You are given a sample of a solution. How would you check the possibility of it being an iodine solution?
To check if the solution is iodine, take a food item known to contain starch (such as a slice of potato, bread, or boiled rice).
Place a small piece of the food item on a dish. Using a dropper, put 2-3 drops of the given solution on the food item. Observe the colour change.
If the food item turns blue-black, the solution is iodine solution because iodine reacts with starch to produce a blue-black colour.
If there is no colour change, the solution is not iodine.
Explanation
The chapter describes in Activity 3.5 how to test for starch using iodine solution. The test states that 'a blue-black colour indicates the presence of starch.' This same test can be used in reverse—if we have a known starch-containing food item and an unknown solution, the blue-black colour change confirms the presence of iodine in the solution.
Solution Steps
Take a food item known to contain starch (such as potato, bread, or boiled rice)
Place a small piece of the food item on a dish
Put 2-3 drops of the given solution on the food item using a dropper
Observe the colour change
Blue-black colour confirms iodine solution; no colour change means it is not iodine