* Problem/Purpose * Background Information: The Law of Conservation of Mass was created by Antoine Lavoisier in the 18th century. This law stated that mass could matter could neither be created nor destroyed. During a reaction the bonds of the reactants are broken and form new substances. As stated in the Law of Conservation, matter can neither be created nor destroyed; because of this the products should have the same number and type of atoms as seen in the reactants. * Purpose: Test the Law of Conservation of Mass.
* Hypothesis: If we weight the mass of the materials before and after the reaction, then we can prove if the Law of Conservation of Mass is true.
* 25mL graduated cylinder
* 2 resealable bags
* Antacid tablet
* CaCl2 , Calcium Chloride
* NaHCO3 , Sodium Hydrogen Carbonate
* Universal Indicator
1. Measure 25mL of water and put into a resealable bag. Flatten air out of the bag and seal it. Record the mass in Table 1. 2. Record the mass of the antacid tablet in Table 1 3. Tip the bag sideways, and while holding the bag this way, add the tablet and water so not mix. Do not trap any extra air in the bag. Reseal the bag. 4. Let the tablet drop into the water. Observe the reaction until it comes to a complete stop. Record the observations. 5. When the reaction is complete, record the mass of the bag and its contents in Table 1. Part B
6. Add two scoops of CaCl2 to the second bag 7. Add one scoop of NaHCO3 to the bag and shake gently to mix. 8. Determine the mass of the bag and its contents. Record in Table 2. 9. Measure 25mL of water in a graduated cylinder. Add 10 drops of Universal Indicator to the water. 10. Tip the bag sideways, and while holding the solids in the upper part of the bag, pour the water into the bag so the solids don’t mix. 11. Keeping the trapped air to a minimum, reseal the bag. Hold the bag and let the liquid move from one end of the bag to the other until the contents are mixed. 12. Observe the reaction until it comes to a complete stop. Record your observations 13. Record the mass of the unopened bag in Table 2. Clean up your work and wash your hands before leaving the laboratory.
Table 1: Antacid and Water|
Mass of bag and water| 27.085g|
Mass of tablet| 3.21g|
Mass of bag and reactants| 30.305g|
Mass of bag and products| 28.14g|
Table 2: CaCl2, NaHCO3, and Water|
Mass of bag and dry reactants| 4.09g|
Volume of water| 25mL|
Mass of water| 24.925g|
Total mass of bag and reactants| 29.015g|
Mass of bag and products| 27.37g|
A. Analysis Questions:
1. How do the values for the total mass before and after each reaction demonstrate the law of conservation of mass? The values seem to be in the same general value 2. What were three observations you made that indicated a reaction had occurred in part A? The tablet started to fizz, the bag began to fill with gas, and you could hear the tablet reacting with the water. 3. An indicator changes color when the acidity of a solution changes. What evidence is there that such change occurred in Part B? The universal indicator changed to a yellowish orange color 4. Did the reaction in Part B become more acidic or basic? More acidic
B. Conclusion: The lab showed us that the Law of Conservation of Mass is correct. I feel that there were some mistakes in the lab. The size of the scale we were using was not large enough to fit the entire bag on for weighing. I feel that this affected the results we recorded for mass. If I were to redo this experiment I would be sure to use a bigger scale. I feel the data was also affected by extra air left in the bag. The results are close enough to show that the Law of Conservation of Mass is possible though when you take into accounts the problem we had with the lab.