How Does The Lock Bag Experiment Demonstrate The Law Of Conservation Of Mass?

Law of Conservation of Mass Experiment CER
Question: Does a controlled (closed system) zip lock bag experiment demonstrate the Law of Conservation of Mass?
Claim
In our class we did an experiment where we put different known supstances into a ziplock bag and closed the bag, that way we could achieve a closed experiment and attemp to support The Law of Conservation of Mass. The Law of Conservation of Mass states that mass can neither be created nor destroyed in a closed system. According to my data in the ziplock bag experiment, it supported the Law of Conservation of Mass because before the experiment our total of all the substances added to 32.3g before and after the experiment.

Evidence

Name
Mass (g) Before
Mass (g) After
Mass (g) Difference

Where as the other 50% of the groups did not support the Law of Conservation of Mass. The data that my group collected supported the Law of Conservation of Mass, as our substances stayed the same weight before and after in the closed experiment. Out of the 4 groups on my table 4 out of 4 or 100% of the groups supported The Law of Conservation of Mass.

On the graph, you can tell that there was a chemical reaction that took place because there was an exothermic reaction. The temperature started rising right away, which is when the reaction started to take place. The beginning temperature of the substances used was between 21∘C and 22∘C. By 90 seconds into the experiment the temperature was at 72∘C. Immediately after 90 seconds the experiment had ended because then the temperature of the mixed substance was decreasing to go back to room temperature where it started. The final temperature that my group took was 33∘C at 8 minutes and 12 seconds.

In this experiment my group “supported” The Law of Conservation of Mass because, in our closed system experiment the mass didn't change. For this experiment we had to calculate the mass of all of the materials that we used along with the bag before the experiment occurred. After the experiment the groups had to take find the mass of the bag and the substances. During this experiment you had to have the ziplock bag closed to make sure that none of the substances, if turned into gases, would be contained in the bag. For that reason the mass should stay the same as stated in the Law of Conservation of Mass. We had to mix baking soda, calcium chloride and water and then as a product we would have rocksalt and calcium carbonate, 2NaHCO₃+CaCl₂===>CaCO₃+CO₂+2NaCl+H₂O. We know that a chemical reaction took place because on the products into reactants equation the elements are equally transfered from one side to the other after the chemical reaction took place. We were given a plastic bag, that way we could do a closed experiment. We had to support that there were endothermic and exothermic reaction and that The Law of Conservation of Mass was present in this