Select the appropriate options and complete the following paragraph.
(ores, gangue, metallurgy, free, electrolysis, minerals, combined, copper, iron, platinum)
Based on their reactivity, most of the metals are found in ___ state in the earth's crust while some metals such as silver, gold and are found in free state. The compounds of metals which occur naturally in the earth's crust are known as ___ . The minerals from which metals can be profitably extracted are called ___ . Ores mined from earth usually contain large amount of impurities like sand , soil , etc. These impurities are called ___ . The extraction of metals from their ores and then refining them for use is known as _____

Explanation

Based on their reactivity, most of the metals are found in combined state in the earth's crust while some metals such as silver, gold and plantinum are found in free state. The compounds of metals which occur naturally in the earth's crust are known as minerals . The minerals from which metals can be profitably extracted are called ores . Ores mined from earth usually contain large amount of impurities like sand , soil , etc. These impurities are called gangue . The extraction of metals from their ores and then refining them for use is known as metallurgy .