ALEX Lesson Plan


Changing Matter, Not Weight

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  This lesson provided by:  
Author:Kathy Perkins
System: Tuscaloosa City
School: Tuscaloosa City Board Of Education
The event this resource created for:ASTA
  General Lesson Information  
Lesson Plan ID: 34772


Changing Matter, Not Weight


Matter is not created nor destroyed; it simply changes from one form to another.  This law of conservation of mass challenges elementary students’ ideas about matter, because many children may think that matter is created or destroyed in a chemical reaction.  In this lesson, students will challenge their preconceptions about matter by experimenting with physical and chemical changes to determine that the total weight of the matter does not change. Students will use math to show that the total weight of matter is equal to the sum of the weight of its component parts, and they will graph this information to show that the weight of matter is conserved during physical and chemical changes.

This lesson results from a collaboration between the Alabama State Department of Education and ASTA.

 Associated Standards and Objectives 
Content Standard(s):
SC2015 (2015)
Grade: 5
2 ) Investigate matter to provide mathematical evidence, including graphs, to show that regardless of the type of reaction (e.g., new substance forming due to dissolving or mixing) or change (e.g., phase change) that occurs when heating, cooling, or mixing substances, the total weight of the matter is conserved.

NAEP Framework
NAEP Statement::
P4.1: Objects and substances have properties. Weight (mass) and volume are properties that can be measured using appropriate tools.*

NAEP Statement::
P4.3: Matter exists in several different states; the most common states are solid, liquid, and gas. Each state of matter has unique properties. For instance, gases are easily compressed while solids and liquids are not. The shape of a solid is independent of its container; liquids and gases take the shape of their containers.

NAEP Statement::
P4.6: One way to change matter from one state to another and back again is by heating and cooling.

Unpacked Content
Scientific And Engineering Practices:
Using Mathematics and Computational Thinking
Crosscutting Concepts: Scale, Proportion, and Quantity
Disciplinary Core Idea: Matter and Its Interactions
Evidence Of Student Attainment:
  • 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.
Teacher Vocabulary:
  • Quantitative measurements (mass, weight, standard unit)
  • Physical quantities (weight, time, temperature, volume)
  • Property changes
  • Matter
  • Reaction
  • Heating
  • Cooling
  • Mixing
  • Physical properties
  • Conservation of matter
  • Graphing
Students know:
  • The amount (weight) of matter is conserved when it changes form, even in transitions in which it seems to vanish.
  • No matter what reaction or change in properties occurs, the total weight of the substances does not change. (Boundary: Mass and weight are not distinguished at this grade level.)
Students are able to:
  • Measure and graph the given quantities using standard units, including: the weight of substances before they are heated, cooled, or mixed and the weight of substances, including any new substances produced by a reaction, after they are heated, cooled, or mixed.
  • Measure and/or calculate the difference between the total weight of the substances (using standard units) before and after they are heated, cooled, and/or mixed.
  • Describe the changes in properties they observe during and/or after heating, cooling, or mixing substances.
  • Use their measurements and calculations to describe that the total weights of the substances did not change, regardless of the reaction or changes in properties that were observed.
  • Use measurements and descriptions of weight, as well as the assumption of consistent patterns in natural systems, to describe evidence to address scientific questions about the conservation of the amount of matter, including the idea that the total weight of matter is conserved after heating, cooling, or mixing substances.
Students understand that:
  • Standard units are used to measure and describe physical quantities such as weight and can be used to demonstrate the conservation of the total weight of matter.
AMSTI Resources:
AMSTI Module:
Matter and Interactions

Alabama Alternate Achievement Standards
AAS Standard:
SCI.AAS.5.2- Recognize that regardless of the type of reaction (e.g., new substance forming due to dissolving or mixing) or change (e.g., phase change) that occurs when heating, cooling, or mixing substances, the total weight of the matter is conserved.

Local/National Standards:


Primary Learning Objective(s):

Students will draw conclusions based on evidence from investigations to support the conservation of weight of matter after a physical or chemical change. 

Additional Learning Objective(s):

Students will:

  • Identify the parts in a system.
  • Weigh objects using balances.
  • Calculate the weight of a system by adding the weights of its component parts.
  • Graph data.
  • Draw conclusions based on evidence from their investigations that show that the total weight of a closed system does not change during a physical or chemical change.
 Preparation Information 

Total Duration:

Greater than 120 Minutes

Materials and Resources:

Teacher materials for introductory demonstration:

  • paper
  • matches or lighter
  • metal bowl

Student materials needed for each group of 4 students:

  • balance.  You may use bucket balances and gram weights or simple scales.  If gram weights are not available, you can use pennies as increments of weight measurement. A penny weighs 2.5 grams.
  • Small (approx.. 10” square) piece of cardboard
  • Ice cube in a Ziploc bag (Students can reuse this bag of water later in the final part of the lesson.)
  • One paper or plastic cup filled halfway with water
  • Sugar packet
  • 10 – 12 linking cubes or Lego bricks
  • Effervescent antacid tablet
  • Empty water bottle
  • Vinegar
  • Baking soda
  • Measuring cup or graduated cylinders
  • Teaspoon
  • Funnel
  • Balloon

General classroom materials:

  • chart paper or marker board
  • markers
  • square sticky notes in two colors

Technology Resources Needed:

Optional: computers with access to Google Apps (Students may use Google Sheets to create graphs in the extension portion of the lesson; this requires students to have Gmail addresses.)


Teachers should have a clear understanding of the law of conservation of mass and the difference between physical and chemical changes.


Engage (10 minutes):

Show students a piece of paper and say there are many ways to change it.  Some involve physical changes (rip paper into pieces) that change the form of the paper without changing it into a different substance, and some involve chemical changes (burn one of the pieces over a metal bowl) where the particles of paper change into different substances (smoke and ash). 

Ask the essential question: When matter changes, is the total amount of matter increased, decreased, or does it stay the same?  Today we will experiment to find out. 

Have each student write his name on a yellow sticky note and post it on the class chart to make a bar graph of the students’ predictions. (See Attachment section for a sample graph.  Students will have the opportunity to change their answers based on evidence from their investigations at the end of the lesson.)

Explore (20 minutes):

Have students use the chart on the note-taking guide (see Attachment section) or create a chart in their notebooks with columns for Material, Weight Before Change, Type of Change, Prediction, Weight After Change, and How Weight Changed.  Have students work in groups of four to collect materials and make changes.

Materials needed for each group:

  • Small (6” - 10” square) piece of cardboard
  • Ice cube in a Ziploc bag
  • One paper or plastic cup filled halfway with water
  • Sugar packet
  • 10 – 12 linking cubes or Lego bricks
  • Balance
  • Gram weights

Within their groups, have students discuss different ways they could change each of the materials.  For example, they can let the ice in the plastic bag melt or hit it with a hammer to break it into pieces.  They can rip or fold the cardboard. They can assemble the cubes or Legos to make many different structures.

Have each group predict whether changes made to the materials will increase, decrease, or not affect the total weight of the matter.  (Students may also predict that different changes will affect the total weight in different ways.) 

You may allow students to choose which changes they want to make with each type of matter, or you may guide them to make the following physical changes:

  • Melting ice
  • Tearing cardboard
  • Building cube or Lego structure
  • Dissolving sugar in water

As students investigate, circulate to ask them how they are making sure they are weighing all the matter involved in the original change and none from outside the change.  For example, students will weigh the sugar packet and cup of water before they dissolve the sugar in water.  After the sugar is dissolved, the final weight must include the weight of the cup with the solution and the empty sugar packet. Since the paper packet has some weight that is included before the change, it must also be included as part of the system after the change.  Condensation that appears on the outside of the bag of melted ice should be wiped off before weighing the bag of water since this water comes from the air and not the ice cube. 

Students should record information in their data tables as they investigate.  After completing the four changes, have students make generalizations about the weight changes during changes in matter (the total weight does not change).  Introduce term conserved (which means the total quantity stays the same).  Have students write down this definition and use the word in a sentence to explain how this term applies to their investigations (The total weight was conserved during all the changes.)

Explain (30 minutes):

Have students weigh the different pieces in one of the part-to-whole changes (the ripped cardboard or the individual Lego blocks or cubes.)  Ask students how the weight of these parts relates to the weight of the whole piece of cardboard or block structure.  (The total weight of a system is equal to the sum of the parts of the whole.) Have students work together in their groups to answer these questions:

  • How can we represent this as an equation? Weight of Part 1 + Weight of Part 2 + Weight of Part 3 + Weight of Part 4 = Total Weight After Change 
  • How can we show this in a bar graph?  Model how to construct a bar graph in which each the measurements for each part are stacked to show the total weight.  (Click here for a sample graph of the part-to-whole relationship.)

Most students will understand that these physical changes do not change the total amount of matter present, but is the same true for chemical changes?

Mix vinegar and baking soda in a water bottle and have students observe what happens.  (It fizzes.)  Have students explain what causes the bubbles. (As the two substances mix, a gas is released.) Ask students whether they think the total weight of the matter changed in this reaction.  Tell them they will investigate to confirm or refute their predictions. 

Explain the procedure: In order to figure out whether the total amount and weight of matter changes during a change, we must have a closed system.  A system is a group of parts that works together to form a whole.  Refer students to the burning paper demonstration.  What were the parts of this system? (The paper, the lighter, and the bowl.)  How did these parts work together to make a change? (The lighter made a flame that ignited the paper, and the bowl caught the ashes the paper burned.)  Was this a closed system? (No, because the smoke and gases released went into the air; it was not enclosed in anything.)  Why do you think it is important for the system to be closed when we are trying to find out if the total weight changes?  (If some of the matter escapes into the air, then we can’t measure it all.)

Ask students: How can we create a closed system to include the gas released by the vinegar and baking soda reaction?  (Put a balloon over the top of the bottle to trap the gasses.) 

Model how to mix baking soda and vinegar to capture the gas released by the reaction.  Measure the weight of the balloon, and then pour one teaspoon (5 mL) of baking soda into a balloon using a funnel.  Measure the weight of the balloon filled with baking soda.  Ask students how we could figure out the weight of the baking soda.  Why don’t we just weigh the baking soda by itself? (It would make a mess; we might spill some of it when pouring it in the balloon and then our measurements would not be accurate.)

Measure ¼ cup (approx. 120 mL) of vinegar and pour it into the water bottle using the funnel.  Measure the weight of the water bottle and vinegar.  Carefully stretch the open end of the balloon around the top of the water bottle, making sure to hold the balloon so no baking soda falls into the bottle.  Measure the weight of the entire system.  Write the weight of the total system as sum of the parts (weight of water bottle with containing vinegar + weight of balloon containing baking soda = weight of total system.)  Do you think the weight will remain the same once you lift the balloon to mix the baking soda falls into the vinegar?  Have students test their predictions in small groups and discuss the following questions:

  • Is more matter present now than before we mixed the vinegar and baking soda? Why?
  • Has the weight of the matter (which includes the bottle, balloon, and all contents) changed?  Why not?
  • What generalizations can we make about changes in weight during changes in matter?
  • What do you think would happen to the weight of the water bottle and baking soda if we did not trap the gas released in a balloon?

Have students make bar graphs to show the sum of the weight of the parts of the vinegar and baking soda bottle system equals the total weight of the system both before and after the reaction. (See sample.)

Elaborate (30 minutes):

Have students plan their own experiment to test the weight and graph the changes in another chemical reaction: mixing an effervescent antacid tablet with water in a plastic bag.  Students can reuse the bag of water from the melted ice cube.  They should measure the weight of the tablet and the bag of water, noting the weight of each of these parts before allowing them to mix.  They should hold the tablet in the corner of the bag and zip it closed.  Once the bag has been sealed, students can drop the tablet into the water and observe the bag inflating due to the gasses released during the reaction.  Have them measure the final weight of the bag and all its contents following the reaction.  Students should graph the results and use their data as evidence to support the claim that matter is not created or destroyed in a closed system, so the total weight of the reactants stays the same.  

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Assessment Strategies

Evaluate students' written explanations and use of graphs and data to support the law of conservation of mass using this rubric.


  • Have students use Google Sheets to record measurement data and make different types of graphs (a Google account is required.)
  • Have students research the difference between physical and chemical changes on Chem4Kids and plan two new tests for the law of conservation of mass, one that is a physical change and one that is a chemical change. 


  • Consider individual student needs when assigning small groups for the lesson.  Pair students who need extra help with peer tutors.
  • Have students preview or review lesson by watching this video.

View the Special Education resources for instructional guidance in providing modifications and adaptations for students with significant cognitive disabilities who qualify for the Alabama Alternate Assessment.