Conservation of Mass NGSS MS-PS1-5


In the Conservation of Mass mini unit, students practice counting atoms in chemical formulas and review why we cannot turn carbon into gold! They demonstrate the law of conservation of mass by comparing the reactants and products of rust. Kids then model the reaction between baking soda and vinegar by cutting apart reactant molecules, building the products and creating a poster of this chemical equation.


Extension activities include baking a cake in a mug to further explore the law of conservation of mass!

Anchor Phenomenon Ideas: Start this unit with a chemical reaction in a bag! You can demonstrate for the class or have students complete the quick lab with you. Detailed instructions are here. Mix one tablespoon calcium chloride and one teaspoon baking soda in a Ziploc bag. Then place a small paper cup with ten ml phenol red indicator in the bag. Push extra air out and seal the bag. Then, tip the phenol red into the powder and look for a temperature change, gas formation and color change.

Lead a discussion with your students and use their questions to make connections throughout your unit. Then, return to this reaction and measure the mass of the bag before and after the chemical reaction. Challenge your students to write a balanced chemical equation for this reaction.

Tips and Tricks: Some students love balancing equations - it's like a puzzle to solve - but others do not enjoy the challenge. The PhET simulation Balancing Chemical Equations is a helpful tool to practice.

Remind students that balanced equations demonstrate the law of conservation of mass and model the breaking of old bonds and the forming of new bonds in chemical reactions with molecular model kits like this one.

Enrichment Ideas: Challenge your students to learn more about the chemistry of cooking! This American Chemical Society site is a great place to get started. Check out their video about why pizza tastes so good.

Then, challenge kids to design an investigation to learn the difference between baking soda and baking powder. Which one should you use for your favorite cookie recipe and why?