1
Table of Contents
Background Information ....................................................... 3
Purpose ...................................................................................... 5
Hypothesis ............................................................................... 5
Materials .................................................................................. 5
Procedure ................................................................................. 6
Data and Graphs ..................................................................... 9
Analysis ................................................................................... 19
Conclusion ............................................................................... 20
Bibliography ........................................................................... 21
Appendix ................................................................................. 22
2
Background Information
Beans originated in Mexico, Costa Rica, Guatemala and Honduras. But now beans
can be found all over the world, even in places that you would never think to find them.
And there are about 30 different kinds that are used as vegetables. In the United
States some of the most commonly grown kinds are garden peas, cowpea, lima beans,
snap beans, soybeans, lentils, kidney beans, pinto beans, chick-peas, and fava beans.
Beans extract some of the nitrogen in the atmosphere and are a good source of
protein when eaten. Many kinds of beans can be found in developed and undeveloped
countries. Beans contain proteins, carbohydrates and some essential vitamins and
minerals. The ancestors of snap beans originated between 6,000 and 8,000 years
before today. And some beans that are as old as 2,500 years old have been found
preserved in the Andes. As well as all the special kinds of beans grown today there
are common beans that didn’t have scientific names. Beans are either pole beans
(which means they are long and stringy and grow on a pole like a vine), and there are
bush beans (they grow short and thick like bushes). The leaves of pole beans tend to
be smaller than those of bush beans which tend to be larger. Some beans have
multiple leaves in a clump kind of like a clover and others have only one or two leaves in
a clump. The rate at which beans produce seeds depends on cultivar type and the size
of their leaves, which means that some beans will produce seeds in larger quantities
and faster than other kinds of beans.
pH is defined as “the negative logarithm of the effective hydrogen ion
concentration or hydrogen ion activity in gram equivalents per liter, used in expressing
both acidity and alkalinity on a scale whose numbers less than 7 indicate increasing
acidity, and numbers greater than 7 increasing alkalinity.” What this means is that pH
7 is neutral, solutions with pH numbers above that are basic (or alkaline), and solutions
with pH numbers below that are acidic. Numbers on the pH scale differ from each
3
other by a factor of 10 in how acid or basic they are (in other words, how many H+ or
OH- ions they have). This means that a solution with a pH of 5 has 10 times as many
hydrogen ions as one with a pH of 6, and a solution with a pH of 9 has 10 times as many
hydroxyl ions as one with a pH of 8.
However, when a chemical is added to water to change the pH of the solution, it is
not possible to add pure hydrogen ions or pure hydroxyl ions. The hydroxyl (OH-) ions
are bound to a cation to make a stable chemical. Perhaps the chemical used to change
the pH affects the bean growth as well as the pH. If so, the response of beans to
growing in different pHs would vary depending on what cation was used.
Different plants grow best in different pHs, but in general, most garden
vegetables prefer a slightly acidic soil, around pH 6.5. A pH below 6 or above 7 is
usually not as good for vegetable growth.
Pinto beans grow best in pH 6, and the higher pH the worse the pinto beans grow.
An experiment on the Internet tested how pinto beans grow in different pHs. The
person who did that project found that the pH does affect the growth of plants (in
this case beans) which was the opposite of his hypothesis.
Another person did an experiment on how mung beans grow in different pHs.
They found that they grew best in pH 6 and anything below or above that stunted the
beans’ growth, causing them to grow shorter.
4
Purpose
The purpose of this experiment was to test how beans grow in different pHs, and
see if the chemical used to change the pH affected the beans’ response to the
different pHs.
Hypothesis
The hypothesis used in this experiment was that the higher the pH, the poorer
the beans would grow, and that the beans would grow worst in the sodium (NaOH)
solution, best in the calcium (Ca(OH)2) solution, and that potassium (KOH) would be in
between.
Materials
The materials used in this project were:
1. One bag of mixed pinto and great northern beans from the grocery store
2. 26 4-quart plastic tubs
3. 78 ft. of 3/4” PVC pipe
4. 13 9” x 12” pieces of plastic needlepoint cloth
5. 14 one gallon jugs of distilled water
6. One plastic sprayer
7. One roll of paper towels
8. 500 gram jar of sodium hydroxide (NaOH) flakes
5
9. 500 gram jar of potassium hydroxide (KOH) flakes
10. 250 gram jar of calcium hydroxide (Ca(OH)2) powder
11. One roll of pH paper for pHs 5.5 - 8
12. One roll of pH paper for pHs 3 - 9
13. Disposable plastic gloves
14. One package of 3 oz. plastic cups
15. Hot glue gun
16. 10 sticks of hot glue
17. One 25 lb. bag of epoxy-coated aquarium gravel
18. Black marker
19. White labels
20. Ruler graduated in millimeters
21. Meter stick
22. Triple-beam balance scale
23. Scissors
24. Drill press with 1/2” bit
Procedure
1. Cut PVC pipe into 3” sections.
2. Cut needlepoint cloth pieces in half the short way:
3. Trim one piece of the needlepoint cloth so that it fits in the bottom of the vat.
Do this for each of 13 vats.
4. Mark the large (untrimmed) halves of the needlepoint cloth with 18 holes in a 6
x 3 grid about 2” apart.
6
5. Stack up the large (untrimmed) halves of the needlepoint cloth and drill 1/2”
holes in all the marked places with a drill press.
6. Glue 3” PVC tubes over the holes drilled in the needlepoint cloth.
7. Make 12 solutions, one gallon each: pH 7.5, pH 8, pH 8.5, and pH 9, for each of
the three chemicals (sodium hydroxide, calcium hydroxide, and potassium hydroxide).
The 13th solution (control) is plain distilled water. This is done in the garage so if the
chemicals spill, they don’t ruin the floor. This is done by adding small amounts of the
chemical powder/flakes to a gallon jug of distilled water, and repeatedly testing the
pH, until the proper pH is obtained. Remember to wear plastic gloves when handling
chemicals.
8. Label each vat with the chemical and pH, or water for the control.
9. Put the small pieces of needlepoint cloth into the bottoms of the vats (this
keeps the tubes from sealing to the bottoms of the vats, so the solutions can get in).
10. Fill the vat not quite full with the proper solution.
11. Place all of the pieces of needlepoint cloth with the tubes glued onto them
into the solutions with the tubes down in the solutions.
12. Soak about 200 beans of each type in plain water overnight.
13. Feed the epoxy-coated gravel down all of the holes until the tubes are full.
(This is so that the beans have something to grow into, and the epoxy coat on the
gravel keeps the gravel from reacting with the solution.) The tubes contain each
bean’s roots so the roots don’t get tangled, and the bean can be weighed at the end of
the experiment.
14. Fill the sprayer with distilled water.
15. Place the soaked beans on a wet paper towel, and spray them twice a day.
When some of them start to sprout, carefully place them over the gravel-filled tubes
and place tops over them (use the other 13 tubs for covers). Use 9 pintos and 9 great
northerns per vat.
16. Make a data sheet for each bean and assign it a bean number, for example,
Ca-7.5-P-1 means calcium pH 7.5 pinto7 bean #1.
17. Begin taking data on each bean when it is placed over a tube (height
measurements after they begin to grow).*
18. When the beans get too tall, remove the covers and keep spraying them until
their roots reach the solution. Any short beans are covered with the plastic cups
(personal greenhouses) at this point.
19. Take height measurements on the beans every day for 40 days.
20. Rotate the vats once each day in a caterpillar fashion. This is so that none of
the vats are closer to the window any more of the time than any of the others, so that
differences in light do not affect the results. Bean rotation is done in the following
manner:
window
6
5
4
3
2
1
7
8
9
10
11
12
13
a. Vat 13 is moved out of the way.
b. Vat 12 is moved into the 13 position.
c. Vat 11 is moved into the 12 position, etc. until position 1 is vacant.
d. Vat 13 is moved into position 1.
21. After 40 days, pull out the beans and weigh them on the triple beam balance.
* All the beans were starting to sprout when they were placed over the holes. If a bean died before it
put down roots, it was listed in the Appendix as never sprouted and not used in the analysis.
8
Data
The data presented here are the averages for all beans in a vat. The individual
measurements for each bean are in the Appendix.
Day
Ca 9
Ca 8.5
ca 8
Ca 7.5
Water
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
0
0
0
0
0
0
0
0
2
8
13
20
43
66
98
128
150
168
178
192
205
219
227
269
282
293
299
307
316
319
325
328
330
332
337
340
343
348
355
359
0
0
0
0
0
0
0
2
10
16
28
42
69
96
125
150
178
204
226
247
260
277
288
296
308
321
326
322
334
352
356
359
363
367
370
372
374
377
385
393
0
0
0
0
0
0
0
0
0
1
9
19
51
68
110
145
179
204
224
244
267
297
319
328
342
358
364
373
386
393
399
405
411
413
417
418
422
426
435
440
0
0
0
0
0
0
0
2
5
22
46
78
114
134
160
191
214
235
253
274
292
306
320
335
345
354
356
359
367
370
374
378
384
386
390
393
396
400
403
410
0
0
0
0
0
0
1
2
3
9
20
55
93
115
148
181
209
231
250
273
287
305
307
321
328
339
340
344
351
354
358
362
367
368
365
366
367
368
372
377
Weight (g)
1.44
1.53
1.89
1.87
1.81
9
450
Water
400
Ca 7.5
350
Ca 8
Ca 8.5
300
Height mm
Ca 9
250
200
150
100
50
0
2
Water
1.8
Ca 7.5
1.6
Ca 8
Weight grams
1.4
Ca 8.5
1.2
Ca 9
1
0.8
0.6
0.4
0.2
0
10
11
0
50
100
150
200
250
300
350
400
450
7.5
8
Growth Curves for Calcium
ter
Wa
Ca
ca
Ca
8.5
Ca
9
200
150
100
50
0
450
400
350
300
250
Day
K9
K 8.5
K8
K 7.5
Water
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
0
0
0
0
0
0
1
6
14
18
25
35
69
93
127
162
181
200
212
231
246
259
270
281
292
305
313
319
329
332
342
345
367
373
380
382
386
386
395
403
0
0
0
0
0
0
3
6
6
12
23
42
81
110
140
167
187
208
229
246
264
288
312
343
353
368
370
375
365
378
391
396
398
401
408
412
416
422
430
437
0
0
0
0
0
0
8
20
33
39
47
81
112
135
158
192
212
229
246
255
265
272
286
294
313
324
335
342
356
360
368
372
379
381
388
390
395
406
413
421
0
0
0
0
0
0
0
5
7
19
33
72
119
150
177
200
219
239
261
282
292
302
309
319
324
339
340
347
355
361
367
367
370
373
377
379
384
390
394
400
0
0
0
0
0
0
1
2
3
9
20
55
93
115
148
181
209
231
250
273
287
305
307
321
328
339
340
344
351
354
358
362
367
368
365
366
367
368
372
377
Weight (g)
1.81
2.23
1.59
1.92
1.81
12
450
Water
400
K 7.5
350
K8
K 8.5
300
K9
Height mm
250
200
150
100
50
0
2.5
Water
K 7.5
2
K8
Weight grams
K 8.5
K9
1.5
1
0.5
0
13
14
200
150
100
50
0
450
400
350
300
250
Potassium Growth Curves
ter
Wa
K7
.5
K8
K 8
.5
K 9
150
100
50
0
450
400
350
300
250
200
Day
Na 9
Na 8.5
Na 8
Na 7.5
Water
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
0
0
0
0
0
0
0
0
2
7
38
72
106
126
156
189
211
221
232
247
253
266
275
287
all dead
0
0
0
0
0
0
7
16
26
31
34
43
75
93
115
141
159
176
183
194
202
215
223
227
232
238
241
242
247
252
256
257
259
259
274
274
276
280
287
294
0
0
0
0
0
0
1
8
19
27
44
66
101
122
147
176
191
205
219
231
242
252
265
277
286
295
298
302
309
313
317
321
327
328
334
335
336
338
341
346
0
0
0
0
0
0
1
6
10
13
18
31
55
80
117
161
194
220
241
270
293
311
327
343
346
355
360
369
374
380
385
388
409
400
405
406
408
412
415
421
0
0
0
0
0
0
1
2
3
9
20
55
93
115
148
181
209
231
250
273
287
305
307
321
328
339
340
344
351
354
358
362
367
368
365
366
367
368
372
377
Weight (g)
1.33
1.43
1.49
1.75
1.81
15
450
Water
Na 7.5
400
Na 8
350
Na 8.5
300
Na 9
Height mm
250
200
150
100
50
0
2
Water
Weight grams
1.8
Na 7.5
1.6
Na 8
1.4
Na 8.5
1.2
Na 9
1
0.8
0.6
0.4
0.2
0
16
17
0
50
100
150
200
300
250
350
400
450
7.5
8
Sodium Growth Curves
ter
Wa
Na
Na
Na
8.5
Na
9
0
50
200
150
100
450
400
350
300
250
450
450
400
400
350
350
300
300
250
200
250
150
200
100
150
50
100
0
50
0
Na
7.5
8
Ca
8.5
9
K
W
ate
r
Overall Comparison of Heights
2.5
2.5
2
2
1.5
1.5
1
1
0.5
0.5
0
0
Na
pH
pH
Ca
pH
pH
K
7.5
8
8.5
9
W
ate
r
Overall Comparison of Weights
18
Analysis
In calcium the great northerns grew a little bit better than the pintos. But in
potassium and sodium the pintos grew a little bit better than the great northerns.
These graphs are shown in the Appendix along with the raw data. But for the most
part the growth curves were pretty much the same shapes for both kinds of beans in
a vat. Because of this, the average of all of the beans in a vat was used for the final
graphs.
For calcium pH 8 was the pH that the beans grew best in and they grew worst in
pH 9, for both height and weight. They grew better in pH 7.5 than they did in plain
distilled water, better in pH 8 than in pH 7.5, but then worse at pH 8.5 and worst at
pH 9. From this it is concluded that the best pH for the beans for calcium was 8.
In potassium the beans grew best in pH 8.5 for both height and weight. For
height they did better in pH 7.5 than in water, better in pH 8 than pH 7.5, and better
yet in pH 8.5 than in pH 8, and worse in pH 9. For weight they followed the same
trend except that the pH 8 weights were strangely low. This was probably just a
fluke, because the beans varied a lot in how robust or skinny they were, and there
seemed to just have been a lot of tall, skinny beans in that vat by chance. The
conclusion here is that pH 8.5 is best for beans growing in a potassium solution.
In sodium the beans grew best in 7.5 and worst in 9 for the height, and for the
weight. After pH 7.5 they did worse on both height and weight the higher the pH
went. In fact it is worse than it looks on the graphs because by day 24 all the beans in
sodium 9 died. They had seemed to be growing fine, but then within about 3 days they
all bent over and went limp. The beans appeared to have been poisoned by the sodium,
although it took a while, as if they could handle just so much sodium, and then they
couldn’t take it any more. This could account for why the beans did worse in the more
concentrated solutions, because there was more sodium in them as well as a higher pH.
19
Except for an occasional bean here and there, the sodium 9 vat was the only one
where the beans all died. All the other vats of beans made it the 40 days and still
looked good.
The heaviest and tallest beans on average were in the potassium solutions.
Potassium is an ingredient in Miracle-Gro plant fertilizer, presumably because it is
good for plants. Calcium and sodium are not ingredients in Miracle-Gro, so they must
either be neutral for plants or bad for them. In fact this experiment found that
sodium seems to poison beans. Since potassium is a plant nutrient, this is probably
why the tallest and heaviest beans were in potassium. In fact the potassium 8.5 vat
had an average bean weight of 2.23 g which was the only one that was over 2 grams.
The experimenter learned that the chemical used to change the pH of a solution
does have an effect on the growth of the beans, as well as the pH that is in the water.
The hypothesis was partially correct. The sodium solutions did turn out to be the
worst for the beans. But the calcium solution did not turn out to be the best. The
best one was the potassium. And there was a difference in how the beans responded
to different pHs depending on what chemical was used.
Conclusion
This experiment tried to find out how the beans responded to the different
pHs and whether there was a difference between how they responded depending on
which chemical was used to change the pH. In calcium and potassium, the beans grew
best in the middle range pHs (8 to 8.5) and worst in the high pH of 9. For sodium,
they grew best in the lowest pH, 7.5, and steadily worse as the pH got higher. In pH
9 the beans grew so poorly that within a few days during the third week they all died
and did not even make it to the end of the experiment.
Therefore, the conclusion is that it does matter what chemical is used to
change the pH of the water, because it will affect the results obtained when growing
beans.
20
Bibliography
Cheng, G., Cheung, W., Wong, L., and Yen, C., date unknown. The Effects of pH on
Mung Beans. http://members.aol.com/ScienzFair/phmung.htm
Conway, K., Lucarelli, A., O’Connor, J., and Rodgers, J., 1998. The Effect of Different
Types of Water on the Growth of Bean Plants. http://jrscience.wcp.muohio.edu/
nsfall98/FinalArticles/Final.TheEffectofDifferen.html
Fageria, N. and Biligar, V., 1998. Growth and Nutrient Uptake by Common Bean, Lowland Rice, Corn, Soybean, and Wheat at Different Soil pH and Base Saturation on an
Inceptisol. http://www.nal.usda.gov/ttic/tektran/data/000007/27/
0000072730.html
Mississippi State University, 2002. Vegetables: the Ideal Soil pH. http://
muscares.com/lawn/garden/vegetables/soil/ph.html
Nguyen, M., 2002. Sinking pH. http://www.usc.edu/CSSF/Current/Projects/
J1622.pdf
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