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IDENTIFYING PH USING NATURAL
SOURCES AS INDICATORS
La’Darion RobertsPeriod 3LaSalle
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PURPOSE The Purpose of this lab is to measure
the pH of Various household items using a natural indicator prepared from Cabbage Leaves. This demonstration will help with understanding the readings of a pH scale, and how to use indicators to determine the pH of a substance.
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WHAT YOU WILL NEED… • knife • red cabbage leaves • 1-cup measure • hot water • 2 jars • clean white cloth • teaspoon • tape • 3 sheets of plain white paper • pencil • ruler • 10 clear plastic cups • white vinegar (CH3COOH) • baking soda (NaHCO3) • household ammonia • dropper • various household items
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PROCEDURES Put ½ cup of finely
chopped red cabbage leaves in a jar and add ½ cup of hot water. Stir and crush the leaves with a spoon. Continue the extraction until the water is distinctly colored.
Strain the extract through a piece of cloth into a clean jar. This liquid is your natural indicator.
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PROCEDURE Tape three sheets of
paper end to end. Draw a line along the center and label it at 5 cm intervals with the numbers 1 to 14. This is your pH scale.
Pour your indicator to about 1 cm depth into each of three plastic cups. To one cup, add several drops of vinegar
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PROCEDURE to the second add a
pinch of baking soda, and to the third add
several drops of ammonia.
***The resulting colors indicate pH values of about 3, 9, and 11, respectively. Place these colored positions on your pH scale.
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PROCEDURE Repeat Step 4 for
household items: Lemon Juice, 2% Milk, Coffee, Mouthwash, Toothpaste, distilled water, laundry detergent(powder), dish washing soap
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ANALYSIS AND CONCLUDE What was the
color of the indicator at acidic, neutral, and basic conditions?
The color of the indicator changed to a light pink/red and color when an acidic substance was added, it remained the same/turned lighter for the neutral(distilled water) and turned a deep green/blue for the basic. These colors closely resembled the colors on the pH scale.
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ANALYSIS AND CONCLUDE What chemical
changes were responsible for the color changes?
The color changes occurred because each substance had a different concentration of [H+] and [OH-] ions, therefore causing the pH to be higher(basic) or Lower(acidic)
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ANALYSIS AND CONCLUDE Label the
materials you tested as acidic, basic, or neutral.
Baking Soda- Acidic Ammonia- Basic Vinegar- basic Milk- acidic Lemon juice- acidic Coffee- acidic Water- neutral Dish soap- basic Mouth wash- Acidic Toothpaste- Acidic Laundry detergent-
basic
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ANALYSIS AND CONCLUDE Which group
contains items used for cleaning or for personal hygiene?
During the experiment, I noticed that the items used for cleaning are almost always Basic solutions, and the ones that we use for personal hygiene, (i.e. mouthwash, toothpaste, etc) are almost always acidic!