Sunita took a small food sample of boiled rice in a test tube and added to drops of dilute iodine solution to it. What color change will she observe, and which nutrient's presence is indicated by this test?
Answer
The solution turns blue-black, which confirms the presence of starch (a carbohydrate).
The correct answer is The solution turns blue-black, which confirms the presence of starch (a carbohydrate). — Step 3: Relate the food sample to its nutrient. Boiled rice contains carbohydrates mainly in the form of starch. Therefore, adding dilute iodine solution to boiled rice results in a blue-black color.
Step-by-step solution
- Step 1: Identify the chemical reagent used. Dilute iodine solution is used to test for the presence of starch in food items.
- Step 2: Determine the characteristic color change. When iodine solution comes in contact with starch, it turns into a blue-black color.
- Step 3: Relate the food sample to its nutrient. Boiled rice contains carbohydrates mainly in the form of starch. Therefore, adding dilute iodine solution to boiled rice results in a blue-black color.
Common mistake: Students sometimes write 'violet' instead of 'blue-black'. Violet color indicates the presence of proteins when tested using copper sulphate and caustic soda solution.
Concept tested: Test for Starch
Published · How this solution was prepared and checked