How can natural indicators be prepared? Explain by giving an example.
Natural indicators can be prepared from coloured plant parts such as flower petals, leaves, and roots. The process involves extracting the coloured pigments from these plant materials.
For example, to prepare red rose extract as an indicator: (1) Collect fallen petals of red roses from the surroundings. (2) Wash the petals with water to remove dirt. (3) Crush the petals using a mortar and pestle. (4) Place the crushed petals in a glass tumbler. (5) Pour hot water into the tumbler until the petals are completely immersed. (6) Cover the tumbler with a lid and wait for 5-10 minutes until the water becomes coloured. (7) Filter the mixture to obtain the flower extract.
This red rose extract can be used as an acid-base indicator as it gives red colour in acidic solutions and green colour in basic solutions.
Similarly, turmeric paper can be prepared by dipping filter paper in turmeric paste and drying it.
Explanation
The chapter describes in Activity 2.3 and 2.5 the detailed process of preparing natural indicators from red rose petals and turmeric. These natural substances contain pigments that change colour in response to acidic or basic conditions. The chapter also mentions that beetroot, purple cabbage, Indian blackberry (jamun), and red hibiscus flowers can also be used to prepare natural indicators following similar extraction methods.
Solution Steps
Natural indicators can be prepared from coloured plant parts such as flower petals, leaves, and roots
The process involves extracting coloured pigments from plant materials
To prepare red rose extract: collect petals, wash, crush with mortar and pestle, add hot water, wait 5-10 minutes, and filter
Red rose extract gives red colour in acidic solutions and green colour in basic solutions
Turmeric paper can be prepared by dipping filter paper in turmeric paste and drying it