how can we separate a mixture of safety pins , sand and chalk powder ?

To separate a mixture of safety pins, sand and chalk powder, first bring a magnet near the mixture and safety pins will get separated.

Further take a sieve according to its pore size and the size of sand granules and chalk powder.

If chalk powder is fine and sand granules are bigger, take a sieve with fine and small pore size and filter the mixture through it. The chalk powder will pass through the sieve and sand will be left in the sieve.

If sand granules are smaller as compared to the chalk powder, take a sieve of pore size such that sand passes through it and chalk powder remains.

In this way, all the three substances will be separated.