Chapter 3 · Question 10

Define the terms: mineral, ore, and gangue. Explain how the occurrence of metals in nature is related to their position in the reactivity series. Give examples of metals found in the free (native) state and in the combined state.

Q10

Define the terms: mineral, ore, and gangue. Explain how the occurrence of metals in nature is related to their position in the reactivity series. Give examples of metals found in the free (native) state and in the combined state.

Answer Revealed

Direct Answer:

A mineral is a naturally occurring element or compound in the earth's crust. An ore is a mineral from which a metal can be extracted profitably (i.e., it contains a high percentage of the metal). Gangue refers to the earthy impurities like soil, sand, and silt present in mined ores. Low-reactivity metals (Au, Ag, Pt) are found in the free/native state because they do not react easily. Copper and silver also occur as sulphides or oxides. Medium-reactivity metals (Zn, Fe, Pb) occur as oxides, sulphides, or carbonates. Highly reactive metals (K, Na, Ca, Mg, Al) are never found free — they always exist as compounds because they readily react with other elements.

Simple Explanation

Minerals are the natural chemical compounds in the ground. An ore is a mineral rich enough in metal that it is worth mining for profit. Gangue is the unwanted dirt and sand mixed in with the ore, which must be removed before smelting. The reactivity series explains where you find metals: gold and silver are so lazy (unreactive) that they sit around as pure metals. Copper sometimes does too. But reactive metals like sodium and potassium are never found alone — they are always stuck in compounds because they react with everything around them.

Exam-Ready Structure

The NCERT Chapter 3 introduces the foundational vocabulary of metallurgy (Section 3.4) and links metal occurrence directly to reactivity. 1. Definitions: (a) Mineral: An element or compound that occurs naturally in the earth's crust. All ores are minerals, but not all minerals are ores. (b) Ore: A mineral that contains a very high percentage of a particular metal and from which the metal can be extracted profitably. (c) Gangue: The unwanted earthly impurities such as soil, sand, and silt that contaminate ores when they are mined. These must be separated through enrichment processes before metal extraction. 2. Occurrence and the reactivity series (Fig. 3.9): (a) Metals low in the reactivity series (Au, Ag, Pt, and sometimes Cu) are the least reactive and are found in the free or native state as elements. Cu and Ag also occur in the combined state as sulphide or oxide ores. (b) Metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive and occur mainly as oxides, sulphides, or carbonates. Oxides are very common because oxygen is highly reactive and abundant in the earth's crust. (c) Metals high in the activity series (K, Na, Ca, Mg, Al) are so reactive that they are never found as free elements in nature — they always exist as compounds. 3. The seawater also contains soluble salts of metals such as sodium chloride (NaCl) and magnesium chloride (MgCl₂).

Key Points

Mineral: naturally occurring element/compound; Ore: mineral with high enough metal content for profitable extraction
Gangue: earthy impurities (soil, sand, silt) in mined ores removed before extraction
Low-reactivity metals (Au, Ag, Pt) found in free/native state; Cu found both free and as sulphide/oxide
Medium-reactivity metals (Zn, Fe, Pb) occur as oxides, sulphides, or carbonates
High-reactivity metals (K, Na, Ca, Mg, Al) are NEVER found free — always in combined state

Define the terms: mineral, ore, and gangue. Explain how the occurrence of metals in nature is related to their position in the reactivity series. Give examples of metals found in the free (native) state and in the combined state.