Detailed, Step-by-Step NCERT Solutions for Class 11 Geography Chapter 5 Minerals and Rocks Questions and Answers were solved by Expert Teachers as per NCERT (CBSE) Book guidelines covering each topic in chapter to ensure complete preparation.
Minerals and Rocks NCERT Solutions for Class 11 Geography Chapter 5
Minerals and Rocks Questions and Answers Class 11 Geography Chapter 5
Question 1.
Multiple choice questions.
(i) Which one of the following are the two main constituents of granite?
(a) Iron and Nickel
(b) Iron and Silver
(c) Silica and Aluminium
(d) Iron oxide and Potassium
Answer:
(c) Silica and Aluminium.
(ii) Which one of the following is the salient feature of metamorphic rocks?
(a) Changeable
(b) Quite
(c) Crystalline
(d) Foliation
Answer:
(a) Changeable.
(iii) Which one of the following is not a single element mineral?
(a) Gold
(b) Silver
(c) Mica
(d) Graphite
Answer:
(c) Mica.
(iv) Which one of the following is the hardest mineral?
(a)Topaz
(b) Diamond
(c) Quartz
(d) Feldspar
Answer:
(b) Diamond.
(v) Which one of the following is not a sedimentary rock?
(a) Tillite
(b) Borax
(c) Breccia
(d) Marble
Answer:
(a) Tillite.
Question 2.
Answer the following questions in about 30 words each :
(i) What do you mean by rocks? Name the three major classes of rocks.
Answer:
A rock is an aggregate of one or more minerals. It may be soft or hard and in varied colours.
Three classes of rocks are :
- Igneous rocks
- Sedimentary rocks, and
- Metamorphic rocks.
(ii) What is an igneous rock? Describe the method of formation and characteristics of igneous rock.
Answer:
The solid form of the magma is known as igneous rocks. These rocks are formed from lava hurled out of a volcano or from the cooling of the magma below the crust.
Characteristics:
- These are massive and found in bulks.
- These rocks have different types of crystals.
- These rocks are formed due to the cooling of magma.
(iii) What is meant by sedimentary rock? Describe the mode of formation of sedimentary rock?
Answer:
The rocks which are formed by the accumulation of sediments are known as sedimentary rocks. These are formed by sediments brought by the erosion and weathering of other rock types. When deposited in sea, they are compressed and hardened to form layers of rocks. Sandstone is made from grains of sand which have been naturally cemented here.
(iv) What relationship explained by rock cycle between the major type of rock?
Answer:
Rock cycle is a continuous process through which old rocks are transformed into new ones. Igneous rocks are primary rocks and other are rocks formed from these. They can be changed into metamorphic rocks. The fragments derived out of igneous and metamorphic rocks form into sedimentary rocks.
The sedimentary rocks can turn into fragments and the fragments can form sedimentary rocks. The crustal rocks once formed may be carried down into the mantle through subduction process and melt down due to the increase in temperature in the interior and turn into molten magma, the original source of igneous rocks.
Question 3.
Answer the following questions in about 150 words each :
(i) Define the term ‘mineral’ and name the major classes of minerals with their physical characteristics.
Answer:
A mineral is an inorganic element or compound having definite chemical composition and definite atomic structure. All the commonly occuring minerals are classified into six major mineral groups that are known as major rock forming minerals.
Physical characteristics :
(1) External crystal structure : They have six types of crystal structure – cubes, octahedrons, hexagonal prisms, etc.
(2) Cleavage : They undergo cleavage in one or more direction and, at any angle to each other.
(3) Fracture : The crystal will break in an irregular manner, not
along the plane of cleavage. ‘
(4) Lusture : Each mineral has a distinctive lusture like metallic, silky, glossy, etc.
(5) Colour: Some minerals have characteristic colour determined by their molecular structure – malachite, azurite, chalcopyrite, etc. Some minerals are coloured by impurities, such as quartz.
(6) Streak: The colour of the ground powder of any mineral may be the same as the mineral or may differ.
(7)
- Transparency : When light rays pass through the objects, they can be seen plainly.
- Translucent: Light rays pass through but will get diffused, so that object cannot be seen clearly.
- Opaque : Light rays will not pass at all.
(8) Structure: Minerals have particular arrangement of individual crystals : fine, medium or coarse grained.
(9) Hardness: The degree to which a mineral surface resist being scratched is known as hardness.
(10) Specific gravity : It is the ratio between the weight of a given object and the weight of an equal volume of water.
(ii) Describe the nature and mode of origin of the chief types of rocks at the earth’s crust. How will you distinguish them?
Answer:
A rock is an aggregate of one or more minerals. There is a close relationship between rocks and landforms. The rocks are grouped under three types of categories :
- Igneous rocks
- Sedimentary’ rocks
- Metamorphic rocks.
Igneous rocks: They form out of magma and lava from the interior of the earth. These are known as primary rocks. They are classified on the basis of texture (structure).
Sedimentary Rocks : These rocks are formed by deposition of fragments of rocks by exogenous processes. Fragments are transported in by various exogenous agencies and deposited through compaction/or cementation. This process is called lithification. Depending upon their mode of formation they are classified into three major groups :
- Mechanically formed
- Organically formed, and
- Chemically formed.
Metamorphic Rocks : These rocks are formed under the action of x pressure, volume and temperature (PVT). Metamorphism is a process ’ by which already consolidated rocks undergo recrystallization and reorganization of materials within original rocks. They are classified into two major groups – foliated and non-foliated rocks.
(iii) What are metamorphic rocks? Describe the types of matamorphic rock and how they are formed.
Answer:
The solid form of the magma is known as igneous rocks. These rocks are formed from lava hurled out of a volcano or from the cooling of the magma below the crust.
Characteristics:
- These are massive and found in bulks.
- These rocks have different types of crystals.
- These rocks are formed due to the cooling of magma.