Science Lesson Kit · Teacher Resource
Conservation of Matter — 5E Lesson Plan
Physical Science · 52 minutes
Grade 5
5E lesson flow
01
Engage
6 min
Teacher Does
Show salt crystals beside water, then show or demonstrate salt dissolved in water. Do not state the conservation rule. Ask whether the salt matter is gone and what measurement could settle the disagreement.
Students Do
Make a prediction and propose evidence that could test whether the total amount of matter changed.
Ask
- What changed that you can see?
- What would we need to measure before and after?
- Would measuring only the water be a fair comparison?
Look For
Students move from appearance-based claims toward measuring the same complete system.
02
Explore
17 min
Teacher Does
Guide groups to define the system boundary around the sealed bag and everything inside it. Have them measure, record, predict, mix without opening, remeasure, and record the scale precision.
Students Do
Measure the complete sealed system before mixing, tip the two cups inside the sealed bag to combine salt and water, gently mix, then measure the same complete system again.
Ask
- What exactly is inside our measured system?
- What must stay the same between the two measurements?
- If your measurements differ by 1 g on a scale that reads to the nearest gram, what should you do before making a claim?
Look For
Students include bag, cups, water, salt, and trapped air in both measurements; no material is intentionally added or removed.
03
Explain
10 min
Teacher Does
Graph several group results and introduce matter, mass, conserve, system, and evidence. Connect equal or very close results to the precision of the classroom scale.
Students Do
Compare before-and-after measurements, identify the class pattern, and build a claim supported by numerical evidence.
Ask
- Which numbers are your strongest evidence?
- Did the salt becoming hard to see tell us the total amount?
- Why might two readings differ by 1 g even when the system stayed closed?
Look For
Students say that the total measured amount was the same or very close within scale precision, rather than demanding perfect numerical equality.
04
Elaborate
12 min
Teacher Does
Use an open-system gas model and a closed-boundary comparison. Emphasize that gas is matter and that an apparent loss can occur if matter crosses the boundary and is not part of the final measurement.
Students Do
Trace which matter is inside or outside the measured boundary and explain why changing the boundary changes what the scale includes.
Ask
- Where is the gas after it crosses the open boundary?
- Did it stop being matter?
- How would you change the measured system to account for it?
Look For
Students distinguish conservation of matter from the mass remaining inside an open, changing measured system.
05
Evaluate
7 min
Teacher Does
Give a new sealed-system case such as melting ice or crushing a solid. Ask students to make a claim, cite before-and-after measurements, and state what the system includes.
Students Do
Complete a brief claim-evidence-reasoning response using a new context.
Ask
- What is your system boundary?
- Which measurement supports your claim?
- What changed, and what did not?
Look For
Students transfer the reasoning beyond dissolving and use quantitative evidence.
Student goal
I can use measurements and a system boundary to explain whether matter is conserved during a change.
Learning objectives
- I can measure and compare the mass of the same complete setup before and after a change.
- I can use numerical evidence and a system model to explain conservation of matter, including an apparent loss when matter leaves what is being measured.
Materials
- Digital classroom scale that reads to 1 g
- Sturdy quart-size freezer zip-top bag for each group plus one backup
- Two small lightweight plastic condiment cups per group
- About 60 mL room-temperature water per group
- About 15 g table salt per group
- Tray or shallow bin for each group
- Paper towel
- Student investigation recording sheet or science notebook
Before class
- Test each scale and identify its displayed precision (for example, nearest 1 g).
- For each group, place a small cup of water and a separate small cup of salt upright inside a sturdy freezer bag. Seal the outer bag completely before students measure.
- Keep the outside of each bag dry. Replace any bag that leaks; do not use leaking data as a conservation test.
- Students should not open the bag between the before and after measurements.
- Prepare a class data table for recording each group's before and after mass.
- Use the gas/open-system examples only as teacher-provided models or data. Do not run a sealed gas-producing reaction for this lesson.
Prior knowledge
- Matter has measurable mass.
- Students can read a classroom scale in grams.
- Students have seen materials dissolve, melt, mix, or break into smaller pieces.
Vocabulary
- matter
- Anything that has mass and takes up space.
- mass
- A measure of the amount of matter. In this lesson, the classroom scale reports mass in grams.
- conserve
- To keep the same total amount when all of the matter is accounted for.
- system
- The parts and materials included in what we choose to study and measure.
- physical change
- A change in form, state, size, or arrangement that does not mean matter was created or destroyed.
- mixture
- Two or more substances together. Mixing substances does not always mean a chemical reaction occurred.
- evidence
- Measurements or observations used to support a scientific claim.
Differentiation
- Provide a system-boundary sentence frame: “Our measured system includes ___.”
- Provide a claim-evidence frame: “The total mass was ___ g before and ___ g after, so the data support ___.”
- Let students work in pairs for scale reading while each student records and explains the evidence.
- Pre-label graph axes for students who need graphing support.
- For extension, ask students to compare two trials that differ by 1 g and explain why scale precision matters.
Assessment
- Check that students define and preserve the same system boundary before measuring.
- Check the investigation table for units, before/after measurements, and a comparison based on scale precision.
- Listen for students treating gas as matter and distinguishing matter leaving the measured system from matter being destroyed.
- Use the exit response to assess whether the student cites numbers rather than appearance alone.
Exit ticket
A sealed container is 243 g before a physical change and 242 g after on a scale that reads to the nearest gram. What should you check, and what evidence would you need before deciding whether the total amount of matter changed?
Extension
Design a measurement plan for an open-system situation. Show where you would place the system boundary so matter that could leave is still accounted for.