What are gravel and sand? Explain the process and applications of sieving.

The materials shown in the picture above are gravel and sand.

Sieving is used to separate mixtures of solid particles of different sizes, or solid particles from a liquid.

Sieving is generally used in various applications such as separating sand particles for building, during cooking and baking, and when making tea.

Sieving works by using a sieve, which has small holes of a specific size. When a mixture is passed through the sieve, smaller particles fall through the holes, while larger particles are retained on the sieve, effectively separating the components based on their size.

The possible reason for sieving the material shown in the picture (gravel and sand) is to separate the larger gravel particles from the finer sand particles. This is often done to obtain sand of a specific fineness for construction purposes, such as making concrete or mortar, or for other applications where uniform particle size is required.