Mississippi Science PHS.4.2
The Standard
- PHS.4
- Students will analyze changes in matter and the relationship of these changes to the law of conservation of matter and energy.
Design and conduct investigations to produce evidence that mass is conserved in chemical reactions (e.g., vinegar and baking soda in a Ziploc© bag).
2026 Mississippi College- and Career-Readiness Standards for Science · The Law of Conservation of Matter and Energy
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students plan and run a reaction in a sealed container. They weigh the whole container before and after, record the readings, and use them to decide whether the total mass changed.
What Mastery Looks Like
- A student keeps the baking soda and vinegar apart until the bag is sealed. They weigh the entire bag before and after mixing, then explain why the gas must stay inside for the test to work.
Common Misconceptions
- Students may think gas has no mass or that bubbling creates new matter. They may also treat a lower reading from a leaking bag as proof that matter was destroyed.
How to Assess It
- Exit ticket: Sketch a sealed-bag vinegar and baking soda test. Label what you would weigh before and after mixing, and explain what matching readings would show.
Lesson moves
Ways to Teach It
Put vinegar in a small cup inside a bag with baking soda beside it; seal, weigh, tip the cup, and weigh again.
Show a photo of an inflated reaction bag and ask, "Did its mass change? What measurement would settle that?"
Give pairs before-and-after mass cards for sealed and leaking bags; have them sort which readings support a sound conclusion.
Weigh a capped soda bottle, open and recap it, then reweigh and compare escaping gas with gas trapped in the reaction bag.
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Printable PHS.4.2 Worksheet
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