Conservation of Mass (Dakota Pollock)
Title: Law of Conservation of Mass
Principle(s) Investigated: Matter is neither created nor destroyed in chemical processes.
During a chemical reaction, bonds are broken and reattached to make new molecules.
Matter is made of atoms that rearrange to make molecules.
Standards: PS 1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
PS 1-5: Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.
Materials: Alka-seltzer tablets, balloon, water, flask, zip lock bag, scale, small cup
Procedure:
- Fill flask with water until 1/3-1/2 full.
- Weigh flask + water and record on data table.
- Weigh balloon and record mass on data table.
- Weigh total amount of Alka-seltzer tablets to be used and record on data table.
- Crush tablets enough to put them into the balloon.
- Seal balloon around mouth of flask.
- Maneuver contents of balloon into flask to mix with water.
- Record observations, and weigh as soon as maximum balloon size is reached... About 3-7 seconds after tablets mix with water. Record final mass.
Student prior knowledge: Students need to understand that matter is neither created nor destroyed, which is the Law of Conservation of Mass. They will be expected to understand the difference between theory and law, which is why this principe can be applied to all chemical reactions. Further understanding will need to come from their understanding what a chemical equation represents. For instance, reactants are on the left side, the arrow represents a rearrangement of the reactants to form the products. They will need to understand that no new atoms were added to or taken away from the reactants, and that the same number of atoms of each element exist on the left side as the right side.
Explanation: Students are able to see the effects of a chemical reaction physically. The balloon will fill up and inflate once the tablets are mixed with water because it catches the gas which is a product of the reaction. The goal is for them to end up with the same mass as they started with, but this is also a good opportunity to discuss why they may not have gotten equal initial and final masses--i.e. user error with the scale, gas being released because the balloon is not completely sealed.
Questions & Answers:
1. Explain whether the results of your experiment support of refute the law of conservation of mass.
2. If someone's change in mass was not zero, does that mean that the law of conservation of mass is wrong? Explain with examples.
3. If you were to do this experiment again, what would you change in your procedure or method to elicit more exact results that align as close as possible to the law of conservation of mass?
Applications to Everyday Life:
1. When matter changes its state, it often takes up a different volume and looks like there could be more or less of it than what was started with, however state change does not alter mass.
2. When cooking or baking, the ingredients sometimes change shape or texture, and the law of conservation of mass applies here as the molecules are rearranged, lost as vapor when boiling or instance, or wet ingredients absorbed into dry, etc.
3. The mass of nature itself is constant. All of the earth's systems interact chemically, biologically and physically, but in all of these reactions and interactions the total mass of nature is conserved.
Photographs:
Videos:
https://www.youtube.com/watch?v=nySmILuRVTY
