Question

a dish is given to you, which contains a blackish - yellow powder. when you move a magnet over it, black particles fly upwards and get stuck to the magnet, all thats left in the dish is a yellow powder, which you discover to be sulfur.
was your original powder an element, compound, or mixture explain how you know.

Explanation:

A mixture is a combination of two or more substances that retain their individual properties. In this case, the original powder had two distinct substances - one (the black particles) was magnetic and the other (sulfur) was not. They could be separated by physical means (using a magnet), which is a characteristic of mixtures. Elements are pure substances with only one type of atom, and compounds are substances formed by chemical bonding of two or more elements in a fixed ratio. Since no chemical bonding was involved (as separation was physical) and there were two different substances, it can't be an element or a compound.

Answer:

The original powder was a mixture. We know this because it contained two different substances (the black magnetic particles and sulfur) that could be separated by a physical method (using a magnet), which is a key property of mixtures. Elements are pure substances with only one type of atom, and compounds are formed by chemical bonding of elements in a fixed ratio (no chemical bonding was indicated here as separation was physical).