to make that connection between

claim and evidence. They should include the scientific principles that different substances

have different properties.

How To Support Students’ Constructionof Scientific ExplanationsMany middle school children will find constructing scientific explanations as difficult. It is not

an inquiry skill that they can learn quickly. Students need support in terms of when, how,

and why to use the claim/evidence/reasoning framework. We suggest using a number of

techniques during the unit to help students with this new inquiry process. Some of these

techniques are embedded in the curriculum materials. We also encourage you to use them

during classroom discussions in order to make explanation an important component of

everyday classroom practice.

1. Make the framework explicit. You want to help students understand the three

components of explanations. They should understand what these three components

are as well as the definitions of the three components.

2. Model the construction of explanations. After introducing explanations, you

want to model how to construct explanations through your own talking and writing.

When it is appropriate, provide students with examples of explanations. Furthermore,

identify for students where the claim, evidence, and reasoning were in your own

example.

3. Encourage students to use explanations in their responses. During class

discussions, if a student makes a claim ask them to provide an explanation for that

claim. Encourage students to provide evidence and reasoning to support their claims.

4. Have students critique explanations. When students write explanations in class,

you may want to have them trade their explanations with a neighbor and critique

each other’s explanations. Focus students’ attention on discussing both the strengths

and weaknesses of their partners’ explanations and offering concrete suggestions for

improvement. Instead, you may want to show students an overhead of a generic

student’s response and as a class critique the explanation. Or you may want to

provide students with an example of a scientific explanation from a newspaper,

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magazine or website. Then you could have students critique the explanation in terms

of the claim, evidence, and reasoning.

5. Provide students with feedback. When students construct explanations,

comment on their explanation as a whole as well as the quality of the individual

components. You may want to coach them on how to improve their explanations by

asking them leading questions or providing them with examples. For example, you

may want to ask students what the reasoning was in their explanation and how they

might improve their reasoning.

While supporting students’ construction of scientific explanations can be a time-consuming

process, there are numerous benefits. Helping students understand and be able to construct

explanations can result in a greater understanding of science content and science as an

inquiry process.

References

American Association for the Advancement of Science. (1993). Benchmarks for science literacy. New York: Oxford University Press.

Barron, B., Schwartz, D., Vye, N., Moore, A., Petrosino, A., Zech, L., Bransford, J., & The Cognition and Technology Group at Vanderbilt. (1998). Doing with understanding: lessons from research on problem- and project-based learning. The Journal of the Learning Sciences. 7 (3&4), 271-311.

Bell, P., & Linn, M. (2000). Scientific arguments as learning artifacts: Designing for learning from the web with KIE. International Journal of Science Education. 22 (8), 797-817.

Driver, R., Newton, P. & Osborne, J. (2000). Establishing the norms of scientific argumentation in classrooms. Science Education. 84 (3), 287-312.

Herrenkohl, L. R., Palinscar, A. S., DeWater, L. S., & Kawasaki, K. (1999). Developing Scientific Communities in Classrooms: A Sociocognitive Approach. The Journal of the Learning Sciences. 8(3&4), 451-493.

Kuhn, D. (1993) Science as argument: Implications for teaching and learning scientific thinking. Science Education, 77, 319-338.

National Research Council. (1996). National Science Education Standards. Washington, DC: National Academy Press.

Newton, Paul. (1999). The Place of Argumentation in the Pedagogy of School Science. International Journal of Science Education, 21 (5), 553-576

Toth, E. E., Klahr, D., Chen, Z. (2000). "Bridging research and practice: A cognitively based classroom intervention for teaching experimentation skills to elementary school children." Cognition & Instruction 18(4): 423-4

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Samples of student work – explanationWrite a scientific explanation stating whether these are the same or different substances.

Properties

Color Hardness SolubilityMelting Point

Density

Fat

Off white

or

Slightly

yellow

Soft

Squishy

Water – No

Oil – Yes47 C 0.92 g/cm3

Soap Milky white HardWater – Yes

Oil – No

Higher than

100C0.84 g/cm3

Quality Example:

Fat and soap are different substances (correct claim). Fat is off white and ivory is milky white.

Fat is soft squishy and soap is hard. Fat is soluble in oil, but soap is not soluble in oil. Soap is

soluble in water, but fat is not. Fat has a melting point of 47 C and soap has a melting point

above 100 C. Fat has a density of 0.92 g/cm3 and soap has a density of 0.84 g/cm3 (correct

evidence). These are all properties. Because fat and soap have different properties, I know

they are different substances. Different substances always have different properties (correct

reasoning).

Examine the following data table:

Density Color Mass Melting Point

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Liquid 1 0.93 g/cm3 no color 38 g -98 C

Liquid 2 0.79 g/cm3 no color 38 g 26 C

Liquid 3 13.6 g/cm3 silver 21 g -39 C

Liquid 4 0.93 g/cm3 no color 16 g -98 C

Write a scientific explanation that states whether any of the liquids are the same

substance.

Example 1 :

Example 2:

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© 2008, University of Michigan