Gary Chiu Ms. Hunte
February 29, 2012
Lab Report: Mass Changes During Chemical Reactions
SNC2D2-02
Purpose:
To find out if mass is gained or lost during a chemical reaction.
Hypothesis:
The mass mass will will not change during a chemical reaction, and the mass mass of each each reaction will remain the same. According to the Law of Conservation of Mass, there will not be a change in the mass of the reactants when a reaction occurs. In addition, mass only changes when it is converted into energy, such as nuclear reactions.
Apparatus:
For a full, detailed detailed list of the apparatus, refer to Section 6.2 (Page 228-229 in Nelson Science Perspectives 10).
Method:
For a complete, step-by-step process on conducting the experiment, refer to Section 6.2 (Page 228-229 in Nelson Science Perspectives 10).
Observations: Reaction 1 Predicted mass change: Decrease, no change, or increase?
No change in the mass.
No change in the mass.
167.4g
201.9g
167.5g
201.5g
0.1g difference.
-0.4g difference.
There was little to no change in the mass, however, it increased.
The mass decreased.
Initial mass of reactants + container (g)
Final mass of products + container (g)
Change in mass (final – initial) (g)
Observed change in mass: Decrease, no change, or increase? Observed class results: Decrease, no change, or increase?
Reaction 2
Mean:
Median:
Mode:
Mean:
Median:
Mode:
0
0
0
-0.34
-0.45
-0.5
Lab Report: Mass Changes During Chemical Reactions
Conclusion:
In conclusion, the experiment was an absolute success and everything went to perfection. The purpose of the lab is to find out if the mass changes, and if so, how it changes. However, each reaction returned a different result. In the first reaction, there was no change in the mass, and was confirmed in the class results. The hypothesis was correct for reaction #1. In the second reaction, there was a decrease in the mass, and was confirmed by the class results. The hypothesis was incorrect for reaction #2. In the experiment, the antacid table dissolved with the water, released gas and created a chemical reaction. One can conclude that if the reactants undergo a physical change, the mass will not change and will remain the same. If the reactants undergo a chemical change, the mass can increase or decrease.
Discussion Questions: a)
The table in the “Observations” section records the
change in mass for each reaction.
Reaction #1 resulted in a 0 change in mass, while in Reaction #2, the mass decreased. b) The result from Part A is that there is no change in the mass. The results from other students’ are also a no-change in the mass. However, one group recorded a 0.1g
increase, and another group recorded a 0.1g decrease. All-in-all, the rest of the class recorded a 0g change. c) The average change in mass in the class for Part A is 0g. d) The result from Part B is that there is a decrease in the mass. The results from other students’ are also decreases in the mass. However, there were a few
outliers; one group
recorded a 0.7g increase and another group recorded a -0.9 decrease. The rest of the class recorded a -0.3 to -0.5 decrease. e) In Part A, there was no change. In Part B, there was a decrease in the mass. One reason for the different is that in Part B, a chemical reaction formed and gas was released from the reaction. The gas that was released may have escaped from the container, and may result in a lower mass measurement. In the first reaction, no gas was produced. f)
The average change in mass in the class for Part B is -0.34g.
Lab Report: Mass Changes During Chemical Reactions
g) Yes, the class results for Part B will differ if the reaction was carried out in a sealed
container. The gas that was formed in the reaction would not have left the container, and may condensate back into a liquid. If the gas did not escape, the reaction might r esult differently; with a mass increase or no change at all. h) It would be unsafe to conduct Part B in a sealed container because the gas that was formed may create tons of pressure in the container, and ultimately, the container may explode and seriously injure someone. i)
The total mass of the products of a c hemical reaction does not change from the total mass of the reactants. In Reaction #1, there was no change in the mass after the reaction, and before the reaction. The total mass of the products of a chemical reaction will be the same as the total mass of the reactants.
j)
The answer in question (i) is the same as the hypothesis. There are no differences.
