Alka Seltzer Lab Report

Alka Seltzer Lab

That familiar fizzing you hear when you drop an Alka Seltzer tablet into a glass of water is the result of a chemical reaction, and chemical reactions are extremely prevalent when it comes to what living things do to carry out life processes. In addition, environmental conditions can alter the results of chemical reactions, and in this lab, we will be answering the

question: Will the temperature of the water affect the speed of the dissolving Alka Seltzers?

Hypothesis: The Alka Seltzer will dissolve fastest in hot water and slowest in cold water.

Materials: 3 400 ml glass beakers, 3 whole tablets of Alka Seltzer, thermometer, stopwatch/timer, thermal glove, hot plate, ice bath

Procedure:

Fill the 3 beakers with 250 ml of water from the sink.
Cool one beaker of water to 7℃. Use a thermometer to precisely measure.
Immediately place 1 whole tablet of Alka Seltzer into the beaker.
Use a stopwatch or timer to determine the amount of time it takes for the tablet to completely stop fizzing out or until it completely stops dissolving.
Record results in table.
Heat one of the other beakers of water

to 80℃. Use a thermometer to precisely measure. Caution: Be sure to use a thermal glove when handling hot objects!
Repeat steps 3-5.
Take the last beaker of water and measure the temperature to 18℃ (or about room temperature); adjust accordingly by heating or cooling the beaker of water to achieve exactly 18℃.
Repeat steps 3-5.
Compare your results.
Clean up: Dispose of the water in the beakers by dumping it into the sink. Caution: Be sure to use a thermal glove when handling hot objects!

Data:

TYPE AND TEMPERATURE OF WATER
ALKA SELTZER DISSOLVING TIME
Room temperature water (18℃)
48.72 sec
Cold water (7℃)
130.24 min
Hot water (80℃)
27.41 sec

Conclusion:

Analysis: By choosing water temperature as our environmental factor to test the Alka Seltzers in, we predicted that the tablet would dissolve fastest in hot water and slowest in cold water because we assumed that the higher the temperature, the faster the carbonated molecules would move in the Alka Seltzer, causing it to dissolve quicker. After conducting the experiment, we have concluded that this was just the case and our hypothesis was correct; our control group was dropping the tablet into room temperature water (18℃), and its dissolving time was 48.72 seconds. The beaker of cold water (7℃) caused the second Alka Seltzer to dissolve in a whopping 2 minutes and 10.24 seconds (or 130.24 seconds), while the last tablet dissolved in only 27.41 seconds in the hot 80℃ water, nearly 5x faster than it was in the cold water.
Alka Seltzer tablets are composed of sodium bicarbonate and citric acid and when they become dissolved in water, the sodium bicarbonate splits and forms sodium and bicarbonate ions; those familiar fizzing bubbles, or the carbon dioxide gas, produced in this reaction are caused by the bicarbonate ions coming into contact with hydrogen ions from the citric acid.

In order for the reaction to occur properly, the bicarbonate ions must react with the hydrogen ions in perfect synchrony. This is where the effect of water temperature comes in: the higher the temperature, the faster the molecules move, and the lower the temperature, the slower they move. (Higher water temperatures would increase the likelihood of the bicarbonate and the hydrogen ions coming into contact with each other in accordance, which would in turn cause the Alka Seltzer to dissolve

faster.)

Conclusion: One of the possible sources of error that could have occurred during the experiment is inaccurate measuring of the water in the beakers; if the three beakers of water contained even a little more or less water than the others, the results could become skewed because the amount of water can affect the time it takes for the tablets to dissolve. Another source of error lies in the obtainment of varying dissolving times for the Alka Seltzers--it is possible for a lab group to disagree upon what constitutes as “done dissolving/fizzing”. For example, in our group, the tablet in the cold 7℃ water took over 2 minutes, and at that point, some of us argued that it was still not done dissolving because we could see that there were still particles moving. Not only that, but