Chemistry 173 6/7 B
Phenomenon

Alka-Seltzer Dissolving in water

Water causes the citric acid and sodium
bicarbonate to react, releasing carbon
dioxide which disperses the aspirin
throughout the water

Measured: Dissolution Time

Definition of Dissolved: The tablet is no
longer visible
Experiment One
Manipulated Variable: Shaking or Stirring
the Solution
Hypothesis: If shaken/stirred, the time will
decrease substantially.
Data
Trials
Stirring (s)
Shaking (s)
Normal(s)
1
47.5
48.3
52.55
2
45.3
40.8
53.89
3
41.7
44.7
46.14
4
40.5
47.3
51.74
Standard Dev.
3.23
3.35
2.95
Mean
43.8
45.4
51.1
Graphical Analysis: Stirring
Graphical Analysis: Shaking
Discussion
• The data supports the initial hypothesis
overall because according to the data table
the time decreases substantially compared
to the initial test
• Difficulties: human and physical error
• For a future experiment, we would try to be
more accurate as far as timing and
measurement
Experiment Two
Manipulated Variable: Amount of Water
Hypothesis: If we add water to the beaker,
then the reaction time of the alka-seltzer
½ tablet and water will not change.
Data
Trial
Avg
St. Dev
100 mL
150mL
200mL
1
47.8
47.7
47
2
48.8
49.3
43
3
48
49
49.4
4
49.5
44.2
45.2
48.525
47.55
46.15
0.780491
2.338803
2.714774
*All data measured in seconds unless noted
*All data should be rounded to 3 significant figures
*Numbers like 47 and 48 are actually 47.0 and 48.0
100 mL
*Avgs~
150 mL
48.5
200 mL
47.6
46.2
Graphical Analysis
Reaction Time vs. Amount of Water
50
45
40
Reaction Time (in s)
35
30
25
20
15
10
5
0
100 mL
150 mL
Amount of Water (in mL)
200 mL
Discussion

Hypothesis
 Supported (for the most part)
 Change in reaction time insignificant (basically +/- 1 sec.
per 50 mL)

Difficulties





½ tablet hard to get exact
Didn’t clean out beaker perfectly-not perfect tap water
Manual timing
Exact water amount
Things to change
 Use full tablet to eliminate ½ tablet problems
 More exact timer
 More time to work on lab-more trials, cleaner beaker,
better data, etc.
Experiment Three
Manipulated Variable:Water or Tablet first?
Hypothesis: The order of operations for
dissolving alka-seltzer tablets will NOT
affect the time it takes to dissolve the
tablet.
Data
Water Then Tablet (s)
Tablet Then Water (s)
50.3
48.7
52.4
50.3
50.1
49.1
54.2
51.7
51.7
47
Mean: 51.7
Mean: 49.4
Standard Deviation: 1.67
Standard Deviation: 1.76
Graphical Analysis
Order or Operations
52
51.5
Time to Dissolve (s)
51
50.5
50
49.5
49
48.5
Water Then Tablet
Tablet Then Water
1
2
48
Discussion

Our findings for the order or operations experiment is that it doesn't
matter if you put the water or Alka-Seltzer in first. This is because
the standard deviation we calculated was 2 seconds and the
difference between our two means is 2 seconds.

Our initial hypothesis was that the order wouldn't make a difference
in the time it takes to dissolve the tablet, and we were happy to see
that this was true supported by our data.

The only difficulty we encountered when conducting our experiment
was that the tablet would partially dissolve in the beaker that was
supposed to be dry (for the tablet then water portion) because there
was leftover water in it from using it in the other portion of our trials.

We fixed this by simply drying out the beaker with a paper towel.
There are no things that we would change for a future experiment.
Experiment Four
Manipulated Variable: Type of Liquid
Hypothesis: Because the alka-seltzer table
was designed for water, it will dissolve
faster in water than in any other liquid.
Data
Time to
Dissolve
(S)
Water
Coca-Cola
Diet Pepsi
Caffeine Free
52.55
56.17
57.61
97.88
53.89
56.62
56.49
98.7
57.07
86.94
46.14
Fruit Punch
51.74
Mean
Standard
Deviation
52.55
56.4
57.1
94.5
53.89
0.225
0.457
5.36
Graphical Analysis
Chart Title
100
90
Time Dissolved(In Seconds)
80
70
60
50
40
30
20
10
0
Water
Coca-Cola
Diet Pepsi Caffeine Free
Fruit Punch
Discussion

Supported hypothesis

Problems:
 Inexact tablet sizes
 Hard to see tablet
 Hard to determine when dissolved

Next time:
 Use whole tablets
 Get a light to illuminate tablet
 Conduct more trials
Experiment Five
Manipulated Variable: Temperature of the
Water
Hypothesis: Our hypothesis was that the
water at 29.5 degrees Celsius would
dissolve the Alka-Seltzer tablet faster than
the water at 19.5 degrees Celsius (normal
temperature of tap water), which would
dissolve the tablet faster than the water at
9.5 degrees.
Data
Temp.
(degrees
Celsius)
Time for
reaction
to stop (s)
(Trial 1)
Trial 2 (s)
Trial 3 (s)
Water in
beaker
(mL)
Avg. time
(s)
Standard
Deviation
Hot Water
29.5
28.8
25.3
29.1
150
27.7
2.11
Tap Water
19.5
51.0
53.4
48.6
150
51.0
2.4
Cold
Water
9.5
82.9
86.1
81.7
150
83.6
2.27
Graphical Analysis
The effect of water temperature on
the solubility of Alka-Seltzer tablets
100
80
Time to dissolve 60
(s)
40
20
0
0
10
20
30
Temperature of water (degrees Celcius)
40
Discussion

Our data does support our initial hypothesis. Just as
we predicted, the tablet dissolved significantly faster
with warmer water.

Some difficulties we encountered in our experiment
included getting the water to exactly the right
temperature, determining when the tablet was
completely dissolved, and stopping the timer at the
precise moment.

In future experiments, I would perhaps change the
temperatures used in the experiment or the size of
the Alka-Seltzer tablets (use whole tablets instead of
half).
Experiment Six
Manipulated Variable: Size of Tablet
Hypothesis:
Data
Halves
Sixths
Crushed
45.17
49.39
20.15
50.7
50.63
14.03
59.9
52.12
17.96
49.74
54.65
18.67
49.58
42.88
18.81
45.68
49.82
21.85
Average
50.13
49.92
18.58
Standard Deviation
5.303517
3.938765
2.6193772
Time to Dissolve(s)
Graphical Analysis
Effect of Tablet Size on Disolving Time
60.00
Time to Disolve(s)
50.00
40.00
30.00
20.00
10.00
0.00
Amount of Tablet
Discussion

Compared to a half tablet, dividing the
tablet into sixths does not seem to make
much of a difference. The averages are
close, and the standard deviation allows
for overlap. Therefore, it would not be
practical for a consumer to divide the
tablet into sixths. However, crushing the
tablet does seem to result in a reduction
in dissolving time.
Overall Conclusion

What should remain the same
 Pour a normal sized glass of water, then put in
tablet
 Water is best
 Amount of water, order don’t matter
 Traditional is more convenient

What could be changed
 Use warm water
 Should stir water
 Consumer could crush tablet first