Question

After you have dinner tonight wash your own plate with soap/detergent.
(a)What colour change is observed when soap/detergent is applied?
(b)Name the type of reaction and explain it.

Answer 1

Hint: Soaps and detergents are basic in nature, and in food that we have, there is presence of turmeric, which is a natural indicator and changes its colour according to the presence of acid or base. So thus, acid base reaction or neutralization reaction also takes place.

Complete step by step answer:
In dinner, the food that we take surely has the presence of turmeric in most of the food items, this turmeric we know is a natural indicator for testing the presence of acid or base.
Now, when soap or detergent is used for washing plates, then the turmeric powder remaining along with oil or fats in the plate will react.
(a)Turmeric has yellow colour in its natural state, but when in presence of base changes to orange or red colour, while in acid, no colour change is observed. Here soaps and detergents are basic in nature, so the colour change while washing plates is orange or red with soaps and detergents.
(b)The reaction with turmeric of soaps and detergents is an indicator reaction, in which acid base neutralization takes place and salts are formed. Even the presence of edible oils and fats in food are acidic or alcoholic in nature, so soaps and detergents which are basic in nature, react with each other and neutralisation reaction takes place which gives salt and water.
${\text{Acid + Base}} \to {\text{Salt + Water}}$
This process makes the plates and vessels and even cloths clean, and thus we use soaps or detergents for cleaning purposes.



Note:
Remember the colour of natural indicators in acidic, neutral and basic substances. Even the presence of edible oils and fats are acidic in nature, and soaps/ detergents are basic in nature, so this type of reaction is called neutralisation. The acid and base reacts to form salt and water, this type of reaction is called neutralisation.