Class 8 Unit-11 (The Earth & Space)

 

Unit-11

The Earth & Space

 

Exercise

 

Very Short Questions:

1.   Define metallic minerals.
➤ Minerals that contain metals and can be melted to get metal.

2.   Define nonmetallic minerals.
➤ Minerals that do not contain metals and cannot be melted.

3.   What type of minerals are good conductors of heat and electricity?
➤ Metallic minerals.

4.   Is the quartz metallic or nonmetallic?
➤ Nonmetallic.

5.   Where is the iron mine found in Nepal?
➤ Phulchoki, Lalitpur.

6.   What are the uses of copper?
➤ Making wires, coins, and utensils.

7.   From which mineral is pencil made?
➤ Graphite.

Short Questions:

1.   Define minerals with two examples.
➤ Naturally occurring substances found in the earth.
➤ Examples: Iron, Mica.

2.   Give three examples of nonmetallic minerals.
➤ Mica, Quartz, Sulphur.

3.   What are the uses of Iron?
➤ Making tools, machines, and buildings.

4.   Where does the mine of lead find in Nepal?
➤ Ganesh Himal and Baglung.

5.   What are the important characteristics of minerals?
➤ Naturally occurring, solid, inorganic, and have a definite chemical structure.

Give Reason:

1.   Most of the rocks are formed long ago.
➤ Because it takes millions of years for rocks to form under the earth.

2.   Iron is mostly used in Nepal.
➤ Because it is strong, durable, and useful in making tools and buildings.

 

Differentiate Between:

a. Metallic minerals and nonmetallic minerals

Metallic Minerals

Nonmetallic Minerals

Contain metals

Do not contain metals

Good conductors of electricity

Poor conductors

Can be melted to get metal

Cannot be melted

Example: Iron, Copper

Example: Mica, Quartz

 

b. Chalcopyrite and Hematite

Chalcopyrite

Hematite

Ore of Copper

Ore of Iron

Yellow in color

Reddish-brown in color

 

 

 

 

 

c. Zinc and Copper

Zinc

Copper

Bluish-white metal

Reddish-brown metal

Used in galvanizing

Used in wires and coins

 

 

Long questions

1. What are minerals? Give some examples. Explain the uses of minerals.

Answer:
Minerals are natural substances found in the earth. They are solid, non-living, and have a definite chemical structure.

Examples:

  • Iron
  • Copper
  • Mica

Uses of minerals:

  • Iron is used to make tools and machines.
  • Copper is used to make electric wires and coins.
  • Mica is used in electrical equipment.

2. Name some important minerals found in Nepal. Mention the places where they are found.

Answer:
Here are some important minerals found in Nepal with their places:

Mineral

Place

Iron

Phulchoki, Lalitpur

Limestone

Udayapur, Chovar

Slate

Argakhanchi

Lead

Ganesh Himal

Copper

Gyaji, Gulmi

Mica

Bajhang

3. What are ores of iron and copper? What are the characteristics of minerals? Explain the uses of graphite.

Answer:

  • Ore of Iron: Hematite
  • Ore of Copper: Chalcopyrite

Characteristics of minerals:

  • Found naturally
  • Solid in form
  • Have definite chemical structure
  • Inorganic in nature

Uses of Graphite:

  • Used to make pencil lead
  • Used as a lubricant
  • Used in batteries and brushes of motors

4. What are the uses of minerals?

Answer:

  • Used to make tools, machines, and vehicles
  • Used in construction (like cement and bricks)
  • Used in making jewelry (like gold and silver)
  • Used in electrical equipment (like copper wire, mica)
  • Used in agriculture (as fertilizers)

 

 

 

Next exercise

Very short answer questions

1. Which hypothesis explains the origin of the earth by the togetherness of dust particles?

➤ Nebular Hypothesis

2. Which is the first eon?

➤ Hadean Eon

3. Which eon is divided into three eras?

➤ Phanerozoic Eon

4. In which era, the society was dominated with dinosaurs?
→ Dinosaurs dominated during the Mesozoic era.

5. When was the Homo sapiens evolved?
→ Homo sapiens (modern humans) evolved about 200,000 years ago in the Cenozoic era.

6. What can be the ancestor of all living creatures?
→ The single-celled organism or unicellular organism is considered the ancestor of all living creatures.

7. What is the possible time range of Paleozoic era?
→ The Paleozoic era lasted from about 541 million to 252 million years ago.

 

 

Short Questions with Answers

1. When did mammoths with long tusks and fish with lungs evolve?
→ Mammoths evolved in the Cenozoic era and fish with lungs evolved in the Devonian period of the Paleozoic era.

2. What types of organisms originated in Cryptozoic eon?
→ Simple organisms like bacteria and algae originated in the Cryptozoic eon.

3. Name the era in the following organisms to be evolved:

  • Human – Cenozoic era
  • Tree-fern – Paleozoic era
  • Entelodon wild boar – Cenozoic era
  • Algae – Cryptozoic eon
  • Dinosaur – Mesozoic era
  • Monkey – Cenozoic era
  • Frog – Paleozoic era
  • Monocot plant – Mesozoic era
  • Coniferous plant – Mesozoic era
  • Bacteria – Cryptozoic eon
  • Mosquito – Cenozoic era
  • Trilobites – Paleozoic era
  • Jellyfish – Cryptozoic eon
  • Toothed bird – Mesozoic era

4. Was there oxygen in the beginning of life development?
→ No, there was no oxygen in the beginning of life development.

Give Reason

a. Human civilization started after millions of years after the origin of the solar system.
→ Because the Earth took millions of years to become suitable for life and the development of humans took even longer.

b. Life was not possible during the beginning of our home planet, the earth.
→ Because Earth was extremely hot, unstable, and lacked oxygen and water.

c. All lives should have the single common ancestor.
→ Because all living things share similar genetic materials and basic cell structures.

d. Mesozoic era is called era of Creepers.
→ Because reptiles like dinosaurs, which crawl or creep, dominated during this era.

e. The Cenozoic era is the most modern era.
→ Because humans and other modern animals evolved in this era.

Differentiate Between

a. Palaeozoic era and Cenozoic era:

  • Palaeozoic era: Ancient life like trilobites and fishes.
  • Cenozoic era: Modern life like mammals and humans.

b. Cryptozoic eon and Phanerozoic eon:

  • Cryptozoic eon: Hidden life; simple organisms like bacteria.
  • Phanerozoic eon: Visible life; complex organisms like animals and humans.

c. Nebular hypothesis and Planetesimal hypothesis:

  • Nebular hypothesis: Earth and planets formed from a rotating gas cloud.
  • Planetesimal hypothesis: Earth formed by joining of small solid particles.

d. Era of reptiles and Era of mammals:

  • Era of reptiles: Mesozoic era, when dinosaurs were dominant.
  • Era of mammals: Cenozoic era, when mammals and humans evolved.

 

 

Next exercise

B. Very Short Questions – Easy Answers

1. Which theory is believed as the origin of universe?
→ Big Bang Theory is believed to be the origin of the universe.

2. What are the major constituents of solar system?
→ The Sun, planets, moons, asteroids, and comets.

3. What may be the shape of Milky Way?
→ The Milky Way is spiral-shaped.

4. What is the diameter of Milky Way?
→ About 1,00,000 light years.

5. What are asteroids?
→ Asteroids are rocky objects that orbit the Sun, mostly found between Mars and Jupiter.

6. Why asteroids are also called minor planets?
→ Because they resemble small planets and orbit the Sun.

7. What is the value of 1 light year in metre?
→ 1 light year = 9.46 × 10¹⁵ metres

8. What is meteor shower?
→ A meteor shower is when many meteors fall from the sky in a short time.

9. In which galaxy our home planet lies?
→ Earth lies in the Milky Way galaxy.

10. Which is the largest constellation?
→ Hydra is the largest constellation.

C. Short Questions

1. What does Big Bang theory explain?
→ It explains that the universe began with a huge explosion about 13.8 billion years ago and is still expanding.

2. How is constellation formed?
→ Constellations are formed by groups of stars that appear to form patterns in the sky.

3. What are comets? From where the comets revolve the sun?
→ Comets are ice and dust objects that revolve around the Sun.
They come from the Kuiper Belt and Oort Cloud.

4. Which three scientists explain about the expansion of universe?
→ Edwin Hubble, Albert Einstein, and Stephen Hawking.

5. What is singularity? How does Stephen Hawking explain the singularity?
→ Singularity is a point with infinite density and gravity.
Stephen Hawking said the universe started from a singularity.

6. In which time range the universe expanded in most speed?
→ During the Inflation period, just after the Big Bang.

7. What are meteorites means? How they form?
→ Meteorites are pieces of meteors that reach Earth’s surface.
They form when meteors survive burning in the atmosphere.

8. What are the name of twelve zodiac?
→ Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces

 

9. Give Reason – Easy Answers

a. The distance of stars is measured in light year.
→ Because stars are very far away, and using kilometers or miles would be too big to handle.
So, we use light year, which is the distance light travels in one year.

b. Large meteorites occasionally fall on the earth.
→ Because sometimes big meteors do not completely burn in Earth’s atmosphere and fall as meteorites on the surface.

c. Big Bang is the most accepted theory on origin of universe.
→ Because it explains well how the universe started from a single explosion, and scientific evidence like redshift and cosmic background radiation support it.

 

Differentiate between

a. Stars and planets

  • Stars: Give their own light and heat (e.g., Sun).
  • Planets: Do not have their own light; they reflect sunlight (e.g., Earth).

b. Meteorites and meteoroids

  • Meteoroids: Small rocks or particles moving in space.
  • Meteorites: When meteoroids enter Earth's atmosphere and fall to the ground.

c. Main asteroid belt and Kuiper belt

  • Main asteroid belt: Found between Mars and Jupiter.
  • Kuiper belt: Beyond Neptune, contains icy bodies and dwarf planets.

d. Dust tail and iron tail

  • Dust tail: Made of dust particles, appears white.
  • Iron (ion) tail: Made of gases, appears bluish and always points away from Sun.

e. Endocomet and exocomet

  • Endocomet: A comet inside our solar system.
  • Exocomet: A comet outside our solar system (in other star systems).

Long questions

1. What is universe? Explain the constituents of the universe.

The universe is everything that exists, including all stars, planets, galaxies, and space.
Constituents:

  • Stars
  • Planets
  • Satellites
  • Asteroids
  • Comets
  • Meteoroids
  • Gas and dust

2. Explain the theory that gives the concept on origin of universe.

Big Bang theory:
It says the universe started about 13.8 billion years ago from a very tiny, hot, and dense point. It suddenly expanded and is still expanding today.

3. Discuss about meteoroids, meteors, and meteorites.

  • Meteoroids: Rocks or metal pieces moving in space.
  • Meteors: When meteoroids enter Earth’s atmosphere, they burn and make a bright light (shooting stars).
  • Meteorites: When meteors do not completely burn and fall to Earth.

4. Describe the formation and disappearance of tail of comet.

When a comet comes near the Sun, its ice melts and dust/gas come out, forming a tail.
When it goes far from the Sun, it becomes cold again and the tail disappears.

5. What are asteroids? How and where they lie during the revolution of the earth?

Asteroids are small rocky objects.
They mainly lie in the asteroid belt between Mars and Jupiter. They move around the Sun, like planets.

6. What are the parts of comet? Draw a figure of comet and label them.

Parts:

  • Nucleus (center part, solid)
  • Coma (cloud of gas and dust around nucleus)
  • Dust tail
  • Ion tail

Figure of comet

 

 

 


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