Download 7 rocks and minerals

7 ROCKS AND MINERALS
I.
Multiple choice questions: Tick (3) the correct choice.
1. A mineral made of atoms of simple element is
(a) sand,
(b) quartz
(c) gold
(d) clay
2. The rock formed by the cooling of magma under the surface of earth
is
(a) basalt
(b) granite
(c) limestone (d) haematite
3. The example of sedimentary rock is
(a) granite
(b) basalt
(c) limestone (d) marble
4. The example of metamorphic rock is
(a) basalt
(b) dolomite (c) marble
(d) shale
5. The hardest gemstone is
(a) ruby
(b) sapphire
(c) black diamond (d) emerled
6. Cuprite is an ore of
(a) aluminium (b) iron
(c) copper
(d) calcium
7. Symbiotic bacteria are formed in the roots of
(a) cereal plants
(b) pod bearing plants
(c) cotton plants
(d) none of these
8. A mineral from which a metal can be profitably extracted is called
(a) ore
(b) basalt
(c) magma
(d) granite
9. Limestone and marble are rich in
(a) mica
(b) sand
(c) calcium
(d) quartz
10. Pudding stone is the name given to
(a) conglomerate
(b) quartzite
(c) basalt
(d) tuff
11. The earth crust is made up of
(a) rocks
(b) mineral
(c) silicon and aluminium
(d) all the above
12. Scientists who study about rocks and the crust of the earth are called
(a) zoologists
(b) geologists
(c) paleontologists
(d) none of these
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13. During volcanic eruptions, this molten material is continually ejected
to the surface of the earth:
(a) Magma
(b) Lava
(c) Volcanic ash (d) Pumice
14. Which one of these is formed from the foam on the top of the lava
stream when lava cools down quickly?
(a) Pumice
(b) Obsidian (c) Basalt
(d) Tuff
15. Which one of these is present in granite rock?
(a) Amethyst
(b) Garnet
(c) Malachite (d) Ruby
16. Taj Mahal is made up of
(a) white granite
(b) calcium carbonate
(c) sandstone
(d) slate
17. Minerals make up
(a) rocks
(b) elements
(c) substances
(d) metallurgy
Ans. 1. (c) 2. (b) 3. (c) 4. (c) 5. (c) 6. (c) 7. (b) 8. (a) 9. (c) 10. (a)
11. (d) 12. (b) 13. (a) 14. (a) 15. (b) 16. (b) 17. (a).
II.
Define these terms.
1. Mineral 2. Sedimentary rock 3. Igneous rock 4. Metamorphic rock 5.
Fossil fuel 6. Magna 7. Ore 8. Erosion 9. Non-renewable sources of
energy.
1. Mineral: Minerals are naturally occurring inorganic substances
which may be made of single element or more than one element.
2. Sedimentary rock: The rocks formed by the decomposition of
particles (sediments) by the flowing water or blowing wind are called
sedimentary rocks.
3. Igneous rocks: The rocks formed by the cooling and solidification of
extremely hot motion materials of the earth are called igneous rocks.
4. Metamorphic rocks: The rocks formed by the intense heat and
pressure on the sedimentary rocks, such that their structure and
texture changes are called metamorphic rocks.
5. Fossil fuel: Fuels which are preserved in the earth’s crust as remains
of dead plants and animals are called fossil fuels.
6. Magma: The extremely hot molten material within the interior of the
earth, which is under high pressure, is called magma.
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7. Ore: A mineral from which a metal can be extracted profitably is
called an ore.
8. Erosion: The loss of the topmost layer of soil by the action of wind
and water is called erosion.
9. Non-renewable sources of energy: The sources of energy which
cannot be produced again within a reasonable span of time are called
non-renewable sources of energy.
III. Write short notes on the following.
1. Properties of minerals 2. Tuff 3. Grems 4. Quazite
Ans. Properties of minerals:
(a) Minerals have a definite chemical composition.
(b) Each mineral has a characteristic crystalline structure.
(c) Sometimes, a mineral can have two or more different crystalline
structures depending upon how they are formed in nature.
(d) Minerals have a characteristic lustre, colour, hardness and
specific gravity.
2. Tuff: Sometimes lava is ejected out of a volcano with such a force that
it goes high up into the air which hardens into small pieces of rock
before it reaches the ground. Sometimes, these are cemented together
to form a solid rock. The rock formed in this way is dull grey. It is
called tuff.
3. Gems: Precious stones found in rocks, like garnet in granite rock, are
called gems. They are used in jewellery because of their brilliance and
colour.
4. Quartize. Sandstones gradually change to quartzite. It is so hard that
paving stones are sometimes made of it.
IV.
Complete the following sentences with appropriate terms/phrases:
a. The scientists who study rocks are called _______ .
b. The nature of the magma determines the _______ .
c. The largest deposits of sediments can be found in the _______ .
d. Metals that occur in minerals in the form of elements are called
_______ .
e. Constant exposure to wind and rain causes soil _______ .
f. Decayed organic material found in soil is called _______ .
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Ans. a. Geologists b. kind of igneous rocks c. river or seabeds d. native
elements e. erosion f. humus.
V.
Match the following rocks / minerals with their uses:
(a) Granite
(i) Diamonds
(b) Limestone
(ii) Plaster of Paris
(c) Kimberlite
(iii) Building material
(d) Slate
(iv) Cement
(e) Gypsum
(v) Silicon chips
(f) Quartz
(vi) Roofs
Ans. a. (iii) b. (iv) c. (i) d. (vi) e. (ii) f. (v)
VI. Give four examples for each of the following:
(a) Igneous rocks (b) Sedimentary rocks (c) Metamorphic rocks
(d) Precious stones (e) Semi-precious stones.
(a). Igneous rocks: Granite, basalt, pumice and obsidian.
(b). Sedimentary rocks: Sandstone, dolomite, shale and limestone.
(c). Metamorphic rocks: Marble, slate, quartzite and gneiss.
(d). Precious stones: Diamond, ruby, sapphire and emeralds.
(e). Semi-precious stones: Agate, tiger’s eye, amethyst and rose quartz.
VII. Differentiate between:
(i) Metamorphic and igneous rocks (ii) Soil and sediments (iii) Coal and
petroleum (iv) Clay and sand
(i) The rocks formed by the cooling and solidification of extremely hot
molten materials of the earth are called igneous rocks while the rocks
formed by the intense heat and pressure on the sedimentary rocks,
such that their structure and texture changes are called metamorphic
rocks.
(ii) Soil is the uppermost layer of land mass, which acts as a supporting
medium for the growth of plants while the particles which are
deposited from one place to another by the action of wind or water
are called sediments.
(iii) Coal and Petroleum: Coal is formed when huge forest areas got
buried under the surface of the earth by the action of anaerobic
bacteria while petroleum is formed by the anaerobic decomposition
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of extremely small sea animals and plants which got buried under the
surface of the earth.
(iv) Clay particles are below 0.002 mm in size, have very little air and can
hold a large amount of water. Size of sand particles is between 0.02
mm to 0.20 mm. They have very large amount of air and cannot hold
water.
VIII. Give reasons:
(a) Igneous rocks are used extensively for construction purpose.
Ans. Igneous rocks are very hard. Hence, they are used extensively for
construction purposes.
(b) Wide areas of rock changed when mountains were formed.
Ans. In areas of extreme temperature, where hot day temperatures are
followed by cold night temperatures, it leads to crack in rocks. In
areas of cold temperature, water that seeps into the cracks freezes. As
water expands on freezing, it widens the crack. Thus, wide areas of
rock changed and mountains were formed.
(c) Earthworms are called nature’s gardeners.
Ans. Earthworm helps to keep the soil fertile by their burrowing which
aerates the soil. So, earthworms are called nature’s gardeners.
(d) Coal and petroleum are non-renewable sources of energy.
Ans. There is only a limited supply of coal and petroleum in nature. Once
they are used up, they cannot be replaced. So, they are called nonrenewable sources of energy.
IX. Match the statements in Column A with Column B.
Column A
1. An ore of aluminium metal.
2. An ore of iron metal.
3. A mineral from which a metal is
extracted.
4. A rock formed by the cooling of
magma under the surface of the earth.
5. A soil containing 70% or more of clay.
6. A black stony substance used as a fuel.
7. The phenomenon which results in the
formation of soil.
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Column B
(a) Haematite
(b) Bauxite
(c) Clayey soil
(d) Rock
(e) Granite
(f) Weathering
(g) Coal
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8. A hard substance formed by the
assembly of one or more inorganic
minerals.
(h) Ore
Ans. 1. (b) 2. (a) 3. (h) 4. (e) 5. (c) 6. (g) 7. (f) 8. (d).
X.
Column A
1.
2.
3.
4.
5.
6.
Column B
Combination of minerals
Calcium carbonate
Inorganic substances in the earth’s crust
Flowing magma
Humus
Amber rocks
(a)
(b)
(c)
(d)
(e)
(f)
organic matter
minerals
marble
obsidian
lava
rocks
Ans. 1. (f) 2. (c) 3. (b) 4. (e) 5. (a) 6. (d).
XI.
Write true or false in front of the following statements:
1. Coal is a prehistoric fuel, commonly called fossil fuel.
2. Diamond is used for making jewellery.
3. Granite is an example of igneous rock.
4. Humus is the waste created by dead plants and has no soil value.
5. Marble is a metamorphic rock.
6. Clayey soils are best for agriculture.
7. Soil is formed due to erosion by heat, wind and water.
8. Minerals are useful compounds formed by microbes.
Ans. 1. T 2. T 3. T 4. F 5. T 6. F 7. T 8. F.
XII. Write true or false for the given statements. Rewrite the false
statements correctly.
1. Basalt is a coarse grained hard rock.
Ans. False. Basalt is a fine grained hard rock.
2. Dolomite is formed due to the deposition of magnesium bicarbonate.
Ans. False. Dolomite is formed due to the deposition of calcium carbonate
and magnesium carbonate.
3. The preserved relics of past found in igneous rocks are called fossils.
Ans. False. The preserved relics of past found in sedimentary rocks are
called fossils.
4. Marble is an example of sedimentary rock.
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False. Marble is an example of metamorphic rock.
Plaster of Paris is used in the manufacture of cement.
False. Lime is used in the manufacture of cement.
Bauxite is an ore of copper.
False. Bauxite is an ore of aluminium.
Loamy soils contain 60% – 70% of clay particles and are very
porous.
False. Clayey soils contain 60% – 70% of clay particles and are not
porous.
The size of silt particles is between 0.02 mm to 0.20 mm.
False. The size of silt particles is between 0.002 mm to 0.02 mm.
Oxygen, silicon, aluminium and iron are the common elements
present in the hydrosphere.
False. Oxygen, silicon, aluminium and iron are the common elements
present in the lithosphere.
Metamorphic rocks are formed when layers of rock pieces and
eroded soil get squeezed together.
False. Sedimentary rocks are formed when layers of rock pieces and
soil get squeezed together.
Organic matter buried long ago under extremely high temperature and
pressure turns into coal, peat and amber.
False. Organic matter buried long ago under extremely high
temperature and pressure turns into coal and petroleum.
Granite is a common igneous rock.
True
Bauxite is an ore of calcium.
False. Bauxite is an ore of aluminium.
Rocks are made up of different types of minerals.
True
All ores are minerals but all minerals are not ores.
True
Marble is a calcium rich rock.
True
XIII. Complete the given sentences.
1. A hard substance formed by the assembly of one or more ..................
minerals, is called a rock.
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2. Shale is formed due to the .................. of fine clay.
3. The extremely hot and molten material within the surface of the earth
is called .................. .
4. Coal and petroleum are called .................. fuels.
5. Soils having 70% – 80% of .............. particles are called sandy soils.
6. .................. is an ore of copper.
7. .................. are used for making expensive watches.
8. .................. is used for making talcum powder.
9. .................. are identified by their colour, lustre and hardness.
10. An .................. is a .................. from which one or more metals can be
extracted.
11. .................. are made up of different combinations of minerals.
12. Sediments are generally formed .................. .
13. Granite is usually formed .................. .
14. .................. is the external rock crust of the earth.
15. The three types of rocks are .................. , .................. and metamorphic.
16. Preserved remains of plants and animals are called ................ .
17. Shale smells like .................. when wet.
Ans. 1. inorganic 2. deposition 3. magma 4. fossil 5. sand 6. Malachite
7. Gems 8. Talc 9. Minerals 10. ore, mineral 11. Rocks 12. under water
13. underground 14. lithosphere 15. igneous, sedimentary 16. fossils
17. mud.
XIV. Find out the odd one out. Give a reason for your answer.
1. Cuprite, quartz, haematite and bauxite
Ans. Haematite, bauxite and cuprite are metallic ores is while quartz is a
non-metallic mineral of metamorphic rocks.
2. Shale, marble, dolomite and sandstone
Ans. Shale, sandstone and dolomite are examples of sedimentary rocks
while marble is an example of metamorphic rock.
3. Slate, granite, marble and quartz
Ans. Slate, marble and quartz are examples of metamorphic rocks while
granite is an example of igneous rock.
4. Ruby, graphite, sapphire and emerald
Ans. Ruby, sapphire and emerald are gemstones while graphite is not a
gemstone.
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5. Sandstone, conglomerate, limestone, slate, coal and shale
Ans. Sandstone, conglomerate, limestone, slate and shale are examples of
rocks while coal is a fossil fuel.
6. Pumice, obsidian, basalt, tuff, coal and granite
Ans. Pumice, obsidian, basalt, tuff and granite are examples of igneous
rocks while coal is an example of sedimentary rocks.
7. Slate, quartzite, marble, sandstone, schist and gems
Ans. Slate, quartzite, marble, sandstone and schist are examples of
metamorphic rocks while gems are crystals of ornamental value.
8. Quartz, feldspar, mica, bauxite, gypsum and talc
Ans. Feldspar, mica, quartz, gypsum and talc are non-metallic minerals
while bauxite is a metallic ore.
9. Bauxite, pitchblende, haematite and quartz
Ans. Bauxite, pitchblende, and haematite are metallic ore while quartz is a
non-metallic mineral.
XV. Answer the following questions :
1. (i) What is a rock?
(ii) What is an igneous rock?
(iii) Briefly explain how the following rocks are formed: (a) granite
(b) basalt.
Ans. (i) Rock is a hard substance formed by the assembly of one or more
inorganic minerals.
(ii) The rocks formed by the cooling and solidification of extremely
hot molten materials of the earth are called igneous rocks.
(iii) (a) Formation of granite: When the magma rising up through the
interior of the earth, solidifies beneath the surface of the
earth, the coarse grained rock so formed is called granite.
(b) Formation of basalt: Basalt rock is formed from the lava
which flows out of the surface of the earth and then cools
slowly.
2. Define sedimentary rock and give four examples.
Ans. The rocks formed by the deposition of particles (sediments) by the
flowing water or blowing wind are called sedimentary rocks. For
example, mudstone, shale, sandstone and limestone.
3. Define metamorphic rock. Give two examples of metamorphic rock.
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Ans. The rocks that are formed by the intense heat and pressure on the
sedimentary rocks, such that their structure and texture changes are
called metamorphic rocks. Slate and marble are examples of
metamorphic rocks.
4. (i) What do you understand by the term mineral?
(ii) State three characteristics of minerals.
Ans. (i) Minerals are naturally occurring inorganic substances which may
be made of atoms of a single element or more than one element,
but having a definite composition.
(ii) Characteristics of minerals.
1. Minerals have a definite chemical composition.
2. Each mineral has a characteristic crystalline structure, which
depends upon the arrangement of atoms in three dimensional
pattern.
3. Minerals have a characteristic lustre, colour, hardness and
specific gravity.
5. (i) What is the difference between a diamond and a gem?
(ii) State two uses of gems, in addition to their use as precious
stones.
Ans. (i) Diamond is a transparent form of crystalline carbon. It is highly
priced and is used for making jewellery. While artificial gems
can be prepared by heating aluminium oxide to a very high
temperature. They are used in making expensive watches.
(ii) Uses of gems:
(a) Gems are used in making expensive watches.
(b) They are also used in laser technique.
6. (i) State any two uses of common salt.
(ii) State any two uses of Plaster of Paris.
(iii) Name the mineral from which lime is prepared. State any two
uses of lime.
Ans. (i) Uses of common salt:
(a) Its purified form is used as table salt.
(b) It is used for preserving fish, meat and also in pickles.
(ii) Uses of Plaster of Paris:
(a) It is used for plastering fractured bones.
(b) It is used for preparing moulds for statues.
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(iii) Lime is prepared by strongly heated limestone. Uses of lime.
(a) It is used for white washing purposes.
(b) It is used in the manufacture of cement.
What do you understand by the term soil?
Soil is the uppermost layer of landmass of the earth, which acts as a
life supporting medium for the growth of plants.
Name one important ore of (a) aluminium, (b) iron, (c) copper.
(a) Bauxite is an ore of aluminium.
(b) Haematite is an ore of iron.
(c) Cuprite is an ore of copper.
Name the four important constituents of the top soil.
The four important constituents of soil are:
1. Soil particles of different sizes
2. Humus
3. Soil water
4. Soil air
Name the types of particles of soil in the decreasing order of size.
The types of soil particles in the decreasing order of size are gravel,
coarse sand, fine sand, silt and clay.
What is humus? Why is its presence important for the plants?
Humus is formed from the dead plants and animals by the activity of
microorganisms present in the soil. Presence of humus is important
for plants because it contains all the nutrients which are required for
the growth of plants.
Briefly explain the following: (i) sandy soils, (ii) clayey soils,
(iii) loamy soils.
(i) Sandy soils: Soils having 70 – 80% of sand particles are called
sandy soils. They are highly porous with a lot of air. They cannot
retain water and lack humus. They are not suitable for the growth
of plants.
(ii) Clayey soils: Soils having more than 70% clay particles and
very little sand particles are called clayey soils. These soils have
very little air and can hold a large amount of water. These soils
are also not much suitable for the growth of plants.
(iii) Loamy soils: These soil contain a balanced amount of clay and
sand particles and contain a good amount of humus. They contain
a sufficient amount of air and water. These soils are best for the
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13.
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growth of plants.
Briefly explain the importance of water soluble nitrogen compounds
in the fertility of soil.
Plants need nitrogen in the form of water soluble nitrogen compounds
for the manufacture of amino acids and proteins. This protein
constitute the protoplasm of the plant cells and help in their growth
and development.
How does the soil get enriched with water soluble nitrogen
compounds (i) in nature, (ii) with the help of farmer.
(i) Nature. Nature compensates nitrogen in two ways:
(a) By thunder and lightening: When lightening occurs, nitrogen
and oxygen combine to form nitric oxide gas. This gas further
reacts with oxygen to form nitrogen dioxide. It dissolves in
water to form nitric acid. When it rains, nitric acid is washed
down to the earth where it reacts with calcium carbonate to
form calcium nitrate and hence make the soil fertile.
(b) By symbiotic bacteria: Root nodules of pod bearing plants
contain symbiotic bacteria, which directly absorb nitrogen
from the air and convert it into soluble compounds of
nitrogen.
(ii) By farmer: Farmers supply manure and artificial fertilisers such
as urea, etc. in adequate amount to get the soil enriched with
water soluble nitrogen compounds.
Briefly explain how coal is formed in nature?
Coal is formed from the huge forests which got buried under the
surface of the earth, under humid and hot conditions, by the action of
anaerobic bacteria.
Briefly explain how petroleum is formed in nature?
Petroleum is formed by the anaerobic decomposition of extremely
small sea animals and plants which got buried under the surface of the
earth millions of years ago.
Name a few problems created by the excessive use of fossil fuels.
Excessive use of fossil fuels led to the increase in the amount of
carbon dioxide in the atmosphere by which theaverage temperature of
the earth is gradually increasing. In addition to it, poisonous gases
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such as nitrogen dioxide, sulphur dioxide and carbon monoxide are
added into the atmosphere which are very harmful.
18. What factors bring about changes in pre-existing rocks?
Ans. Excess heat, frost, wind, high pressure and temperature, sideways
pushing and rain are some factors that bring about changes in preexisting rocks.
19. What type of rock is basalt? Why is it used to make tools?
Ans. Basalt is a type of igneous rock which is formed from the lava which
cools rather slowly. Basalt has sharp edges; so it is used to make
tools.
20. What are ores? Name the ores of iron and aluminium.
Ans. A mineral from which a metal can be extracted profitably is called an
ore. Bauxite is an ore of aluminium and haematite is an ore of iron.
XVI. Answer in a sentence or two.
(a) How are rocks classified?
Ans. Rocks are classified into igneous, sedimentary and metamorphic
rocks, based on how they are formed.
(b) Mention two uses of sedimentary rocks.
Ans. Limestone and shale are example of sedimentary rocks.
(i) Limestone is used for making cement.
(ii) Shale is used for making drainpipes.
(c) Why are some minerals highly valued as gems?
Ans. Some minerals are extremely rare, attractive as well as durable, so
they are highly valued as gems.
(d) Name the ores from which the following metals are obtained:
(i) Aluminium (ii) Copper (iii) Iron (iv) Lead
Ans. (i) Aluminium is obtained from bauxite.
(ii) Copper is obtained from cuprite.
(iii) Iron is obtained from haematite.
(iv) Lead is obtained from galena.
(e) What is the effect of erosion on rocks?
Ans. Rocks are broken into small pieces by the action of wind, rain and
changes in temperature. This is called erosion.
(f) Mention the three types of soil.
Ans. Clay, sand and loam are the three types of soil.
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(g)
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(i)
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(j)
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In which kind of rocks are fossils most likely to be found?
Fossils are most likely to be found in sedimentary rocks.
Why are coal and petroleum called fossil fuels?
Coal and petroleum are called fossil fuels because they are formed
from the remains of plants and animals that lived million of years ago.
List the uses of coal and petroleum.
Coal and petroleum are major sources of energy. They are used for
making plastics, drugs, dyes and detergents.
Name four renewable sources of energy.
Energy from the sun, water, wind, ocean tides and waste from animals
and plants are renewable sources of energy.
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