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

1 2 3 4 Standard Dev.

Mean

Stirring (s)

47.5

45.3

41.7

40.5

3.23

43.8

Shaking (s)

48.3

40.8

44.7

47.3

3.35

45.4

Normal(s)

52.55

53.89

46.14

51.74

2.95

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 1 2 3 4 100 mL 47.8

48.8

48 49.5

48.525

0.780491

150mL 47.7

49.3

49 44.2

47.55

2.338803

*All data measured in seconds unless noted 200mL 47 43 49.4

45.2

46.15

2.714774

*All data should be rounded to 3 significant figures *Numbers like 47 and 48 are actually 47.0 and 48.0

100 mL 150 mL 200 mL *Avgs~ 48.5

47.6

46.2

50 45 40 35 30 25 20 15 10 5 0

Graphical Analysis

Reaction Time vs. Amount of Water

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) 50.3

52.4

50.1

54.2

51.7

Mean: 51.7

Standard Deviation: 1.67

Tablet Then Water (s) 48.7

50.3

49.1

51.7

47 Mean: 49.4

Standard Deviation: 1.76

52 51,5 51 50,5 50 49,5 49 48,5 48

Graphical Analysis

Order or Operations

Water Then Tablet 1 Tablet Then Water 2

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

Water Time to Dissolve (S) Mean Standard Deviation

52.55

53.89

46.14

51.74

52.55

53.89

Coca-Cola Diet Pepsi Caffeine Free

56.17

56.62

57.61

56.49

57.07

Fruit Punch

97.88

98.7

86.94

56.4

0.225

57.1

0.457

94.5

5.36

100 90 80 70 20 10 0 60 50 40 30

Graphical Analysis

Название диаграммы

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: Water Temperature of the 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

Hot Water Temp. (degrees Celsius)

29.5

Time for reaction to stop (s) (Trial 1) Trial 2 (s)

28.8

25.3

Trial 3 (s) Water in beaker (mL)

29.1

150

Avg. time (s) Standard Deviation

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 Time to dissolve (s)

100 80 60 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

Time to Dissolve(s)

Average Standard Deviation

Halves

45.17

50.7

59.9

49.74

49.58

45.68

50.13

5.303517

Sixths

49.39

50.63

52.12

54.65

42.88

49.82

49.92

3.938765

Crushed

20.15

14.03

17.96

18.67

18.81

21.85

18.58

2.6193772

Graphical Analysis

60,00 50,00 40,00 30,00 20,00 10,00 0,00

Effect of Tablet Size on Disolving Time 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