Transcript Lab Activity

Lab Activity
Acids and Bases
Scientific Title:
 The effect of various solutions on pH level.
Problem Statement:
 How can a pH indicator determine the pH
level of substances?
Hypothesis:
 If an indicator is used, then the acidity and alkalinity(base)
can be determined, because various colors will be observed
indicating the pH level of the substance due to the number of
hydrogen ions (H+).
Variables:
 Refer to the title, problem statement, and hypothesis to
identify the variables.
 Independent variable Dependent variable Constant/Control-
Materials:
 Cabbage juice
 13 test tubes
 1Test tube rack
 Variety of solutions (list all substances)
 Vinegar, baking soda, gingerale, antacid, orange juice, tap water,
pure water, salt water, windex, tea, ammonia, milk, liquid soap
 13 Pipettes
 Litmus paper (blue and red)
Procedures:
 1. Place the solutions in the test tubes.
 2. Add 3-4 drops of cabbage juice to each test tube.
 3. Observe and record observations on the data table.
 4. Use the litmus paper (red and blue) to determine whether
the substances are a base, an acid or neutral based on the
color of the paper.
 5.Record your observations.
Data Table:
 Copy the data table for a total of 13 solutions/substances.
 Complete column 1 by listing all of the 13 solutions in order as
listed under materials.
 Complete the second column by hypothesizing whether or not the
solution/substance is an acid, a base or is it neutral.
 Column #3, write the color observed and the pH level (the
number)
 Take a picture of the test tubes with the substances before and after
the indicator is added. Number the test tubes 1-6 and 7-12. Do not
include #13, which was the dish liquid in the cup. Include the
pictures after the 7 data questions and before the conclusion
paragraphs.
 #10 Tea
 #13 Dish liquid
Data Analysis:
 Please write the 7 analysis questions and leave space in between each for the answer(s).
 Answer to #6 (write the first bullet and choose one of the other 3 bullets to include as
part of the answer to #6.)
How does this relate to pH? The numbers on the pH scale run from 0 to 14
Substances with lower pH's have much much more hydrogen, or H+, than
substances with higher pH's. For example:
 Vinegar, with a pH of 3, has ten times more H+ than lemon juice, with a pH of
4.
 Lemon juice, with a pH of 4, has ten times more H+ than aspirin water, with a
pH of 5.
 Aspirin water, with a pH of 5, has ten times more H+ than milk, with a pH of
6.
Conclusion: Paragraph 1 -10 points
 The purpose of this lab was to determine how a pH indicator is
used to determine the pH level of various substances. The pH
indicator determines the acidity and alkalinity (base) of a
solution. If the pH level is less than seven,the substance is an
acid. If the pH is greater than seven, the substance is a base. If
the substance pH level is seven, it is considered neutral. The
procedures used was to first add the 13 substances to 13 test
tubes. The second step was the addition of the cabbage juice,
which was the indicator. The observations were then recorded
on the data table. Both the color observed and the pH level was
recorded. The independent variable is this activity was the
substances. The dependent variable was the pH level. The
constant was the cabbage juice.
Conclusion : Paragraph 2 – 20 points
 In this paragraph include your answers from the data analysis
questions. Include 1, 4 and 5; also what substances where
acidic and which were basic. Explain how you were able to
make that determination. Include the other 3 indicators that
are used to identify an acid or a base from your “Properties of
Acids and Bases” notes. Include the colors that are observed
from these indicators that will identify an acid from a base.
Conclusion: Paragraph 3- 15 points
 Include whether or not your hypothesis was supported and
explain. Also, what real-life or real-world applications are
related to the concepts of acids and bases.You can refer to
your 3 sets of notes for the answers, especially the notes on
“Writing and Naming Acids and Bases” from teacher web.
Include 4 applications. Two for acids and two for bases.