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

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

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.

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

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 cm3 -100 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.

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

Check Test

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