Textbook Solutions: Rocks and Minerals | Eureka Plus Class 5: Book Solutions, Notes & Worksheets PDF Download

I. Write one word to represent each of the following: 

1. extremely hot substance deep below the Earth's surface ________
Ans: magma

2. a raised surface of the Earth through which magma flows ________
Ans: volcano

3. a type of rock which is so light that it floats on water ________
Ans: pumice

4. precious minerals mostly used for making expensive ornaments ________
Ans: gemstones

5. the process of taking out ores from the Earth ________
Ans: mining

II. Tick (✔) the correct options.

1. What is an igneous rock?
(a) A rock that is formed when lava cools.
(b) A rock formed from existing rocks.
(c) A rock formed from sediments.
(d) A rock formed in the sea.
Ans: (a)

2. Where are metamorphic rocks formed?
(a) on the surface of the Earth
(b) deep inside the Earth
(c) on the ocean floor
(d) on magma
Ans: (b)

3. Which of these sentences is not true for minerals?
(a) They are natural substances.
(b) All minerals are gemstones.
(c) They are composed of crystals.
(d) They are found in solid form.
Ans: (b)

4. What is an ore?
(a) a rock with precious stones
(b) a rock with metals
(c) a mineral
(d) a stone
Ans: (b)

5. Which of these is not true for gemstones?
(a) They are minerals.
(b) They are precious.
(c) They are part of the rocks.
(d) They are rocks formed of plant remains.
Ans: (d)

III. Tick (✔) the true sentences and correct the false ones. 

1. Magma that flows out on to the surface of the Earth is called lava.
Ans: True 

2. Basalt is formed deep below the Earth when lava flows.
Ans: False
Basalt is formed on the surface of the Earth during volcanic eruptions.

3. Sedimentary rocks are formed from lava.
Ans: False
Sedimentary rocks are formed from rock fragments and particles that settle at the bottom of seas and rivers.

4. Limestone is a kind of sedimentary rock.
Ans: True 

5. Metal ores are obtained from the Earth.
Ans: True 

6. All rocks are made up of minera.
Ans: False
Some rocks, like pumice, can be made up of volcanic glass and not minerals.

IV. Answer the following questions in one sentence. 

1. Name the three types of rocks.
Ans: Igneous, sedimentary, and metamorphic rocks.

2. What causes a volcanic eruption?
Ans: The rise of hot magma from deep below the Earth's surface.

3. What happens when magma cools much below the surface of the Earth?
Ans: It forms igneous rocks deep below the Earth.

4. What does the soil around us contain?
Ans: The soil contains broken rock fragments, minerals, and organic matter.

5. Why is pumice porous?
Ans: Pumice is porous because gases get trapped in the lava during its formation.

V. Answer the following questions In detail. 

1. Draw a labelled diagram to explain the formation of igneous rocks.
Ans:

The process of volcanic eruption, magma becoming lava, and cooling to form igneous rocks like pumice and basalt.

2. Explain how sedimentary rocks are formed.
Ans: Sedimentary rocks are formed when rocks are broken into tiny pieces by natural forces like wind and water. These rock fragments are carried by rivers into the sea, where they settle at the bottom, forming layers of sediments. Over time, the weight of upper layers compresses and hardens the sediments into rocks like sandstone, conglomerate, limestone, and shale.

3. How are metamorphic rocks formed?
Ans: Metamorphic rocks are formed when existing igneous or sedimentary rocks are subjected to heat and pressure deep within the Earth. This process, which takes millions of years, causes the rocks to change their structure and composition, resulting in metamorphic rocks like quartz and marble.

4. Explain what a mineral is.
Ans: A mineral is a natural substance found in solid form either on or below the Earth's surface. It has a definite crystalline structure and can be composed of various elements. For example, pyrite mineral forms perfect cubes.

5. Write one use for each of the following rocks:

• granite 
• basalt 
• limestone 
• shale

Ans: 

• Granite: Used in the construction of buildings and monuments.
• Basalt: Mainly used for construction purposes.
• Limestone: Used for making cement and glass; chalk, a type of limestone, is used for writing on blackboards.
• Shale: Used for making tiles and roofs.

Think and answer

I. Read the given passage and answer the questions.

The Mohs' scale is about the hardness of minerals. It was developed by Friedrich Mohs in 1812. The hardness of minerals on this scale is numbered from 1-10. Diamond is the hardest, while talc is the softest mineral. Calcite occupies the third spot and quartz is in the seventh place. 

1. Which mineral occupies the first spot?
Ans: Diamond.

2. Which is harder—calcite or talc?
Ans: Calcite.

3. A harder mineral leaves a scratch mark on a softer mineral. Will quartz leave a mark on a diamond if scratched?
Ans: No, quartz will not leave a scratch mark on a diamond as diamond is harder than quartz.

II. The Taj Mahal is one of the wonders of the world. However, over the years, the Taj Mahal has been turning yellow. The government has banned motor vehicles within two kilometres of the monument. How do you think this step will protect the Taj Mahal?
Ans: Banning motor vehicles within two kilometres of the Taj Mahal can help reduce air pollution and the deposition of pollutants on the monument's surface, preventing further discoloration and damage to the Taj Mahal.