Monthly Archives: September 2021

Developing a Particle Model of Matter

On September 15, we started Lesson 2-3 of The Garbage Unit. This lesson develops the idea that solids and liquids are made of particles and uses this idea to explain sugar dissolving in water. The day before this lesson, students made predictions about what happens to sugar when we dissolve it in water. Most students believed the sugar was still there because they could taste it in the water. Some students said that it was not still there because it disappeared. I asked them how they could gather evidence to determine if the sugar was still there. They suggested tasting the water. I reminded them of our prior investigations that used weight as a property and asked how we could use weight to see if the sugar was still there. Some students suggested that the weight could be evidence.

On the first day of this lesson, students investigated mixing sugar into water. They measured 50 ml of water and weighed the water. They weighed a spoonful of sugar. Then they mixed the sugar into the water until it dissolved. They weighed the mixture. While students were following directions and making their measurements, I circulated the room. I noticed that some students were getting erroneous data because they were not taring the scale correctly. I helped three of the six groups collect a second set of data to ensure they would all have accurate data to use to answer the four questions. If (I had not done this, they would not have noticed that the pattern that they need for later— that the weight of the water and the weight of the sugar add up to equal the weight of the mixture.)

Students answered four questions about the investigation with their groups. I collected the papers to see their thinking. One issue I noticed was that many students did not understand the concept of volume. When asked what happened to the volume after the sugar was mixed in, most students used the weight data to answer the question, rather than thinking about the amount of liquid in the cup.

I filmed a demonstration of the investigation to show as a review the next day to ensure all students could make the observations they needed.

The next day, I returned their investigation papers and we talked about volume. This is an important idea that they need to explain in their models.

Markings to indicated liquid level

We talked about the marks we made on the cup to show the amount of space the liquid takes up, or its volume. First we marked the level of water, then we made a new mark for the level of the mixture. We decided that the volume did not change much, it increased a small amount. How could this happen? We needed to figure that out.

The second day focused on developing a particle model of matter. Students read a short article called What is matter made of?

From NYU SAIL The Garbage Unit Lesson 2-3

Then we discussed what we learned from the article. Solids and liquids are kinds of matter that are made of particles. All matter is made of particles.

Flinn Scientific

Next, we watched a video that showed a physical model for particles and discussed the model. In this model, ping pong balls were put in a beaker.

Flinn Scientific

Then marbles were added to the same beaker. The marbles fit in the spaces around the ping pong balls.

Adding the marbles to the cup did not change the volume much. We explained how the ping pong balls were like the water particles and the marbles were like the sugar particles. The water particles have empty space around them like the ping pong balls do. The smaller sugar particles can fit in the empty spaces like the marbles fit around the ping pong balls.

Students worked with a partner to talk about their ideas. Then they each completed an exit ticket that asked how the particle model could explain why the volume did not change much when sugar was added to water. I collected the exit tickets and found that many students only represented the sugar as particles, but not the water.

On the third day, we will review the information we have about mixing sugar and water. We have three sources of information—investigation findings, the reading, and the physical model in the video. I made a video to recap.

We will create our own system models that use particles to provide a cause and effect explanation of what we observed in the investigation. Students work collaboratively to create models using Google Slides. I made a template with a fixed background of the cup and spoon. Students can drag the particles to show how they are arranged. They create before and after models and write their explanations on a third slide.

In this lesson, students are using four crosscutting concepts together as they generate their explanation for the phenomenon of sugar mixing with water.

  • 3-5-CCC1.3: Patterns can be used as evidence to support an explanation.
  • 3-5-CCC2.1: Cause and effect relationships are routinely used to explain change.
  • 3-5-CCC4.2: A system can be described in terms of its components and their interactions.
  • 3-5-CCC5.1: Matter is made of particles.

Students are also using several science and engineering practices

  • 3-5-SEP2.4: Develop and/or use models to describe and/or predict phenomena.
  • 3-5-SEP4.2: Analyze and interpret data to make sense of phenomena, using logical reasoning, mathematics, and/or computation.
  • 3-5-SEP5.2: Describe, measure, estimate, and/or graph quantities such as area, volume, weight, and time to address scientific and engineering questions and problems.
  • 3-5-SEP6.2: Use evidence (e.g., measurements, observations, patterns) to construct or support an explanation or design a solution to a problem.
  • 3-5-SEP8.4: Obtain and combine information from books and/or other reliable media to explain phenomena or solutions to a design problem.

The lesson focuses on one disciplinary core idea

  • PS1.A Structure and Properties of Matter
    • Matter of any type can be subdivided into particles that are too small to be seen, but even then the matter still exists and can be detected by other means.
    • The amount (weight of matter) is conserved when it changes form, even in transitions where it seems to vanish.


Photo by Laker on

On August 31 we investigated what happens to materials when they are crushed.

Making Predictions

I asked students to think about a soda can that gets crushed and a piece of paper that gets torn into 100 pieces. I asked them to answer these questions in their notebooks.

When a material changes shape,

  • Is it still the same material?
  • Does the amount of the material remain the same?
  • Why do you think so?

Students compared their answers in groups. We found that we had different ideas about what happens to the amount of materials when it is crushed.

Carrying Out the Investigation

We had already decided the class before on things we would test in our crushing experiment. All groups tested an aluminum can, a piece of paper, and a cookie. Then they chose two items from other available materials, such as aluminum foil, wood sticks, and cardboard.


Cookie before crushing
Cookie after crushing

Students observed the properties of materials before and after crushing and weighed the materials before and after crushing. They gathered their data.

Analyzing and Interpreting Data

On September 1 we began analyzing our data to make sense of what happened during crushing. Groups looked for patterns in the property and weight data and figured out what those patterns meant.

I introduced the concept of evidence. We talked about the difference between evidence and opinion. We discussed examples of evidence. Evidence is important because scientists use evidence to make claims. I told the students that, as scientists, they would be using evidence to make claims. Scientists decide which claims are best by arguing from evidence. We discussed how scientists support or refute claims.

Creating Claim, Evidence, and Reasoning Collaboratively

We practiced making a claim and supporting it with evidence and reasoning. We made a claim about what happened to the type of material before and after crushing. We decided that the type of material was the same before and after crushing. We identified evidence from our investigation that supported the claim. For example, the cookie was black, rough, and dull before and after crushing. The foil was silver and shiny before and after crushing. Our reasoning was that materials have certain patterns of properties. If the material is the same, the properties should be the same.

We did notice that some properties could be different before and after crushing. For example, texture can change. The aluminum can was very smooth before crushing. Some students crushed their cans by stepping on them on the sidewalk. The rough sidewalk imprint changed the texture of the can.

Next Steps

Our next step in this investigation will be to make an evidence-based claim about the weight of the material before and after crushing. I’ve noticed in my circulating the room that some students have data that will support that the weight is the same before and after crushing, while others have data that will refute that claim. When we continue this investigation, I plan to have groups assemble their own claims, evidence, and reasoning. Then they will compare their claims, evidence, and reasoning to other groups, decide if they support or refute the claim and provide evidence and reasoning for that position. This will be our first scientific argument.

Before we have our scientific argument, I will show this video to review what a scientific argument is.

I will scaffold students’ scientific arguments with an organizer.

I added the level of certainty information to see how students respond to the discrepancies in their data and to connect to the video content. From my observations, I noticed there were issues with taring the scale that led to inaccurate measurements.

After each group fills out their organizers, they will compare their arguments with another group by trading papers. Then they will use sentence starters to give feedback about the argument.

Evaluating the Argument

First, they need to evaluate the argument.

  • Is the evidence relevant to the claim?
  • Do you trust the evidence?
  • Are there gaps in the cause and effect reasoning?
  • Is there another possible explanation?

Responding to the Argument

If they disagree with the argument they can:

  • Ask a question about the reasoning
  • Offer different reasoning
  • Offer a different claim. 
  • Look for other reasons for the evidence. 
  • Compare claims with known scientific facts. 
  • Make sure that all data is included.

If they agree they can:

  • Give additional evidence or reasoning

Supporting Student Responses

To support their responses, I offer some sentence starters.

To refute a group’s claim, evidence or reasoning they can:

  • (ask a question) Why did you think that?
  • (offer another reason or claim) I think that.. 
  • (look for other reasons) I think that happened because…
  • (compare to facts) I read (or was told)… 
  • (include more data) This data (share the data) refutes your claim.

To support a group’s claim, evidence, or reasoning they will

  • (Add more evidence or reasoning) My data showed that…

I am looking forward to my students’ first scientific argument. Stay tuned…

Systems Models

Photo by Andrea Piacquadio on

Our garbage journey continues! On August 27 students made individual predictions about what will happen to the properties of the four rubbish materials (apple, banana, plastic, foil) over time. They also predicted what will happen to the weight of their landfill bottle over time. Half of the students had created a closed system and the other half had created an open systems.

I introduced the idea of system models, which they had used earlier. Scientists make system models to show the important components of the system and how those components interact. Students were asked to create a model that would include the system components and tell the story of what is going on in the bottles at each time point. Today we create the model for time point 1. The model for time point 1 includes a group prediction of what will happen to the rubbish materials.

On August 30 students examined one of the group’s models to notice its features. Models are thinking tools that scientists use to describe, explain, and predict. We will use our models to keep track of how the system changes. Later, we will use the models to support our explanations of the phenomenon.

Developing and using models is one of the science and engineering practices. We discussed how we are using these practices because we are scientists. Then we reviewed the list of 8 science and engineering practices:

  • Asking questions and defining problems
  • Developing and using models
  • Planning and carrying out investigations
  • Analyzing and interpreting data
  • Using mathematics and computational thinking
  • Constructing explanations and designing solutions
  • Engaging in argument from evidence
  • Obtaining, evaluating, and communicating information

We noticed which of these we have already used in science class. We have already used at least 3 of these!

We went back to our questions to pick another thing to investigate.

Our big question is How does the rubbish system work? One component of the rubbish system is a rubbish truck. What happens in a rubbish truck?

We watched this video clip about what happens in a garbage truck. The rubbish truck crushes materials. I asked What happens to materials when they are crushed? Does the kind of material change? Does the weight change? How could we investigate this in our classroom?

Students suggested we could weigh things before and after crushing them to see what happens to weight. Then we brainstormed ideas of what we could crush. Students contributed ideas and then we narrowed the list down to items that were things easy to get and safe. We decided on cardboard, paper, wood sticks, soda can, and aluminum foil.

The last activity for the day was an exit slip that asked students about the landfill bottle investigation. Students were asked to describe the system they were investigating, its components, the data they were collecting, and what questions the investigation will help answer. I collected these formative assessments.

Upon reviewing these assessments, I found that many students did not use the concepts of systems and components correctly yet. I plan to add an additional activity to reinforce this idea before we use systems again in class.

Model Landfill Bottles

Image from

On August 26 we started the major investigation of the unit. To answer the question of what happens to our garbage, students made six model landfill bottles. Students had collaboratively decided the components to include in the bottles the day before this activity. They included banana, apple, aluminum foil, and a plastic spoon in their bottles, along with soil and water. The spoons were identified as compostable spoons, which were the ones that come with the school lunches. Students will observe the bottles for a few weeks to look for changes in the properties of the materials over time.

I asked the students to predict what will happen to the materials in the bottles. Students said the materials would break down and turn into compost. I asked if they thought that would happen if the bottle were closed or open. Many students thought that the materials in the closed bottle would not break down. This gave a reason to compare open and closed systems. We left 3 bottles open to the air, but we did put a screen over the top of the bottle to prevent geckos from getting in the bottles. We closed the other three bottles. Now we have an open system and a closed system to compare. Systems and system models is a focal crosscutting concept for this lesson.

We have to wait to see what will happen. Next class we will create our group models for these systems.