Mixing Matter

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SWBAT prove that the overall mass/weight of two substances is conserved, even when the two substances are mixed together.

Big Idea

In this lesson, students investigate the overall mass of gravel and sand before and after they are mixed together.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at Edudemic.com, How Inquiry-Based Learning Works with STEM, very clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will begin by exploring the properties of matter. Then, the class will investigate the mass of matter before and after physical and chemical changes by conducting investigations and constructing graphs. 

Summary of Lesson

Today, I open the lesson by defining and discussing the meaning of mixtures. Students then explore how the overall mass of sand and gravel does not change when they are mixed together. At the end of the lesson, students reflect and apply their new understanding of the mass of mixtures by constructing a graph and drawing conclusions. 

Next Generation Science Standards  

This lesson will support the following NGSS Standard(s):

5-PS1-2. Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved.

Scientific & Engineering Practices

For this lesson, students are engaged in Science & Engineering Practice:

Science & Engineering Practice 3: Planning and Carrying out Investigations

Students conduct and investigation and measure the mass of gravel and sand before and after mixed. 

Crosscutting Concepts

To relate ideas across disciplinary content, during this lesson I focus on the following Crosscutting Concept

Crosscutting Concept 5: Energy and Matter 

Students prove that matter is conserved, even when two substances are mixed together. 

Disciplinary Core Ideas

In addition, this lesson also aligns with the following Disciplinary Core Ideas

PS1.A:  Structure and Properties of Matter

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. A model showing that gases are made from matter particles that are too small § to see and are moving freely around in space can explain many observations, including the inflation and shape of a balloon and the effects of air on larger particles or objects. (5-PS1-1)

The amount (weight) of matter is conserved when it changes form, even in transitions in which it seems to vanish. (5-PS1-2)

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of two or three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half or thirds. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  


20 minutes

Matter Unit Lapbooks

To provide students with a method to keep track of their research and thinking during our unit on matter, I followed these steps to create lapbooks for each student. 

1. I folded each side of a file folder inward to create a booklet that opens from the center: File Folder.

2. Next, I made copies of Lapbook Templates on colored paper (purple, yellow, green, and orange). I made sure to have enough copies so that each student would have 4 graphs, 6 research notes, 8 investigations, 18 vocabulary words (9 sets of 2 words), and the 4 pictures.  I also copied the Other Research Pocket onto blue card stock paper so that students would have a place to put loose papers. 

3. Then, I stapled the templates into each lapbook: Inside the Lapbook.

4. Before starting our unit on matter, I asked students to help personalize their lapbooks. Students used a glue stick and tape to secure the blue research pockets on the back (Student Research Pocket Example). Then, they decorated the cover: 


Creating these lapbooks helps build excitement and student ownership!


Teacher Note: This demonstration is inspired by the brain-teaser, Which weighs more, a ton of feathers or a ton of bricks? (Both weigh the same... one ton)

I want to encourage interest in today's lesson and capitalize on student curiosity, so I hold up two cups and explain: One cup has 150 grams of gravel and the other cup has 150 grams of sand (150 Grams of Gravel & 150 Grams of Sand). I pose the following "trick" question: Which cup has more mass/matter? Even though I told students that they both have a mass of 150 grams, some students think the gravel has more mass/matter because the gravel is bigger. Others think the sand has more mass/matter because there are more particles. Then there are some students who think they have the same amount of mass/matter: Gravel & Sand Discussion.


Today, we will be adding another word to the vocabulary section of our lapbooks: mixture. I explain as students record the meaning of a mixture (Mixture): a combination of two or more substances that are not chemically united. We then discuss examples of mixtures in our daily lives, such as a Mixture of Erasers & Paper Clips, making a chex snack mix, or mixing oil with water. One student asks about baking. Proudly, I see students using their resources and referring to the Physical & Chemical Changes Poster from two lessons ago, Changing the Shape of Matter. They point out that baking chemically changes the ingredients to form a new substance. 


40 minutes

Investigation Overview

According to NGSS Standard 5-PS1-2, students are expected to "Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved." For today's investigation, students will measure the mass of a cup of gravel and a cup of sand. Then, they will mix the sand and gravel together to find that the overall mass of the gravel and sand remained the same. Students will end up having to take the mass of the cups into consideration as well. Some students mix the sand and gravel (Mixture of Gravel & Sand) and then they will figure out that they have to "double cup the mixture." Others will place the sand cup on top of the gravel cup and measure the mass without stirring (Measuring Sand & Gravel Together without Mixing).

Getting Ready

To prepare for today's investigation, I set out the following items on the counter: 

Today, each group will be given 1 Cup of Gravel, 1 Cup of Sand, & 1 Spoon. Here's what you'll be doing! First, you'll find the mass of the gravel and the mass of the sand. Then you'll create a sand and gravel mixture by using the spoon to stir the sand and gravel together. Finally, you'll find the mass of the gravel and sand mixed together. I wonder if the overall mass of the sand and gravel will change.... 

Investigation Template

The class discusses and completes a new investigation template in their lapbooks: Question & Observations (Before).

Question: Does mixing sand and gravel change the overall mass?

Observations (Before): Students draw a diagram of one cup of sand and one cup of gravel. Then, they point out that they are in the same cups, but that they represent two different substances. 

We also create a Data Table so that students have a place to record the results of their investigation. Students agree that they would like to measure the mass of the gravel, then the mass of the sand, and finally, the sand and gravel mixture altogether.

Just as I had hoped, one student also points out that students will need to measure both cups as well: (1 cup + gravel) + (1 cup + sand) = (2 cups + gravel & sand).

Monitoring Student Understanding

Once students begin working (Students Measuring the Mass of Sand), I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. What have you found so far? 
  4. Has your thinking changed? 
  5. What evidence do you have? 
  6. How did you decide _____?
  7. What conclusion can you draw about ____?

Student Conferences

During this conference, Conferencing with Students, I talk to the students about the importance of calibrating the scale. We also discuss how the students might double check their investigation findings by subtracting the mass of the sand or gravel from the total mass of the sand and gravel mixture. 

Reflect & Apply

30 minutes

Sharing Findings

Now that students have built meaning and understanding by observing, questioning, and exploring, it is important to provide students with the opportunity to share their findings. For this reason, I invite students to discuss their results as a class: Class Discussing Results. This is an important conversation to have before students write their investigation conclusions. Otherwise, some students might conclude that there was actually a change in mass when ice melts when this change was due to inaccurate scales, placement of the bag/mass weights on the platforms, or leaking bags!

Drawing Conclusions

I invite students to use their data and our class discussion to write the conclusions to their investigations. Here's an example of a completed investigation: Sand & Gravel Investigation.

At first several students concluded, "I can conclude that the mixture of sand and gravel has more mass." However, the goal of this investigation was to analyze the overall mass of the sand and gravel (separated and then mixed together). 

Through more modeling (please see the reflection) and discussion, more and more students began to see the purpose of this investigation!

In particular, using one group's data as an example really helped to clear everything up. They shared out that the mass of their gravel was 143 grams and the mass of their sand was 117 grams. The mass of the sand and gravel mixture was 260 grams. We wrote this as an addition problem on the board (Example of Adding on the Board), used a digital scale to double check (Checking the Overal Mass Using a Digital Scale), and then students began to see how the overall mass does not change even when two substances are mixed together! 

Soon, other groups also wanted to double check their measurements using the digital scale: Using a Digital Scale.


According to NGSS Standard 5-PS1-2, 5th grade students are expected to "measure and graph quantities to provide evidence that regardless of the type of change that occurs, the total weight of matter is conserved." For this reason, I ask students to complete a graph template in their lapbooks to represent their findings. 

We discuss how to label the x-axis with "Substances" and the y-axis with the "Mass." I then remind students how to determine the scale of their individual graphs using the highest data collected. For example, if their highest data point is 235 grams, they want to make sure that the scale counts by a number that allows them to graph up to 235 grams. Most students love graphing and can't wait to begin! 

Here are a couple examples of student graphs: