DESIGNING A PRACTICAL WORK
RQ: How does the addition of Alka Seltzer affect the pH and temperature of an acidic solution?
Introduction: Alka Seltzers are tablets that are used to neutralize an acid stomach. In this
experiment, you will be testing the effects that Alka Seltzers has on coca cola, which is representing the
acid stomach. You will test to see if the effects differ between using a whole tablet and a crushed tablet.
Prediction: I predict that the effects will not differ when you are using a whole tablet compared
to a crushed tablet in the pH and temperature of cola. I predict the pH of the solution will decrease as
the purpose of the tablet is to neutralize. I predict that the temperature will not be affected, therefore
staying the same.
The independent variable in this experiment is the crushed and the whole tablet. The dependent
variable in this experiment is pH and the temperature of the cola. The factors to be controlled are the
start temperature and pH of the cola. My hypothesis is that if I put a whole and a crushed Alka Seltzer
tablet into two different beakers of cola, then the outcome will be that the pH will increase, the
temperature will not be affected and there won’t be any changes if the two solutions were compared.
Materials:
-
pH sensor
Temperature sensor
Coca Cola
Two Alka Seltzer tablet
Spoon or knife
Two 100mL beakers
Method:
1. Start the experiment by pouring 60mL of coca cola into two different 100mL beakers.
2. Test the temperature and the pH and make sure they are equal to each other, so that the pH
and temperature will not affect the outcome.
3. Drop 1 whole Alka Seltzer tablet into the first beaker and label it solution A.
4. Crush 1 whole Alka Seltzer tablet with a knife or spoon on a clean surface, and pour into the
other beaker, labeling this solution B.
5. Leave for 1 minute.
6. Test the pH and temperature of both, washing both sensors in between using them, and take
down the results.
7. Compare the results, noting the initial temperature and pH compared to the final temperature
and pH.
8. Now compare the two final solutions to each other, and note down if there are any differences
between solution A and solution B.
SAFETY INSTRUCTIONS:
-
Be aware that the experiment could be altered if the pH sensors are not cleaned between using
them and this will affect your final outcome.
Do not test the Alka Seltzer by adding it into water and drinking it, unless in your stomach really
is upset. Any medicine should not be taken, unless necessary.
DATA RESULTS:
Initial temperature
Initial pH
New temperature
New pH
Solution 1 (Whole Tablet)
30.4
2.27
28.9
6.09
31
7
30.5
6
30
Solution 2 (Crushed Tablet)
30.6
2.18
29.3
6.23
5
29.5
29
28.5
Coke w. Whole
tablet
4
Coke w. Whole
Tablet
Coke w. cruhed
tablet
3
Coke w.
Crushed Tablet
2
28
1
0
Initial pH
New pH
Evaluation:
The pH was the most obvious changing subject in this experiment, as it dropped quickly first in
the graph, and ended up slowing down at the end once it reached above 6 on the pH scale. This
relationship shows that the Alka Seltzer, when added in water, would not do any major changes to the
water, however actually doing a test with water would show if there are any major changes, however
the ingredients are now added to the water, meaning that once it reaches your stomach the ingredients
will still work to put an end to a acid stomach, and make it less acid. There were no major changes in the
temperature, however small changes such as a 1 degree change which should still be noted.
Conclusion:
In the conclusion to the experiment of what the effects from an Alka Seltzer, being crushed or
whole and dropped in to a coke, would be I found that the Alka Seltzer generally turned the acidic coke
back to near water pH, which means more neutral pH. My hypothesis was partly proved, meaning that
the pH would increase once added to the cola. My hypothesis was also a little untrue, meaning that I
believed originally that there would be no temperature and no changes between the two solutions,
however there were small, but notable, changes between the two solutions. I think maybe this is
because the crushed Alka Seltzers was stronger as it diffused into the cola with a stronger power, also
fizzing up the cola a lot more than the whole tablet did. This was something that I noticed, however it
was not part of my original theory. So in the end, I learned that Alka Seltzer, if used as a whole tablet,
will work fast. If used crushed it will fizz up the water, and act a little faster when taken with water to
settle an acid stomach.