Class 8 Science

Stars and Solar System

Extra Questions

Short Answer Type

Question 1: Write a short note on Pole Star.

Answer: While other stars appear to move with gradual progress of night, the pole star remains fixed at its position. This happens because the pole star is in line with the axis of the earth. The pole star appears in the northern sky. It is only visible from the northern hemisphere. However, the fixed position of the pole star has helped humans since ages.

Question 2: Write a short note on Ursa Major.

Answer: It resembles the shape of a ladle. The four stars which appear as four vertices of a quadrilateral make the bowl of the ladle and the remaining three stars make the handle of the ladle. Ursa Major appears in the northern sky. The pole star is in line with last two stars of the quadrilateral. Since this constellation appears quite close to the pole star, it looks as if revolving around the pole star.

Question 3: Write a short note on Solar System.

Answer: The solar system is made up of the sun, its planets, satellites, asteroids, comets, dwarf planets, etc. All other members of the solar system keep on revolving around the sun. This is possible because of the gravitational attraction between the sun and these bodies. The solar system is 4.6 billion years old.

Question 4: What are asteroids?

Answer: The asteroid belt is present between the orbits of Mars and Jupiter. This belt extends between 2.3 and 3.3 AU from the sun. Asteroids are made up of rocks, metallic minerals and some ice. They are remnants of formation of the solar system.

Question 5: What are meteors and meteorites?

Answer: When a small object from the space reaches the atmosphere of the earth, it enters at a very high speed. The high speed creates so much friction that the object burns off before reaching the earth. Such objects are called meteors. They are visible as shooting stars in the night sky. Sometimes, an object can be too big to be completely destroyed by burning. Such objects reach the surface of the earth and are called meteorites. A meteorite can cause huge damage to the earth; like destroying a huge population of living beings.

Question 6: Write some uses of artificial satellites.

Answer: Uses of Artificial Satellites:

  • Remote sensing to collect data about minerals, cities, forests, etc.
  • Collecting data about atmosphere which can be utilized for weather prediction.
  • Transmission of signals for telecommunication and television.

Question 7: Write a short note on Mercury.

Answer: Mercury is the smallest planet in the solar system and is nearest to the sun. It is at a distance of 0.4 AU from the sun. This is so close to the sun that it cannot be seen without a powerful telescope.

Question 8: Why is the Venus called the morning and evening star?

Answer: After moon; Venus is the brightest object in the night sky. Venus is visible in early evening during the summer months and in early morning during winters. Due to this, Venus is also called the morning and evening star.

Question 9: What do you understand by phases of moon? What is the reason for different phases of moon?

Answer: The moon does not appear similar on different days rather its shape changes every day. The different shapes of the moon are called the phases of moon.

Reason of Phases of Moon: The moon takes same time in completing a revolution and a rotation. Due to this, only one surface of the moon is visible from the earth. The surface which is visible from the earth gets varying ratios of light and shadow. Due to this, we are able to see different phases of moon.

Question 10: Explain some salient features of the Earth.

Answer: Earth is the only planet where life is known to exist. According to scientists, earth is at a perfect distance from the sun and hence it has the right combination of gases, materials and temperature to support life. A major portion of the earth’s surface is covered with water and hence it appears blue from the space. Due to this; earth is also called the BLUE PLANET.

Earth’s orbital plane is tilted at 23.5° on its equatorial plane. This means that earth's axis is tilted at 66.5° on its orbital plane. Seasons change on earth because of this tilt.


Crop Production

The science of farming is called agriculture. Farming includes cultivation of plants and rearing of animals for food and other beneficial items.

Microorganisms: Friend or Foe

An organism which cannot be seen by naked eyes is called microorganism or microbe. We need a microscope to see a microbe.

Synthetic Fibres

ibres which are man-made are called synthetic fibres, e.g. nylon, acrylic, etc. A synthetic fibre is made of multiple units of a chemical substance.

Metals Non-metals

Metals are lustrous, sonorous, ductile, and are good conductor of heat and electricity.

Coal & Petroleum

Resources which from nature are called natural resources. Examples: coal, petroleum, air, water, soil, etc.

Combustion & Flame

Combustion is a chemical process in which a substance reacts with oxygen to give off heat. Some substances may also give light along with heat during combustion.

Conservation of Plants and Animals

The part of the earth where all living organisms are present is called biosphere. Biosphere is the narrow zone between hydrosphere, troposphere and atmosphere.

Cell: The Fundamental Unit of Life

The basic structural unit of a living organism is called cell. All living beings are made up of cells.

Reproduction in Animals

The process by which an organism produces its offspring is called reproduction. Reproduction is necessary to continue the lineage of an organism.

Reaching the Age of Adolescence

Adolescence is the period of life when many changes take place in the body, leading to reproductive maturity. Adolescence begins at around 10 years of age and lasts till 18 or 19 years of age.

Force & Pressure

A push or pull on an object is called force. Pressure is the force acting on a unit area on an object.

Friction

When one surface is moving over another surface, a force comes into play and opposes their relative motion. This force is called friction or force of friction.

Sound

Sound is a kind of wave which gives us the sense of hearing. Sound is produced by a vibrating body.

Chemical Effects of Electric Current

When electric current is passed through a conducing solution, some chemical reaction takes place in the solution. This is called chemical effect of electric current.

Natural Phenomena

Transfer of charge from one object to another is called charging. The process of transfer of charge to the earth is called earthing.

Light

When light falls on a shiny surface, most of it bounces back. This phenomenon is called reflection of light.

Solar System

The solar system is made up of the sun, its planets, satellites, asteroids, comets, dwarf planets, etc. All other members of the solar system keep on revolving around the sun.

Pollution

When air is contaminated with unwanted substances and becomes harmful for the living and non-living, this is called air pollution.