Name _______________________________
CT-
/25
/10
Date: ________________________________
Investigating Acids and Bases
Purpose
To determine how indicators can be used to identify common substances as either acidic
or basic.
Hypothesis (Use your textbook – pg. 160-163)
Which substances are acidic? Which substances are basic? Which substances are neutral?
(T - 3)
Materials
1 spot plate
litmus paper (red and blue)
phenolphthalein indicator
bromothymol blue indicator
hydrochloric acid
sodium hydroxide
distilled water
vinegar
Borax
KOH
vegetable oil
baking soda
Windex
citric acid
Procedure
1. Using masking tape label the first row of wells #1 (for red and blue litmus paper); the
second row #2 (for phenolphthalein indicator); and the third row #3 (for bromothymol
blue indicator).
2. Place approximately three drops of solution #1 into the first row.
3. Place a small piece of red litmus paper and blue litmus paper in the first well; a drop
of phenolphthalein in the second row, and bromothymol blue in the third.
4. Wait a few seconds and record the colour change in the observation table.
5. Repeat steps 2, 3, 4 and 5 for the rest of the solutions.
6. Clean the spot plate.
Note: You will have to clean the tray during the experiment due to lack of a
sufficient amount of wells.
Investigating Acids and Bases
Observations: (C-25)
Substance
1.
hydrochloric
acid
2.
sodium
hydroxide
3.
distilled water
4.
vinegar
5.
Borax
6.
KOH
7.
vegetable oil
8.
baking soda
9.
Windex
Indicator #1
Red Litmus
Paper
colour
Indicator #2
Blue Litmus
Paper
colour
Indicator #3
Phenolphthalein
Indicator
colour
Indicator #4
Bromothymol
Blue
colour
Is the solution
an Acid, a
Base or
Neutral?
10. citric acid
Analysis: Answer the following in the space provided.
1. Give two characteristics of an acid and two characteristics of a base. (2 – T)
2. What is an indicator? (1 – T)
3. How are Bromothymol blue and phenolphthalein used as indicators? What colours do
they turn and when? (4 – T)