pH INDICATOR

MATERIALS

Red cabbage
Sugar water
Baking soda
Vinegar
Cups (clear plastic, or paper)
Knife and pan
Stovetop

SAFETY PRECAUTIONS

Should be supervised by an adult due to the chopping with a knife and heating on a stovetop.

PROCEDURE

1. Chop a few leaves of red cabbage finely and place in pot. Cover with water, bring to boil, reduce heat, and simmer until solution is deep blue/purple.
2. Allow cabbage solution to cool. Strain into a jar. After the experiment is over, be sure to save this solution for other experiments. It saves well, covered, in the refrigerator. This is your indicator. If you wish, you may also take strips of white filter paper (such as a coffee filter cut into strips 2-3 inches long) and soak in the juice, and then let dry, to use as indicator strips to experiment with. Still save the juice, however.
3. Explain the term ‘indicator.’ (a substance that indicates if something is acidic or basic.)
4. Mix baking soda with a little water in a cup to make a baking soda/water solution. Label “baking soda”.
5. Pour a small amount of sugar water into another cup and label “sugar water”.
5. Pour a small amount of vinegar into a third cup and dilute with a little water. Label “vinegar”.
6. Ask, “What do you think will happen if we pour our cabbage juice/indicator into these cups?”
7. Add cabbage juice/indicator into each of the 3 cups, recording observations on the chart provided.
8. Discuss acids and bases and how they react with the cabbage juice indicator. Discuss neutral solutions and how they react with the indicator.

EXPLANATION

Cabbage juice is an indicator that indicates if a substance is acid, base, or neutral. If a substance is an acid, the cabbage juice (or strip) will turn pink or red. If a substance is a base, the cabbage juice will turn green or blue-green. If a substance is neutral, the cabbage juice/indicator will not change color. The vinegar is an acid and will turn pink. The baking soda is a base and will turn green.

Gas Matters

Kids love this dynamic demonstration. Easy and effective!

MATERIALS

Baby food jar
Carbonated water (or clear carbonated soda)
1 tsp table salt

PROCEDURE

1. Fill baby food jar ½ full with carbonated clear liquid.
2. Ask, “Do you think carbon dioxide gas is considered ‘matter’?” “How do you define ‘matter’?” (Has mass and takes up space.)
3. Ask, “What do you think will happen if we add some salt to this jar?”
4. Add 1 teaspoon of table salt to the jar. Observe. Ask, “Why do you think this happened?”

EXPLANATION

The bubbles in the carbonated liquid are full of carbon dioxide. Carbon dioxide gas takes up space. When you add the salt molecules, the salt molecules push the carbon dioxide molecules out of the way. When the carbon dioxide bubbles rise to the top, they bring small amounts of soda with them. Replacing a gas with another substance is called “effervescence.” Gas is considered ‘matter’ because it fulfills the two requirements: it takes up space, and, it has mass (weight).