Mississippi Science P.7.5E.1
The Standard
- P.7.5E
- Students will demonstrate an understanding of the law of conservation of mass.
Conduct simple scientific investigations to show that total mass is not altered during a chemical reaction in a closed system. Compare results of investigations to Antoine-Laurent Lavoisier’s discovery of the law of conservation of mass.
2026 Mississippi College- and Career-Readiness Standards for Science · Organization of Matter and Chemical Interactions
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students weigh a sealed bag holding baking soda and vinegar, then mix them without opening it. They weigh it again and explain why the bubbles do not change its mass. They compare their measurements with Lavoisier's work in sealed containers.
What Mastery Looks Like
- Students record starting and ending masses that match within the scale's precision. They explain that the gas stays in the bag and connect their measurements to Lavoisier's results.
Common Misconceptions
- Students may think bubbles have no mass, so a bubbling reaction must weigh less afterward. They may take a lower mass in an open cup, where gas escapes, as proof that mass was destroyed.
How to Assess It
- Exit ticket: A sealed bag weighs 32.4 g before a reaction and 32.4 g after it bubbles. Where is the gas, and how does this result compare with Lavoisier's measurements?
Lesson moves
Ways to Teach It
Put vinegar in a small cup inside a zip bag with baking soda, seal and weigh it, tip the cup, then weigh again.
Ask partners why an open cup might weigh less after bubbling, then have them compare the sealed bag's result with Lavoisier's.
Hand out cards showing sealed (50 g to 50 g) and open (50 g to 48 g) reactions; pairs identify where gas went.
Weigh a glow stick before and after snapping it, then ask why its mass stays the same as the chemicals react inside.
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- PHS.4.2
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