The property which forms the basis of sieving

Correct Answer:

d) Difference in size

Sieving is one of the oldest and simplest methods of separating substances from a mixture. The process involves passing the mixture through a sieve or mesh that has tiny holes of uniform size. When the mixture is shaken or moved across the sieve, the smaller particles pass through the holes, while the larger ones remain on the sieve. Thus, the separation is achieved based on a difference in particle size.

This principle is commonly applied in both household and industrial processes. For example, in our kitchens, sieving is used to separate finer flour from coarser particles or husk. The flour particles, being smaller in size, easily pass through the sieve, while the larger impurities remain behind. Similarly, in construction, sieving is used to separate fine sand from stones or gravel to ensure uniformity of material.

Let’s analyze the given options one by one:

1. Difference in weight – While weight plays an important role in some separation methods like winnowing or centrifugation, it is not the basis of sieving. The sieve does not measure or act upon the weight of the particles but only their size relative to the openings in the mesh.
2. Difference in shape – The sieve does not differentiate based on whether particles are round, irregular, or elongated. If the particle’s size is smaller than the hole in the sieve, it will pass through regardless of its shape.
3. Difference in colour – Colour has no role in the process of sieving. Even if two substances have different colours, they will not be separated by a sieve unless their particle sizes differ.
4. Difference in size – This is the correct basis. The mesh acts as a filter that only allows particles of certain sizes to pass through. Larger particles remain on the mesh, achieving separation.

In scientific and industrial applications, sieving is also used in pharmaceuticals, food processing, mining, and chemical industries to ensure proper granule size for production or consumption. For example, in the pharmaceutical industry, powders must meet specific particle size standards to ensure proper mixing and drug delivery.

Thus, sieving is a method grounded purely on size differences of particles, making it a very practical, efficient, and cost-effective method for separation.

Final Answer: The property which forms the basis of sieving is difference in size.