Mississippi Science P.7.5E.2
The Standard
- P.7.5E
- Students will demonstrate an understanding of the law of conservation of mass.
Analyze data from investigations to explain why the total mass of the product in an open system appears to be less than the mass of reactants.
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 compare mass measurements before and after a reaction in an open container. They use the drop in measured mass to explain that gas formed and escaped.
What Mastery Looks Like
- A student can calculate how much mass the open setup lost. They can explain why the reading dropped even though the matter did not disappear.
Common Misconceptions
- Students may think fizzing destroys matter. They may count only the liquid left in the cup and forget that the gas is also a product.
How to Assess It
- Exit ticket: An open cup weighs 105 g before a fizzing reaction and 102 g after. How much mass escaped, and where did it go?
Lesson moves
Ways to Teach It
Place vinegar and baking soda in separate cups on one scale, record the mass, combine them, then weigh both cups after fizzing.
Show a 3 g mass drop after fizzing in an open cup; ask students to write where the missing mass went.
Give pairs before-and-after mass cards to sort into open and sealed setups, then calculate the mass lost from each open setup.
Weigh a sealed soda bottle, open it to release gas without spilling, then recap and weigh it again.
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Related Standards
- P.7.5D.1
Analyze evidence from scientific investigations to predict likely outcomes of chemical reactions.
- CHE.6.3
Use mathematics and computational analysis to represent the ratio of reactants and products in terms of masses, molecules, and moles (stoichiometry).
- P.7.5E.1
Conduct simple scientific investigations to show that total mass is not altered during a chemical reaction in a closed system. Compare results of investigations...
- P.5.5C.3
Analyze and interpret data to support claims that when two substances are mixed, the total weight of matter is conserved.
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