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Nature of Science

Performance Benchmark N.8.A.6
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Nature of Science
Scientific Inquiry




Science, Technology, and Society
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know scientific inquiry includes evaluating results of scientific investigations, experiments, observations, theoretical and mathematical models, and explanations proposed by other scientists.  E/S

Scientific Inquiry
Every branch of science includes facts, models, theories, and laws. The soundness of these scientific models, theories, and laws is based on their usefulness in making predictions of natural events and processes.  Scientific inquiry is the process underlying our advances in knowledge and understanding.  The most basic form of scientific inquiry begins with a question that is based on observations of an event or process. Through scientific inquiry students develop the ability to ask questions about the world around them, think of ways to answer those questions, choose or form hypotheses, and construct experiments to test those hypotheses. The table below summarizes many of the skills students acquire through the use of the process of scientific inquiry.

Skills developed through the process of scientific inquiry

Classifying and sequencing




Predicting and hypothesizing

Communicating effectively

Constructing and interpreting models

Defining, controlling, and manipulating variables in experiments

Analyzing, interpreting and evaluating data

Drawing conclusions and justifying them

With repeated experience middle school students can become very adept at the use of a high level of scientific inquiry. Early in the training process inquiry experiences are generally very structured by the teacher. One particular investigative process might be the focal point such as identifying a problem or question for investigation, or learning to design good procedures.

The next, logical step toward independent scientific inquiry is guided inquiry in which students are given the responsibility of investigating a problem presented by the teacher. Guided inquiry is an essential experience for students as they move toward becoming proficient in thinking about and participating in the process of scientific investigation.

The pinnacle of true scientific inquiry in the classroom is reached when students have learned to identify their own scientific questions or problems to investigate. At this level of inquiry students have the experience and confidence necessary to design and conduct an entire scientific investigation

Figure 1 shows the inquiry continuum Northwestern University outlines in their Materials World Modules.

Figure 1. The Inquiry Continuum.

The Materials World Modules are an “Inquiry and Design-Based Science, Technology, Engineering, and Mathematics (STEM) Educational Program.” For more information about this program visit the Northwestern University website at

Although the process of scientific inquiry can be messy, noisy, and fraught with errors and problems, students engaged in true scientific inquiry can and do learn to think in terms of scientific process.  The ultimate goal in the process is for students to be able to construct meaning from their investigations and to be able to make connections to how things work in everyday life in the world outside of the classroom.

For a complete and concise analysis of the process of scientific inquiry in the classroom, including teaching strategies, inquiry scoring guides, and resources visit The Northwest Regional Education Academy’s website at

Experimental Design
The process of scientific inquiry cannot be defined narrowly as occurring in one specific format; however the following review of the key elements of the investigative process serves as a general guide. Each step of the process is defined and includes an explanation of how it could be presented.

Identifying a Problem
The problem should be written in the form of a question that cannot be answered with a yes or a no. The question must be testable through the process of investigation and should identify the independent and dependent variables. For example, “How does increasing the mass in grams on a cart (independent variable) affect the amount of force in Newtons (dependent variable) it takes to move the cart?

A hypothesis should be stated as a prediction of the affect of the independent variable on the dependent variable. For example, “If the mass on a cart (independent variable) is increased, then the amount of force (dependent variable) needed to move the cart will increase.”

For a guide on the nature of hypotheses and how to correctly write a hypothesis visit the “What is a Hypothesis?” website at

Variables are any factor that could affect the results of an experiment and are separated into the independent variable, the dependent variable, and variables to be held constant (often called controlled variables.)

  • Independent variable: The independent variable is often called the cause variable or the experimental variable. The independent variable is manipulated or changed during an investigation in order to determine its impact on the dependent variable.
  • Dependent variable: The dependent variable is often called the effect variable or the responding variable. The dependent variable is measured as it responds to changes in the independent variable during an investigation.
  • Constants: The variables to be held constant in an experiment are often also called controlled variables. Since the purpose of an investigation is to determine the affect of the independent variable on the dependent variable, all other variables that could impact the results of the investigation must be held constant. For example, in the investigation of the question about how increasing mass will affect the force needed to move a cart some variables that should be held constant might include using the same cart, measuring force in the same way, and moving the cart over the same surface for each trial.

Controls can be introduced in classroom experiments as the standard for comparison of the impact of the independent variable on the dependent variable. The control must be a level of the independent variable and all changes are compared to it. Suppose the investigation question is, “How does the mass of a falling object affect the depth of its impact crater in sand?” The independent variable is mass and the dependent variable is the depth of the crater. The control for this investigation might be the smallest mass and all changes in mass could be compared to it.

Control as described above must be differentiated from a “control group” used in some experiments. A control group in an experiment is a group that is very similar to the experimental group but is not exposed to the independent variable. For example, when testing the effects of a new drug (independent variable), investigators will have a control group that does not receive the drug. Instead they will receive a fake or placebo which looks like the drug but does not contain the active ingredients of the drug.

For an investigation about the growth of plants that uses a control group visit

Materials List
A complete list of materials needed for the investigation should be given. Listing the necessary equipment and materials, along with writing procedures requires students to think thoroughly through the process to be used to test their investigation question.

Experimental procedures are detailed step-by-step directions for how to conduct an investigation. Following are the important elements of a good procedure:

  1. A description of the independent and dependent variables.
  2. Identification of variables to be held constant during the investigation, and identification of the control.
  3. An explanation of how to measure changes in the independent variable and the resulting changes in the dependent variable.
  4. A description of the safety rules to be followed during the investigation.
  5. The procedures should be numbered and explain exactly how to conduct the experiment. Well written procedures can be followed by others.
  6. Repeated trials should be included as part of the procedures.

Data Collection and Analysis 

Data Tables  The collection of data requires the use of science process skills to carry out the testing designed to obtain the information needed to solve the investigation problem. Collected data is compiled on data tables. Data tables provide a way of organizing information. The independent variable is located on the first column of the data table and the dependent variable is located to the right. Figure 1 below shows an example of a data table;

Independent variable

Dependent variable
Time in seconds

Speed in meters per second

Trial 1

Trial 2

Trial 3

















Graphs provide a picture or visual pattern of the data represented on a data table. Three types of graphs are commonly used to display data in middle school science investigations; bar graphs, line graphs, and pie graphs.

  1. Bar graphs are used to compare discreet variables.
  2. Line graphs are used to show changes over time or to compare two variables repeatedly.
  3. Pie graphs or charts are used to show percentages.

Setting up a bar or line graph

  1. The independent variable should be placed on the horizontal or x-axis. The dependent variable should be placed on the vertical or y-axis. For example, if the independent (cause) variable is “time in seconds,” and dependent (effect) variable is “speed in meters per second,” the axes of the graph are labeled as shown below.

  1. Choose the scale for the x and y axes. Evenly spaced intervals that include all of the data should be used. The choice of scale is very important as it can create bias in results.
  2. Give the graph a title. The title should describe what the graph is about and should include the independent and dependent variables. For example, a title for the above graph might be, “Speed versus time.”
  3. Plot the data on the graph.

When constructing a bar graph the bars should not be touching each other as is shown in the bar graph in Figure 2.

Quantity Demanded v. Price of Corn

Figure 2. A simple bar graph

The line on a line graph shows the shape or pattern of the data. If the independent and dependent variables are directly proportional a straight line will result as shown in figure 1A. If the independent and dependent variables are inversely proportional the shape of the line will look like that in figure 1B.

(A) (B)
Figure 3: (A) directly proportional relationship.  (B) Inversely proportional relationship

Often the pattern of the data is shown with a “line of best fit.” A best fit graph line is a continuous smooth line that flows through most of the data points but does not need to touch all of them. A best fit graph is an excellent way to show averages and can be useful for predicting data trends.  Data can be predicted between existing data points (interpolation) or beyond existing data points (extrapolation). Figure 4 shows an example of a line of best fit on a scatter plot graph.

Figure 4. Scatter plot with Best Fit Line.

Pie graphs
Pie graphs are shaped like a circle and are used to show percentages. The size of each section or “slice” is based on the percentage that it represents. A full pie is equal to 100%. Pie graphs show the independent and dependent variables just as bar and line graphs do. The independent variable is what the pie slice represents and the dependent variable is the size of each pie section.

The Percentage of Water Group Needs by 2050
pie chart of types of water user groups with needs by 2050

Figure 5. An example pie graph or chart.

Analysis of Results
During the analysis of the results the data and supporting evidence are presented.
Results should be analyzed both quantitatively and qualitatively. Quantitative results are obtained through the measurements and calculations gathered during an investigation. Qualitative results include non-numerical observations made during the investigative process.

For a more detailed discussion of quantitative and qualitative results see
MS TIPS benchmark N.8.A.4

Given multiple experiments addressing the same problem, students should be able to compare, contrast and analyze the meaning of the compiled results. Following is an example of this process occurring in an inquiry-based investigation:

During whole-class brainstorming Mr. Jackson’s science class decided to design investigations to answer the question, “How does adding mass to a cart affect its speed as it falls down a ramp?” The class divided into six teams and each team designed their own investigation. After collecting their data and recording it on the computer, Mr. Jackson projected the data onto a screen for the class to analyze. Four of the teams’ data showed that increasing mass did not affect the speed of the falling cart. Two teams’ data showed that it did.

Conflicting results such as those described in the above scenario are common in middle school inquiry investigations. Thorough analysis of the results is important in order to prevent the possible reinforcement of misconceptions. Small group followed by whole-class discussion that includes critical analysis of the data patterns and aberrations to the patterns are important parts of the inquiry process. When students struggle with the process of interpretation they begin to understand the importance of careful, controlled investigation and attention to detail.

Many extended learning opportunities can result from such a process. Students might follow-up on the problem through further investigation, research on the web, and reading about the topic in textbooks.

An important reason for students to compare experimental results is to help them to gain an understanding of why scientists repeat each others experiments, and make their procedures and data available for scrutiny and criticism. Sharing results also forces students to face the validity of their own conclusions. Just as scientists do, students may find it necessary to modify or even abandon their previously accepted ideas.

Drawing conclusions based in scientific investigations, and justifying claims made in those conclusions is very challenging to middle school students. With repeated practice however students will be able to develop and write complete conclusions. Following is a list of the statements and questions representing the components of a complete conclusion:

  1. Restate the problem or investigative question. Link the results to the original question.
  2. Restate the hypothesis.  Do the results of the investigation warrant accepting the hypothesis as a plausible explanation for the research question? Will further testing be needed, or will another hypothesis need to be made?
  3. Write about weaknesses in the experimental design and how they might be improved in future investigations.
  4. Explain how the experimental results relate to events in the real world.
  5. Make recommendations for further related problems for investigation.

For a more information about experimental design see MS TIPS benchmark N.8.A.4.

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Performance Benchmark N.8.A.6

Students know scientific inquiry includes evaluating results of scientific investigations, experiments, observations, theoretical and mathematical models, and explanations proposed by other scientists.  E/S

Common misconceptions associated with this benchmark

1. Students commonly incorrectly perceive science as simply doing experiments and acquiring previously gathered content knowledge.

More often than not they do not understand the importance of the process of inquiry to solving problems in science.

An excellent website for studying the nature and importance of scientific inquiry is sponsored by the NWREL Center for Classroom Teaching and Learning.

2. Students often hold the naïve perception that science is done in labs and not in the real world.

Although scientific inquiry does occur in research laboratory settings, it also occurs in natural settings. For example, field ecologists spend much of their time outdoors studying the organisms and processes of nature and the impact humans have on them. Geologists also spend a considerable amount of time making observations and conducting investigations in the outdoors. Inquiry also takes place within other environments such as hospitals, schools, and in the workplace.

For a list of hundreds of science-related jobs visit the website, New Scientist Jobs at

3. Students often think that there is always an explanation for everything.

Perhaps due to the cookbook nature of most middle school labs students often incorrectly believe that there is a correct explanation for everything and that all experiments should result in a correct answer to the experimental question.  Science is not a static body of facts and activities. Investigations often result in more questions and problems.

For a complete description of what science is and isn’t visit

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Performance Benchmark N.8.A.6

Students know scientific inquiry includes evaluating results of scientific investigations, experiments, observations, theoretical and mathematical models, and explanations proposed by other scientists.  E/S

 Sample Test Questions

1st Item Specification: Know and practice scientific inquiry.

Depth of Knowledge Level 1

  1. Using the diagram, which statement is best described as an observation?


    1. The air in the cloud is rising to the top.
    2. The air in the cloud contains water.
    3. The cloud is getting darker near the bottom.
    4. Rain is starting to fall from the cloud.
  1. Four children can feel and smell an object inside a bag, but they cannot see it.  Which of the following is NOT an observation about the object?
    1. “It is flat at one end and round at the other.”
    2. “It smells like peppermint.”
    3. “It has a bump on it.”
    4. “I hope it is candy.”
  1. Whenever scientists carefully measure any quantity many times, they expect that
    1. all the measurements will be exactly the same.
    2. only two of the measurements will be exactly the same.
    3. all but one of the measurements will be exactly the same.
    4. the measurements will be close but not exactly the same.
  1. A student has the idea that studying longer will increase test scores.  Which is the best statement of this hypothesis?
    1. Test scores affect the time a student will study.
    2. If test scores increase, then the student studied longer.
    3. Studying longer will not affect test scores.
    4. If a student studies longer, then their test score should increase.
  1. Look at this picture of a candle.


    Which statement is a direct visual observation?
    1. The candle is lit.
    2. The candle is made of wax.
    3. The flame is hot.
    4. The candle is heavy.

Depth of Knowledge Level 2

  1. A cupful of water and a similar cupful of gasoline were placed on a table near a window on a hot sunny day. A few hours later it was observed that both the cups had less liquid in them but that there was less gasoline left than water. What does this experiment show?
    1. All liquids evaporate.
    2. Gasoline gets hotter than water.
    3. Some liquids evaporate faster than others.
    4. Liquids will only evaporate in sunshine.
  1. Cathy has two kinds of plant food, "Quickgrow" and "Supergrow." What would be the best way for Cathy to find out which plant food helps a particular type of houseplant grow the most?
    1. Put some Quickgrow on a plant in the living room and put the same amount of Supergrow on the same kind of plant in the bedroom. Take care of them the same way.  See which one grows the most.
    2. Find out how much each kind of plant food costs.  The more expensive kind is probably better for growing plants because it contains more nutrients.
    3. Put some Quickgrow on a plant. Put the same amount of Supergrow on the same kind of plant. Put both the plants in the same place and care for them in the same way. See which one grows the most.
    4. Look at the advertisements for Quickgrow. Look at the advertisements for Supergrow.   See which one says it helps plants grow the most.
  1. A student wants to perform an experiment to test how much water a bean plant needs for good growth. Which factor should be changed?
    1. The amount of light
    2. The amount of water
    3. The type of soil
    4. The type of bean plant
  1. Bill wants to find out whether seeds grow better in the light or the dark.  Bill could put some seeds onto pieces of damp paper and keep
    1. all the seeds in a warm, dark place.
    2. one group in a light place and another in a dark place.
    3. all the seeds in a warm, light place.
    4. each group in a light or dark place that is cool.
  1. Jerry had an idea that plants needed minerals from the soil for healthy growth.

He placed a plant in the Sun, as shown in the diagram below.

   In order to check his idea, he also needed to use another plant.


Which of the following plant choices should he use?

  1. Image 1
  2. Image 2
  3. Image 3
  4. Image 4

2nd Item Specification: Use reliable data collection, accurate graphing, experimental design and experimental controls.

Depth of Knowledge Level 1

  1. The graph shows the progress made by an ant moving along a straight line.


How far did the ant travel in 15 seconds?

  1. 1.5 cm
  2. 2.0 cm
  3. 2.5 cm
  4. 3.0 cm
  1. The graph shows the progress made by an ant moving along a straight line.


How long did it take to travel 2.5 cm?

  1. 10 seconds
  2. 13 seconds
  3. 15 second
  4. 17 seconds

Depth of Knowledge Level 2

  1. The graph shows the progress made by an ant moving along a straight line.


If the ant keeps moving at the same speed, how far will it have traveled at the end of 30 seconds?
  1. 5 cm
  2. 6 cm
  3. 20 cm
  4. 40 cm
  1. Sandy collected the gas given off by a glowing piece of charcoal. The gas was then bubbled through a small amount of colorless limewater.   Part of Sandy’s report stated, “After the gas was put into the jar, the limewater gradually changed to a milky white color.” This statement is a(n)
    1. observation.
    2. conclusion.
    3. generalization.
    4. hypothesis.
  1. An experiment was conducted to determine the feeding rate at which two different water beetles eat frog eggs. The data are shown in the following graph:


How many frog eggs did Beetle B eat in the first 4 minutes?
  1. 20
  2. 30
  3. 60
  4. 90
  1. The following data table was made for an experiment:

mass of graduated cylinder

156.87 g

volume of graduated cylinder

100.0 ml

mass of graduated cylinder and alcohol

200.57 g

volume of alcohol in graduated cylinder

55.3 ml

Based on the analysis of the data, the mass of the alcohol used in the experiment is
  1. 56.87 g
  2. 55.3 g
  3. 44.70 g
  4. 43.70 g
  1. Use the data table to answer the question below.


Which statement is valid based on the data in the table?

  1. Oxygen production is greater near the surface because there is more light.
  2. Oxygen production is greater near the bottom because there are more plants.
  3. The greater the water pressure, the more oxygen production occurs.
  4. The rate of oxygen production is not related to depth.

3rd Item Specification: Given multiple experiments addressing the same problem, compare, contrast, and analyze the meaning of all the results.

Depth of Knowledge Level 1

  1. Two companies make golf balls, and each claim that its ball goes farther. Which would be the best scientific evidence to decide which ball goes farther?
    1. You ask the best 100 golfers in the world which ball goes farther.
    2. You read results of tests conducted on the two balls by both companies.
    3. A machine hits each ball with exactly the same force, and you measure how far each of the balls go.
    4. The best golfer in the world hits each ball 100 times, and you measure how far each of the balls go.
  1. Julie had four bottles. She wanted to know which bottle could hold the most water.  Julie found the mass of each bottle when it was empty. Then she found the mass of each bottle when it was full of water. She recorded the following results.


Mass of Empty Bottle (g)

Mass of Full Bottle(g)













Which bottle held the MOST water?

      1. Bottle 1
      2. Bottle 2
      3. Bottle 3
      4. Bottle 4

Depth of Knowledge Level 2

  1. These graphs show the rate at which four different disease-producing bacteria grow.


Which bacterium would produce a disease in the shortest
amount of time?

    1. Bacterium 1
    2. Bacterium 2
    3. Bacterium 3
    4. Bacterium 4
  1. The diagrams show different trials Greg carried out with carts having different-sized wheels. He started them from different heights and the blocks he put in them were of equal mass.

Greg wants to test this idea: 
The heavier a cart is, the greater its speed at the bottom of a ramp.


Which three trials should he compare?

    1. G, T, and X
    2. O, T, and Z
    3. R, U, and Z
    4. S, T, and U

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Performance Benchmark N.8.A.6

Answers to Sample Test Questions

  1. C, DOK Level 1
  2. D, DOK Level 1
  3. D, DOK Level 1
  4. D, DOK Level 1
  5. A, DOK Level 1
  6. C, DOK Level 2
  7. C, DOK Level 2
  8. B, DOK Level 2
  9. B, DOK Level 2
  10. C, DOK Level 2
  11. D, DOK Level 1
  12. B, DOK Level 1
  13. B, DOK Level 2
  14. A, DOK Level 2
  15. B, DOK Level 2
  16. D, DOK Level 2
  17. A, DOK Level 2
  18. C, DOK Level 1
  19. A, DOK Level 1
  20. A, DOK Level 2
  21. D, DOK Level 2

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Performance Benchmark N.8.A.6

Students know scientific inquiry includes evaluating results of scientific investigations, experiments, observations, theoretical and mathematical models, and explanations proposed by other scientists.  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. The Process of Scientific Inquiry

The Entomology Department University of Nebraska at Lincoln has a website called “Bumble Boosters” that offers lesson plans for teachers including a motivating inquiry investigation using squirt guns to hit a target. The purpose of the investigation is to provide students with an opportunity to develop and test a hypothesis and to recognize sources of variation in an experiment.

To access this investigation visit

2. Aspects of Experimental Design

The University of Tasmania, School of Agricultural Science has a website rich with information and activities including: (1) Discover How Scientists Discover, (2) Pit Your Detective Skills Against Some of Tasmania’s Brightest Scientists, (3) Making Sense of the Scientific Method with Real Live Examples, and (4) A Guided, Do-It-Yourself Resource for Understanding the Scientific Method.

Access their website at

3. Science Magazine

The American Association for the Advancement of Science (AAAS) offers a comprehensive selection of articles related to scientific inquiry in their magazine, Science Magazine. Membership is required for full access.

The AAAS website is

4. Inquiry Misconceptions

The HOB Mission website Robert Sweetland provides a comprehensive list of student misconceptions related to the process of scientific inquiry as well as misconceptions related to science content areas. The website also includes useful classroom inquiry rubrics for student interactions, teacher interactions during classroom inquiry, and for the classroom environment.

Access this information at

5. Colored Liquids Investigation Sequence

Robert Sweetland uses colored liquids in an investigative sequence that addresses the following questions: (1) How do scientists record observations? (2)How do scientists organize their records to see patterns? (3)How do scientists use observations to understand?
(4) How do scientists convince other scientists that their observations are accurate?

For this motivating investigation visit

6. Experimental Analysis

Environmental Science Activities for the 21st Century (ESA21) uses a computer simulation called Fish Farm to introduce the basics of designing experiments and analyzing data. Ready to print data tables, graphs, and follow-up questions are provided.

The computer simulation can be obtained through the project directors free of charge. Their web address is

7. Graphing Skills

Colorful and concise review of the basics of graphing can be accessed at the following websites:

8. Understanding Evolution for Teachers

The California Museum of Paleontology has articles and lab and web activities related to helping students to understand the nature of science. The lessons include a variety of activities including data analysis and interpretation, web-based activities, games, and participation in an imaginary fossil hunt.

To access these lessons visit

9. The Nature of Science

Science for all Americans Online provides a thorough analysis of the nature of science and the process of scientific inquiry.

To access is interesting article visit

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Benchmark Related Vocabulary

Scientific evidence
Scientific knowledge
Scientific progress