Science Making Indicators

15.05.18

Aim: To make acid-base indicators using everyday substances.

Equipment: Red cabbage, tea, beetroot, turmeric, cranberry juice, a beaker, water, tripod, Bunsen burner, gauze mat, 1.0 mol L-1 NaOH.

Method: 

Task one
For the Tea: Put 100 ml of water into a beaker and boil.
Turn off the Bunsen burner and put three tea bags in the beaker.
Remove tea bags when the tea bags when the tea is very strong.
Place in a small beaker and leave to one side.

For the Cranberry juice: Pour into a beaker and leave to one side.

For the Turmeric: Mix 1 teaspoon turmeric in 100 ml cup of alcohol.
Place in a small beaker and leave to one side.

For the Cabbage: Chop the cabbage into small pieces until you have enough to fill 2 cups.
Place the cabbage in a large beaker and add water to cover the cabbage.
Boil over a Bunsen burner for at least ten minutes for the colour to leach out of the cabbage.
Filter out the plant material to obtain a red-purple-bluish coloured liquid. This liquid is at about pH 7.(The exact colour you get depends on the pH of the water.)
Place in a small beaker and leave to one side.
Repeat this method for the beetroot.

Task two: 
1. You now have five beakers, each containing a different indicator.
2. Using a pipette, place 5 ml of the cabbage indicator into two test tubes.
3. Add 5 ml of HCI (acid) to one test tube and 5 ml of NaOH (Alkali) to the other test tube.
4. Record the colour change in the table below.
5.  Clean the test tubes and repeat for the beetroot, tea, cranberry, and turmeric indicators.

Results:

Indicator	Colour in HCI (Acid)	Colour in NaOH (alkali)
Tea	Orange	Dark violet
Beetroot	Red-orange- peachy	Dirty yellow
Cabbage	Red	Green
Cranberry Juice	Light-rea-pink	Lime-green
Turmeric	Yellow	Red