RED CABBAGE PH INDICATOR

THE PURPOSE OF THIS EXPERIMENT IS TO SHOW HOW TO MAKE YOUR OWN PH INDICATOR USING CABBAGE JUICE

Why use cabbage juice? By boiling the red cabbage leaves, we extracted a class of pigment molecules called anthocyanins into solution. Anthocyanin molecules will change their color depending upon the pH of their environment and can indicate the pH of a solution.

What is pH? The pH scale measures how acidic or basic a substance is. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic.

What is the pH scale? The pH scale measures how acidic or basic a solution is.

Red Cabbage pH scale neutral Strong acid Strong alkali

Investigation Identify each solution as either an acid, base, or neutral.

Solution 1 Vinegar pH: 3-4 (acid)

Solution 2 Soda pH: 3 (acid)

Solution 3 Tap Water pH: 7 (neutral)

Solution 4 Baking Soda pH: 8-9 (base)

Solution 5 Milk pH: 6 (acid)

Solution 6 Soapy Water pH: 12 (base)

Solution 7 Lemon Juice pH: 2-3 (acid)

Solution 8 Hand Sanitizer pH: 7 (neutral)

RED CABBAGE JUICE CAN BE USED TO TEST THE PH OF COMMON HOUSEHOLD CHEMICALS. RED CABBAGE JUICE CONTAINS A NATURAL PH INDICATOR THAT CHANGES COLORS ACCORDING TO THE ACIDITY OF THE SOLUTION.

Add a lemon to the glass of cabbage juice We noticed the color changed to red, which indicated that lemon juice is classified as an acid.

Add a little vinegar to the glass of cabbage juice We noticed the color changed to red, which indicated that vinegar is classified as an acid.

Add a teaspoon of laundry detergent to the glass of cabbage juice We noticed the liquid turns green, indicating that this chemical is a base.

Add a teaspoon of oven cleaner to the glass of cabbage juice We noticed the color changed to green, which indicated that the oven cleaner is classified as an base.

Add a teaspoon of alka-prim tablets to the glass of cabbage juice We noticed the color changed to green, which indicated that alka-prim tablets are classified as an base.

DURING OUR EXPERIMENT THE PURPLE CABBAGE JUICE TURNED RED WHEN IT WAS MIXED WITH SOMETHING ACIDIC AND TURNED GREEN WHEN IT WAS MIXED WITH SOMETHING BASIC. RED CABBAGE JUICE IS CONSIDERED TO BE AN INDICATOR BECAUSE IT SHOWED US SOMETHING ABOUT THE CHEMICAL COMPOSITION OF OTHER SUBSTANCES.

RED CABBAGE CONTAINS A WATER-SOLUBLE PIGMENT CALLED ANTHOCYANIN THAT CHANGES COLOR WHEN IT IS MIXED WITH AN ACID OR A BASE. THE PIGMENT TURNS RED IN ACIDIC ENVIRONMENTS WITH A PH LESS THAN 7 AND THE PIGMENT TURNS BLUISH-GREEN IN ALKALINE (BASIC) ENVIRONMENTS WITH A PH GREATER THAN 7.

Characteristics Of Acids Acids can be characterized by: 1.A sour taste. 2.It turns blue litmus paper red 3.It tastes sour. Try drinking lemon juice (citric acid)

Characteristics of Bases A Base is characterized by: 1.A bitter taste. (Milk of Magnesia) 2.It feels slippery. (Soapy Water) 3.It turns Red Litmus Blue.

Why Learn about Acids & Bases? What do you think is the pH level of NYC tap water? The pH of a swimming pool must be checked periodically. Why? Is it important for Lakes & Rivers to maintain a certain pH?

Properties of an Acid  Tastes Sour  Conduct Electricity  Corrosive, which means they break down certain substances. Many acids can corrode fabric, skin,and paper  Some acids react strongly with metals  Turns blue litmus paper red Picture from BBC Revision Bites _1.shtml _1.shtml

Uses of Acids  Acetic Acid = Vinegar  Citric Acid = lemons, limes, & oranges. It is in many sour candies such as lemonhead & sour patch.  Ascorbic acid = Vitamin C which your body needs to function.  Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics.  Car batteries

What is a base?  A base is a solution that has an excess of OH- ions.  Another word for base is alkali.  Bases are substances that can accept hydrogen ions

Properties of a Base  Feel Slippery  Taste Bitter  Corrosive  Can conduct electricity. (Think alkaline batteries.)  Do not react with metals.  Turns red litmus paper blue.

Acid – Base Reactions  A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.