IDENTIFYING PH USING NATURAL

SOURCES AS INDICATORS

La’Darion Roberts

Period 3

LaSalle

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.

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

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.

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

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.

PROCEDURE Repeat Step 4 for

household items: Lemon Juice, 2% Milk, Coffee, Mouthwash, Toothpaste, distilled water, laundry detergent(powder), dish washing soap

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.

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)

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

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!