Lesson 17

Changing Matter: Plaid Pete Knows Conservation!

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SWBAT describe and provide evidence for The Law of Conservation of Matter.

Big Idea

What happens when matter changes state? Do particles disappear? Students measure and graph materials, before and after changes of state, to provide evidence for conservation of matter.

Setting Up the Investigation

Connection to The Next Generation Science Standards

In this investigation, students explore the  Disciplinary Core Idea of Structure and Properties of Matter -  the amount (weight) of matter is conserved when it changes form, even when it seems to vanish. (5-PS1-2); and use the Crosscutting Concept of Scale, Proportion, and Quantity  - standard units are used to measure and describe physical quantities such as weight, time, temperature, and volume (5-PS1-2), and Energy and Matter - energy can be transferred in various ways and between objects (5-PS3-1).

Please Note:  The Lexile Level for What's The Matter Plaid Pete? - Lab Scenario Sheet Lesson 16 is 780 (5th Grade Range is 740 - 1010).

The Preparation Time for This Investigation is approximately 10 minutes.

Materials Needed:

One copy for each student of What's The Matter Plaid Pete?- Lab Scenario Lesson 17

One copy for each student of What's The Matter Plaid Pete?- Lab Sheet Lesson 17

One quart sized plastic bag for each team of students

One chocolate candy bar for each team of students

One liter plastic container for each team of students

One large carafe of of very warm water to share between the teams

One small plastic water bottle for each team of students

One graduated cylinder for each team of students

One straw for each team of students

One balloon for each team of students

Safety glasses for each student

One balance for each team

Mass cubes for each team

Ruler for each team

White vinegar 

Baking Soda

Paper Towels

One materials tub for each team of students


Focus & Motivation

5 minutes

Introduce the Scenario

I gather my scientists together and tell them that today we will meet another member of Plaid Pete's family, his younger sister.  I say, "I wonder what she is like?"  I hand out copies of What's The Matter Plaid Pete?- Lab Scenario Lesson 17 to each student. 

Students agree on and highlight their own parts.  They are reading the scenario as a Reader's Theater script.  These scenarios are an engaging way to "hook" students into the Science investigation, as well as a wonderful opportunity to integrate literacy.  They get right to work reading the scenario.  I am pleased to see that long with an improvement in Science content knowledge and skills, the scenarios are producing an increase in reading fluency skills as well.

I tell my students, "It looks like we will again be looking at what happens when matter changes.  Please answer the two questions at the bottom of the scenario sheet.  I give them a few moments to work independently to do this.  These questions are a pre-assessment, and will give me some ideas about their pre-conceptions and misconceptions about conservation of matter.  I collect the sheets when students are finished, as I want to look through them and compare them to their lab sheets after the investigation.  I will be looking to see if they have changed their ideas.

Share Lesson Objective & Success Criteria

Note:  Consistent with the Sheltered Instruction Observation Protocol, I am now includinga 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 describe The Law of the Conservation of Matter, and provide evidence to support it.

Language Objective:  I can construct a claim and support it with evidence.  [ELP.4-5.4]

Success Criteria:   I can correctly complete a claims and evidence sheet in my notebook supporting The Law of the Conservation of Matter.

Guided Exploration

35 minutes

Introducing Open and Closed Systems

I explain to my students that today, as Plaid Pete stated in the scenario, we will be working with closed systems.  I show them a plastic quart sized bag that has been zipped closed.  I state, "This is a closed system," demonstrating that it is sealed.  I open the bag and state "This is an open system."  I ask my students, "Why do you think Plaid Pete specified a "closed system" when he explained to Priscilla about the pieces of candy bar?"

I ask for a volunteer, and accept the answer that it wouldn't be a fair comparison if pieces were allowed to fall out or escape.  

Explain the Lab Sheet

I hand out the What's The Matter Plaid Pete?- Lab Sheet Lesson 17 and call students' attention to the first activity.  I read through the sheet with students, and ensure that they understand the directions.  We look at Activity Two, and again read through, discussing the need to keep the bag sealed.  Finally, we read through the instructions for Activity Three.  As expected, many students have had experiences with baking soda and vinegar and are quite excited about this activity.  I explain the need to do each activity carefully, and that I have decided that we will all complete the first two activities, before we move on as a class to the third activity.  If I don't do this, I know they will rush through, completing the first two activities thoughtlessly.  

I also explain that as teams complete the table that lists the change in mass, I will be asking teams to record their data on the class graph that I have constructed on chart paper.  (I will need to insert a picture of the graph here)

Choosing Jobs

There are a number of jobs, and I allow my students time to decide how they will work to complete each of the activities.  They know they cannot begin until I have seen and approved their job list.  This is a Video Clip of students showing me their job list from a different investigation, however it is a similar format and procedure to all of our investigations.

Once I have done so, I instruct team leaders to go to the materials table to retrieve their materials tubs and begin the first two activities.  I have purposefully not included the materials for Activity Three.

Activity 1 & 2

I move among my teams, ensuring they are following directions, and watching their measurements and calculations.  Students work to calculate the mass of the whole candy bar.  Then they break up the candy bar into pieces and calculate the mass of the pieces in the closed system.  They determine the difference in the mass, and record it on the class graph.  Then, they melt the candy bar still inside the closed system.  As I move among the teams, I am asking students to verbalize what they see - using their Science vocabulary.  

Activity 3   

When all teams have completed the first two activities, I call my students to attention and ensure they understand the directions for the third activity, particularly the direction for not mixing the vinegar with the baking soda.  I model the procedure for attaching the balloon to the plastic bottle, as I know this will be difficult for some students.  I shouldn't have worried - they are taking this very seriously!  They carefully measure the line on their bottles so they know how much vinegar to pour into them.  And work just as carefully to measure the baking soda and place it into the balloon.  It is exciting to watch the ooohs and aahhs as the balloon fills up!  You can see their excitement in this Video Clip  I then have my students work in their teams to answer the final question at the bottom of the lab sheet.  


I point out that we have had the opportunity to observe matter change state in a closed system.  I ask my scientists what they noticed.  They are full of comments and observations.  Some have noticed that there is no change in mass, but others aren't quite there yet.  I say, "Wow, we have collected a lot of data.  I think it is time we made some sense out of all of this.  Let's get some more information."


10 minutes


I say to my students, "In our previous investigations, we discovered that changes in state are caused when heat is added or taken away from matter, because it changes the movement of the particles. Today, we have been asking the question about whether or not the number of particles in matter changes when matter changes state.  The answer to that question can be answered by something called "The Law of the Conservation of Matter."

I share the following video with my students.


I return to point to the class graph where we collected our data.  I ask, "According to the data we collected, was there a change in mass when the materials we were working with changed state?  We have to go back to an earlier discussion of "messy data."  And we identify that we have "outliers" or data that are far outside the rest of our data.  Students at this age and stage want everything to be exact, so getting them to realize that all measurement is relative is an important concept.  I have to bring out a gram cube to show them the difference that one gram makes, and demonstrate how easy it is to have that kind of difference on the balances that we use.  Students come to realize that they aren't very sophisticated instruments.  

I ask, "Do we have evidence that there was no change then in the number of particles when these materials changed state from one form to another?"  I call on a student and receive the answer that yes, overall - we do have evidence and our evidence is that even though a state change occurred, there was no difference in mass, so there must be the same number of particles afterwards as there was before.  

I tell my students to get out their Science Notebooks and write the date in the upper right hand corner.  Then I ask them to copy the following on the next clean page:

The Law of Conservation of Matter

  • Matter cannot be created or destroyed.
  • The mass of an object, or collection of objects, in a closed system never changes, regardless of the type of change that occurs.  Matter is conserved, or remains the same.

I tell my students that they will use the information they just received to complete a short activity in their teams to demonstrate their mastery of the learning objective.

Team Activity

10 minutes


I place the following prompt on the whiteboard:  

Plaid Pete had a metal box with a mass of 350 g., and some crayons that had a mass of 200 g.  He placed 100 g. of the crayons inside the metal box with the lid closed.  Then, the box was left out in the sun and the crayons melted.  On the next clean page in your Science Notebook, make a T- Table, Claims and Evidence Chart.  Under the claims section write:

I claim that the number of particles in the box after the crayons melted was/was not (choose one) the same.

Under the evidence side, list bulleted points of evidence using anything you learned in today's investigation that would help you to support your claim.

I tell my students to work in their team to complete this prompt in their Science Notebooks. I tell them I will only give them 10 minutes, so they need to discuss it and work quickly.  This is an example of one student notebook response.

Reflection & Closure

5 minutes

Share Out Answers

I call my students to attention.  Before I collect the notebooks, I ask a few students to share out how they answered the prompts.  There are a number of answers discussed in this Video Clip  I ask team leaders to collect the Science Notebooks and place them on the back table.  I tell my students I will take them home this evening, and they will get them back tomorrow with feedback on their prompt.  I explain that this is one of the kinds of prompts they will have on their final test, and that it is important they be able to use the information they have learned to construct claims and evidence statements.