Question

5) How could you get clean sand from a mixture of sand and little bits of
iron wire?
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Answer 1

Depending on the size of iron bits vs. sand granulated.

Use a magnet to attract the ferrous iron particles out of the sand. Depending on scale needed could use an electromagnet.

Answer 2

Crest a filter from the iron wire and pour the mixture down. The clean sand will go through while the parts that are too large (dirty) sand will not pass through the filter