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Critical Thinking in Science

Part 1: Introduction to Experimental Design


Students will learn and implement experimental design vocabulary while practicing their critical thinking skills in an inquiry based experiment. This lesson is written using the 5E Learning Model.

Learning Outcomes:

  • Students will define and apply the experimental design vocabulary.
  • Students will use the experimental design graphic organizer to plan an investigation.
  • Students will design and complete their own scientific experiment.

Curriculum Alignment:

1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.

1.02 Develop appropriate experimental procedures for:

  • Given questions.
  • Student generated questions.

1.04 Analyze variables in scientific investigations:

  • Identify dependent and independent.
  • Use of a control.
  • Manipulate.
  • Describe relationships between.
  • Define operationally.

1.05 Analyze evidence to:

  • Explain observations.
  • Make inferences and predictions.
  • Develop the relationship between evidence and explanation.

1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations:

  • Measurement.
  • Analysis of data.
  • Graphing.
  • Prediction models.

1.08 Use oral and written language to:

  • Communicate findings.
  • Defend conclusions of scientific investigations.
  • Describe strengths and weaknesses of claims, arguments, and/or data

Classroom Time Required:

Approximately 6 class periods (~50 minutes each) are needed, however, some things can be assigned as homework to decrease the time spent in class.

Materials Needed:

  • Overhead transparency of Experimental Design Graphic Organizer
  • Student copies of: Experimental Design Graphic Organizer, Vocabulary Graphic Organizer, Explore worksheet, Explain worksheet
  • Supplies for experiment: Dixie drinking cups, Pepsi and Coke (~1.5 to 2 ounces per student) Possibly ice to keep soda cold
  • Copies of worksheet, Overhead, Small drinking cups (2 per student), Pepsi and Coke
  • Dictionaries or definition sheets for the vocabulary words

Technology Resources:

  • Overhead Projector

Pre-Activities/ Activities:


  • What are the “rules” for designing an experiment?
  • Teacher and class will discuss the following questions:
  • Is there a specific way to design an experiment? (Try to get them to mention the scientific method and discuss any “holes” in this.
  • Are their rules scientists follow when designing an experiment?
  • Are all experiments designed the same?
  • What kinds of experiments have you done on your own? (Good things to discuss are cooking, testing sports techniques, trying to fix things, etc….. Try to relate experimentation to their everyday life.)


  • Review an experiment and answer questions.
  • Students will read a description of an experiment and answer questions about the design of the experiment without using the vocabulary. (See Worksheet 1)


  • Vocabulary introduction and application
  • Students will define the experimental design vocabulary using the graphic organizer (See Worksheet 2).
  • Independent variable, Dependent variable, Control, Constant, Hypothesis, Qualitative observation, Quantitative observation, Inference (Definitions available)
  • Students will review the worksheet from the explore section and match the vocabulary to the pieces of the experiment. Review answers with the class.
  • Students will read a second experiment description and identify the pieces of the experiment using their vocabulary definitions (See Worksheet 3).


  • Introduce Experimental Design Graphic Organizer (EDGO) and complete class designed experiment.
  • The teacher should review the EXAMPLE PEPSI VS COKE EDGO for any ideas or questions
  • Use overhead projector to review the blank EDGO and complete as a class (See Worksheet 4)
  • Tell the class that you are going to do the Pepsi Coke Challenge. The question they need to answer is: Can girls taste the difference between Pepsi and Coke better than the boys?
  • As a class, plan the Pepsi verses Coke experiment. This is a good time to discuss double blind studies and why it is important to make this a double blind study. Students can look at the results within their own class as well as the whole team.
  • This is a good chance to also test multiple variables. You do not need to let students know this, but if the data chart also records things like age, frequency of drinking soda (daily, weekly, monthly, rarely), ability to roll tongue, or anything else they think might be interested in, the results can be analyzed for each variable.
  • Complete experiment and analyze data (See Worksheet 5 and 6). Students should make a bar graph of their results (each variable verses percent correct). As a class you should discuss the reliability of the results: Does gender actually affect your ability to taste?
    • HINTS:
    • I removed labels from the bottles and labeled them A and B. I used a different labeling system for under the cups so the students did not see a pattern (numbered cups were Pepsi, lettered cups were Coke).
    • I recorded the data and organized the tasting while students completed other work in their seats. Two students at a time tasted the soda and I recorded data. You could also have a volunteer who is not participating help with this.
    • Check for students who do not want to drink soda as well as any dietary needs such as diet soda.
    • Do not verify guesses until all of the classes have completed the experiment.


  • How can you accurately remember the pieces of an experiment?
  • Students should choose one of the following or some other teacher approved choice(See Worksheet 7):
    • Write a poem about four of the vocabulary words.
    • Write a song about four of the vocabulary words.
    • Create a memorization tool for four of the vocabulary words.
    • Make a poster about four of the vocabulary words.

Teachers should evaluate these choices to ensure they show an understanding of the vocabulary.


See Evaluate piece of Activities Section.


  • A different experiment can be designed in the Elaborate section.
  • EDGO can be edited for any motor skill deficiencies by making it larger, or making it available to be typed on.
  • All basic modifications can be used for these activities.

Alternative Assessments:

  • Make necessary adjustments for different experiments.

Critical Vocabulary

  • Independent Variable- the part of the experiment that is controlled or changed by the experimenter
  • Dependent Variable- the part of the experiment that is observed or measured to gather data; changes because of the independent variable
  • Control- standard of comparison in the experiment; level of the independent variable that is left in the natural state, unchanged
  • Constant- part of the experiment that is kept the same to avoid affecting the independent variable
  • Hypothesis- educated guess or prediction about the experimental results
  • Qualitative observation- word observations such as color or texture
  • Quantitative observation- number observations or measurements
  • Inference- attempt to explain the observations


This is the first lesson in the Critical Thinking in Science Unit. The other lessons continue using the vocabulary and Experimental Design Graphic Organizer while teaching the 8th grade content. Students are designing their own experiments to improve their ability to approach problems and questions scientifically. By developing their ability to reason through problems they are becoming critical thinkers.