Lesson 9

Planning a Controlled Experiment: Jason's Revenge - or is it?

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SWBAT collaboratively plan a controlled experiment that is a fair test, and includes repeated trials.

Big Idea

How do scientists plan their experiments? What do they include in their plans? Students develop a written plan in their notebooks that will be used to conduct a controlled experiment.

Setting Up the Investigation

Connection to The Next Generation Science Standards

In this investigation, students begin the work that will lead to their ability to demonstrate the following Science Practices; conduct an investigation collaboratively to produce data to serve as the basis for evidence, using fair tests in which variables are controlled and the number of trials considered (5-PS1-4); measure quantities such as weight to address scientific problems (5-PS1-3); and demonstrate the Crosscutting Concept of using a cause and effect relationship to explain change (5-PS1-4).

*  Although students are beginning to address the Disciplinary Core Idea that matter of any type can be subdivided into particles that are too small to see, but even then the matter still exists and can be detected by other means (5-PS1.A) - that is not the emphasis for this lesson and will be fully explored in later lessons in the unit.  This lesson will however, become another "touchstone" lesson for this concept.

Prep time for this lesson is approximately 5 minutes.

You will need the chart from yesterday (How To Plan A Controlled Experiment) along with the student copies of Plaid Pete's Guide to Planning A Controlled Experiment that were handed out at the end of the lesson.  Here is the link to yesterday's lesson Plaid Pete Guides the Way. 

Today, students will use what they learned about the parts of a controlled experiment yesterday, to actually write one.  They will be writing a complete experiment, including a two part testable question, materials list, and a procedure.


One copy of What's The Matter Plaid Pete?- Lab Scenario Sheet Lesson 7 for each student

One copy of What's The Matter Plaid Pete?- Practice Writing 2 Part Questions for each student (optional)

Focus & Motivation

5 minutes

Students Read Scenario in Teams

I hand out the Copy of What's The Matter Plaid Pete?- Lab Scenario Sheet Lesson 7 that I read to students in the previous lesson.  This time, I ask them to read it in their Research Teams.  When teams are finished, I ask clarifying questions to ensure students understand the scenario.

I tell them, "Now that you understand that Controlled Experiments are a special type of Scientific Investigation, we are ready to begin the process of planning a "fair experiment" to settle this disagreement."

Share Lesson Objective & Success Criteria

Note:  Consistent with the Sheltered Instruction Observation Protocol, I am now including a language objective with each lesson.  These objectives were derived from the Washington State ELP Standards Frameworks that are correlated with the CCSS and the NGSS.

I share the lesson objectives and success criteria:

Learning Objective:  I can plan a controlled experiment with my class, in which I have used "fair tests" and repeated trials.

Language Objective:  I can communicate a sequence of events in writing using temporal and other transitional/linking words (e.g. first, next, therefore, etc.).  [ELP.4-5.9]

Success Criteria:  I have completed all steps of the process correctly in my Science Notebook.

Guided Instruction

45 minutes

Since this is the first controlled experiment that students will plan, I want to follow a replicable format.  

This is the How to Plan a Controlled Experiment Chart that our class created yesterday, and that we will use as a reference today.

Notebook Write-Up

I remind students about the examples of Alexander Graham Bell's Notebook that we looked at during our lesson on models.  I tell them, "All good scientists keep these kinds of explicit records of every experiment they conduct - right down to the last little detail.  So today, I am going to show you how we will set up every controlled experiment that we will conduct this year.  It is very important that you follow this process.  In Science, it is an accepted practice that you give enough detail so that another scientist could come along behind you, conduct the same experiment, and get the same results."

I ask students to open their Science Notebooks, and turn to the next clean page (giving the page number because we are all on the same page!).  Then, I ask students to get out their Plaid Pete's Guide to Planning A Controlled Experiment that was handed out in the last lesson, and remind them that yesterday I told them that this guide had specific information that would help us today. 

I ask my students for an appropriate name for this experiment.  They come up with one and we write it as a heading, and write the date.  I model it for them in my Science Notebook that is on my document camera:

Soda & Candy Investigation          Date

I ask students, "What is the first step in a controlled experiment?" and Cold Call on a student to answer.  Cold calling is a strategy I will use throughout this lesson.  Today is a very necessary part of instruction, but it can get tedious for students and it is easy for them to "zone out" - so I want to keep them on their toes!  I am given the correct answer, "Ask a Testable Question."  I tell students, that will be the first section of the Notebook Write-Up of our experiment.  I skip a line and center my next heading:


I then ask my scientists to look at Plaid Pete's Guide and see what he says about asking a testable question, then turn and talk to their partner.  I call for a response, and confirm that yes, it needs 2 parts.  I then work with my students to identify the two parts of the question for the scenario portrayed in the What's The Matter Plaid Pete? Lab Scenario sheet  - Lesson 6.  The question we write under the heading looks something like this:

How does the type of liquid affect the time it takes candy to dissolve?

I tell my students that we had probably better add a bulleted note to our How to Plan a Controlled Experiment chart from yesterday.  Underneath 1.  Ask a Testable Question, I add this bullet (Note - I am keeping what I write the most necessary information and as simple as possible, as students will be copying this into their notebooks)

  • Has 2 parts that show a relationship between the independent variable and the dependent variable

The next section, Hypothesis, is difficult for most students, and they need time and support to grapple with wording variations until they find something that everyone can agree on that makes sense.  We end up with something that looks like this:


If candy is placed in soda pop instead of water, then the time it takes to dissolve will ________, (increase, decrease, stay the same)  because _________.

Before students answer the "because" part, I give them a piece of paper and have them list their observations and background knowledge about how soda pop and water affects things that are placed in them.  This step is important.  Even if students just copy another student's answer, they are learning that they have to provide some kind of reason that is based on thinking.

We then add a bulleted list to the How to Plan a Controlled Experiment chart under 2. Hypothesis:

  • Form as an if, then statement to show cause and effect between the variables

We move on to the next part of a controlled investigation.  I ask my students to look at the bullets that we included on our chart yesterday under 3. Plan, and note that we have to include materials and an Investigation Set-Up Diagram.  I tell my students,

"When you plan a controlled experiment you also have to write a set of step by step directions that tell the scientists who come after you exactly how to repeat what you have done.  This is called a procedure.  It would be hard for us to list our materials or draw our diagram, until we write our procedure.  However, a good scientist puts the materials list and diagram before the procedure so the scientist can gather the materials and get a picture of what they need to do.  We are going to add our headings, leave space, and then come back and fill those in.


Investigation Set-Up Diagram

I have students look at Plaid Pete's Guide and notice anything we missed from yesterday that we should probably include.  My new bullets look like this:

  • Include repeated trials
  • Include instructions to "record data"

I write the next heading:


We work together to come up with a step by step numbered procedure for an experiment that tests the effects of the two types of liquid on the time for the candy to dissolve.  I have tried a number of pop and candy combinations, and the best for this experiment is Mentos and Diet 7-Up.  I show the students the 8 oz. Solo plastic cups we will use in the investigation and a graduated cylinder.  We decide together that 50 mL of soda would be enough.  (Don't worry - you won't get the kind of explosive geyser with this combination that you may have previously seen).  When we are finished, our directions look something like this:

1.  Set up the cups as shown in the investigation set-up diagram.

2.  Measure exactly 50 mL of water and place in cup A.

3.  Measure exactly 50 mL of lemon-lime soda and place in cup B.

4.  Place candy in each of the cups at exactly the same time.

5.  Record observations in the data table for 0 minutes.

6.  Record observations at 5 minute intervals until at least 1 of the pieces of candy dissolves.

7.  Repeat steps 2-6 two more times as trials 2 and 3.

(It will take approximately 1 hour for the candy to dissolve - so I tell my students that tomorrow when they do the experiment, they will collect data from 2 other teams as their trial 2 and trial 3 data - because we must have repeated trials!)

We go back and check our procedure against the chart, asking these questions:  Do we have only 1 independent (manipulated/changed) variable?  Do we have only 1 dependent variable (responding/measured)?  Do we have a measuring tool?  Do we have a direction to record data?  Do our steps make sense, such that somebody else could replicate them?

Once we are satisfied with the procedure, we go back and make a materials list, and construct the investigation set-up diagram.

This is an example of a Student's Science Notebook.

Finally, I ask for student responses about what our next section should be.  I call on a student who responds appropriately, and I write in my Science Notebook.


When we begin discussing our data table, I have to remind students about the dependent (responding/measured variable) by asking the question, "What are we measuring?  We go back and look at our question, and are able to determine that this variable is time.  Because this is a "touchstone" lesson for later concepts, I also want students to be paying attention to what happens - so I ask them if there are any qualitative observations that we might also need to note.  I prompt and prod until I get another student to suggest that perhaps we should draw a model so that we have a good record later of what happened during this experiment.  It takes a bit of questioning, but we create a data table that looks like this:

Student data table.  As you can see, this was the completed table after the experiment was conducted.  This was one of my English Language Learners, and I do believe having the model in the table helped this student to better analyze the data in the experiment.  In this way, the model became a vehicle for understanding.

I tell my students that that is all we will do in our Science Notebooks for today - the remainder of our job in recording what we have done as scientists will come during and after our investigation.

Reflection & Closure

5 minutes

Setting the Stage

I tell students, "Wow - great work!  We are going to be ready to begin our experiment at the beginning of our Science period tomorrow!"

I am amazed!  This is one of the lessons of the year that I dread the most.  I am always worried that it will be tedious and boring.  

My students have loved it!  The focus on constructing their notebooks in a way that another scientist could come back and recreate their work has really paid off!  In this Example 1 is a student who experienced difficulty completing their notebook neatly and carefully.  As you can see in Example 2 this very same student is now taking ownership of their work.  The notion that a scientist's work can be called forth for examination long after they are gone has really left an impression.  

Note:  Some students may need additional practice constructing 2 part questions.What's The Matter Plaid Pete?- Practice Writing 2 Part Questions will provide additional practice.