BIOL 103 Walden Testing the Impact of Different pH Levels on Plant Growth Questions

Data Sheet: Activity – Acids and Bases
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Name
Course
Date
Leabra Boyd
BIOL 103
1/12/23
Activity Data Code:
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1
Procedure I – pH of Household Solutions
Complete the table below using your data from Procedure I. Based on the measured pH
determine whether each solution is acidic, basic, or neutral.
Data Table I
Solution Number
Solution
Solution pH
Acidic, Basic, or
Neutral?
1
Battery Acid
0.00
Acidic
2
Lemon Juice
2.00
Acidic
3
Red Wine
3.80
Acidic
4
Water
7.00
Neutral
5
Antacid
10.00
Basic
6
Ammonia
12.00
Basic
7
Oven Cleaner
14.00
Basic
Observations and Questions
[1] Which household solution in Data Table I is the most basic? What information helped you
to come to that decision? What can you explain about the chemical composition of the solution
based on its pH (i.e. what does this tell us about the concentration of H+ ions in this solution)?
Answer: The most basic substance that is shown in the data table after reviewing the Solution
pH readings is that of the oven cleaner. Basics are those substances that have a pH reading
of greater than 7. The oven cleaner has the highest reading over that baseline with a pH of 14.
The pH of a solution is a measure of the concentration levels of hydrogen ions in the solution.
A solution that has a high number of hydroxide ions is basic and has a high pH value.
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Procedure II – pH of Biological Solutions
Complete the table below using your data from Procedure II. Based on the measured pH
determine whether each solution is acidic, basic or neutral.
Data Table II
Solution Number
Solution
Solution pH
Acid or Base?
1
Urine
5.25
Acidic
2
Liver Bile
8.60
Basic
3
Skim Milk
6.60
Acidic
4
Tear Fluid
7.00
Neutral
5
Seawater
8.00
Basic
6
Blood Plasma
7.40
Basic
7
Stomach Acid
2.50
Acidic
Observations and Questions
[2] Which biological solution in Data Table II is the most acidic? What information helped you
to come to that decision? What can you explain about the chemical composition of the solution
based on its pH (i.e. what does this tell us about the concentration of H+ ions in this solution)?
Answer: Of these solutions Stomach Acid is the most acidic with a pH of 2.50. With neutral
being a reading of 7.0 on the pH scale those solutions that are further away from neutral would
be the most acidic. A solution with a high number of hydrogen ions is acidic and will have a
lower pH value on the scale.
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Procedure III – Adding Acid Solution to the Buffer Solution
Complete the table below using your data from Procedure III.
Data Table III
Number of Added
Drops
pH of Non-Buffer Solution
(Water)
pH of Buffer Solution
0
7.00
7.00
1
2.52
6.99
2
2.22
6.97
3
2.05
6.96
4
1.92
6.94
5
1.82
6.93
Observations and Questions
[3] What happens to the pH of the water as you add drops of the acid solution (Data Table III)?
What is the chemical basis of this change in the pH of the water as acid is added (i.e. what is
happening to the H+ ion concentration)?
Answer: As acid is added to the water the pH levels of the water decreases, meaning that it
becomes more acidic. As the solution becomes more acidic this means that the number of
hydrogen ions that are present in the solution are increasing.
[4] Calculate the percent change of pH for water using the formula below. Show your work for
maximum points.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
Answer: Percent Change of pH = 100% x (1.82 – 7.00) / 7.00
Percent Change of pH = 100% x (-5.18) / 7.00
Percent Change of pH = 74%
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[5] Calculate the percent change of pH for the buffer using the formula below. Show your
calculations for maximum points.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
Answer: Percent of Change of pH = 100% x (6.93-7.00) / 7.00
Percent of Change of pH = 100% x (-0.07) / 7.00
Percent of Change of pH = 1%
[6] What happens to the pH of the buffer as you add drops of acid? How do the changes seen
in the buffer solution compare to those seen in the water solution? Be specific.
Answer: A buffer solution is more resistant to change in pH when small amounts of acid or
base are added to them. Upon review of the data table, it can be seen that the initial pH of the
buffer solution is 7.00 (neutral), but when drops of acid are added, there is a slight change in
pH noted. This is different than what occurs when the acid drops are added to the water
where there is a more substantial change, and the water becomes more acidic in nature.
Buffer solutions are used so that pH remains more constant and can resist changes in pH
more effectively.
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Procedure IV – Adding Base Solution to the Buffer Solution
Complete the table below using your data from Procedure IV.
Data Table IV
Number of Added
Drops
pH of Non-Buffer Solution
(Water)
pH of Buffer Solution
0
7.00
7.00
1
11.48
7.01
2
11.78
7.03
3
11.95
7.04
4
12.08
7.06
5
12.18
7.07
Observations and Questions
[7] What happens to the pH of the water as you add drops of the base solution (Data Table
IV)? What is the chemical basis of this change in the pH of the water as base is added (i.e.
what is happening to the H+ ion concentration)?
Answer: Upon review of the data collected, one can see that as the buffer solution is added to
the water the pH level recorded is higher, taking the water from a neutral to more basic in
nature. The pH of a solution is a measure of the concentration levels of hydrogen ions in the
solution. A solution that has a high number of hydroxide ions is basic and has a high pH value.
[8] Calculate the percent change of pH for water using the formula below. Show work for
maximum points.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
Answer: Percent Change of pH = 100% x (12.18 – 7.00) / 7.00
Percent Change of pH = 100% (5.18) / 7.00
Percent Change of pH = 74%
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[9] Calculate the percent change of pH for the buffer using the formula below. Show work for
maximum points.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
Answer: Percent Change of pH = 100% x (7.07 – 7.00) / 7.00
Percent Change of pH = 100% x .07 / 7.00
Percent Change of pH = 1%
[10] The buffer solution is said to “resist” a change in pH. Compare the percentage changes for
the water solution and the buffer solution. Do these percentages support a resistance to
change for the buffer solution? Explain your answer.
Answer: Upon review of the data recorded in the table, these percentages do support that a
buffer solution is “resistant” to change. The changes that occurred when adding the acid to the
buffering solution were minimal and thus prove the point that buffering solutions are able to
resist changes in pH levels even when acidic substances are introduced. The change in the
buffered solution with the addition of 1 – 5 drops only changed 0.07 in total in pH levels.
[11] In your own words and with proper terminology, explain the chemical basis of how the
buffer resists pH changes when the base is added. (HINT: Answers should describe how
buffers prevent the base from binding with free-floating H+ ions.)
Answer: The stronger acid which is introduced to the buffer reacts with the weak acid that is
contained in the buffered solution and thus forms a weak base which will produce a few H+ H+
ions within the solution thus impacting the change in pH levels minimally. Buffers work by
neutralizing acid (H+ ions) or base (OH- ions) to maintain a moderate pH level, making them
either a weaker acid or base solution.
[12] Design an experiment testing the impact of different pH levels on plant growth.
a) Background Information and Question of Interest: Start by giving some background
information, specifically describing what scientific observations or evidence led you to
want to conduct your experiment. Next, state the question you are interested in
answering through your experiment design. Be as specific as possible.
Answer:
b) State your hypothesis. Include what you are comparing (experimental vs control groups)
and what you will measure. As a reminder, your hypothesis should be written as a
statement, not a question.
Answer:
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c) Describe your experimental design. How will you conduct your experiment? How will
you introduce replication? What factors will you keep constant (i.e. control variables)?
Answer:
d) State your groups and variables. Be specific.
•
•
•
•
•
Independent Variable:
Dependent Variable:
Control Variables:
Experimental Group:
Control Group:
e) Provide pretend results.
Answer:
f) State your conclusion. Your conclusion should specifically state whether or not your
hypothesis is supported by the pretend results.
Answer:
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