1. UNIT 1 ACIDS, ALKALIS & CHEMICAL REACTIONS Lesson 3 – Homemade Indicators – PART 1

2. Aims of the Lesson
I know that it is possible to make indicators to test for acids/alkalis from substances that could be found in the home.
Indicators can be made from a range of materials including:
Red cabbage
Curry powder
Flowers

3. Red cabbage Indicator
It is possible to make an indicator that will differentiate between acids and alkalis using red cabbage.
In the presence of an acid the indicator will turn red.
In the presence of an alkali the indicator will turn blue/green/yellow, depending on the strength.

4. ACID or ALKALI or NEUTRAL
Red cabbage Indicator
Copy the following table in to your jotter:
SOLUTION
Colour pH
ACID or ALKALI or NEUTRAL
Example
RED 3
Acid
Lemon Juice
Salt Solution
Vinegar
Indigestion tablets
Baking soda
Magnesium hydroxide

5. EXPERIMENT Chop the cabbage up into very small pieces.
Place the chopped cabbage into a beaker and cover with boiling water (BE CAREFUL.)
Allow the cabbage to sit for 5-10 mins or until the colour runs.
Filter the red/purple liquid from the cabbage material. Throw away the cabbage remains and keep the liquid.
Pour 50 cm cm3 of cabbage liquid into several small beakers.
Slowly pour one test material into the beaker and observe the colour change.
Repeat for each test substance.

6. RESULTS Substances tested:
Lemon juice, vinegar, baking soda, indigestion tablets, magnesium hydroxide, salt solution.

7. Check Test

8. EXTENSION ACTIVITY Alien Juice Bar
Can be completed as a class, or in smaller groups.