Name: ________________________________
Period: _____
Conservation of Mass Lab
The Law of Conservation of Mass states that mass in a closed system will remain
constant, regardless of the processes acting on the system. A closed system is one to
which nothing can be added or taken away.
Procedure:
1. Record the mass of an empty beaker using the digital scale or triple beam balance.
2. Add a set volume of water to the beaker (record the volume of water added and mass of the water).
3. Record the mass of an Alka Seltzer tablet.
4. Add the Alka Seltzer tablet to the beaker with water, and wait for all fizzing to stop.
5. Record the volume of water in the beaker.
5. Record the mass of the the beaker and its contents.
Data Collection:
Do this column BEFORE the experiment
starts:
Mass of empty beaker: __________
Do this column AFTER the experiment is
finished.
Ending volume of water after fizzing has stopped:
_______
Mass of beaker + water: ___________
Mass of beaker + water + Alka Seltzer: _____
Mass of water: ___________
Volume of water: __________
Mass of alka seltzer tablet: ___________
Using the masses recorded above, calculate the
following:
Mass of beaker + water + Alka Seltzer: _____
Questions:
1. Is the ending mass of the beaker, water, and alka seltzer exactly equal to the calculated starting mass of the
beaker, water, and Alka Seltzer? ________________________________
2. Restate the Law of Conservation of Mass in your own words:
____________________________________________________________________________
____________________________________________________________________________
3. According to the Law of Conservation of Mass, the starting and ending mass of the ingredients should be
exactly the same. Give your best explanation or guess as to why the masses are different in this situation?
____________________________________________________________________________
____________________________________________________________________________
Aker-CJH-Fall 2004
Name: ________________________________
Period: _____
4. Is the starting volume of liquid and ending volume of liquid the same? ______ Explain why. _________
____________________________________________________________________________
____________________________________________________________________________
5. Do you think the system in this lab is a closed or an open system? Explain.
____________________________________________________________________________
____________________________________________________________________________
6. If you were to measure the mass of an Alka Seltzer tablet and leave the tablet sitting for a day, and measure
its mass again, would you expect the two masses to be equal? __________ What is different about the
situation in this lab?
____________________________________________________________________________
7. Has a chemical reaction occurred in this lab? ________ How do you know? ___________________
___________________________________________________________________________
8. If you think a chemical reaction occurred in this lab, does this explain why there was a change in mass at the
beginning of the experiment? ________ Why or why not? __________________________________
____________________________________________________________________________
____________________________________________________________________________
Make sure you have put the appropriate standard metric units after your answers where appropriate!
Aker-CJH-Fall 2004