Sieving or mixing them in water then filtration and then evaporation.
chalk powder and water by filtration. sand and water by filtration. grains and stones by hand picking

Separation of Substances

Mustard seeds and common Salt:
1. Crushing: The mixture of mustard seeds and common salt can be crushed using a mortar and pestle. This will break down the seeds into smaller particles.
2. Sieving: After crushing, the mixture can be passed through a sieve. The mustard seed particles will be retained on the sieve, while the smaller salt particles will pass through.
3. Dissolving: The sieved mixture can then be dissolved in water. The salt particles will dissolve, while the mustard seed particles will remain undissolved.
4. Filtration: The mixture can be filtered to separate the undissolved mustard seed particles from the salt solution. The filter paper will trap the mustard seed particles, allowing the salt solution to pass through.

Chalk powder and water:
1. Sedimentation: The mixture of chalk powder and water can be left undisturbed for some time. The heavier chalk particles will settle down at the bottom of the container due to gravity.
2. Decantation: After sedimentation, the water can be carefully poured out, leaving the settled chalk particles behind.
3. Filtration: The remaining chalk particles can be separated from any remaining water by filtration. The filter paper will trap the chalk particles, allowing the water to pass through.

Sand and water:
1. Sedimentation: The mixture of sand and water can be left undisturbed for some time. The heavier sand particles will settle down at the bottom of the container due to gravity.
2. Decantation: After sedimentation, the water can be carefully poured out, leaving the settled sand particles behind.
3. Filtration: The remaining sand particles can be separated from any remaining water by filtration. The filter paper will trap the sand particles, allowing the water to pass through.

Grains and stones:
1. Winnowing: The mixture of grains and stones can be subjected to winnowing. This involves pouring the mixture from a height in front of a gentle breeze or using a fan. The lighter grains will be carried away by the wind, while the heavier stones will fall down.
2. Handpicking: After winnowing, any remaining stones can be separated by handpicking. The grains can be picked out one by one, leaving behind the stones.

By following these methods, mustard seeds can be separated from common salt, chalk powder can be separated from water, sand can be separated from water, and grains can be separated from stones. These separation techniques are based on the differences in physical properties such as size, density, and solubility of the substances involved.