Samacheer Kalvi 7th Science Term 3 Solutions Chapter 2 Pdf

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 2 Pdf

Tamilnadu Board Samacheer Kalvi 7th Science Term 3 Solutions Chapter 2: Tamilnadu State Board Solution Class 7 Science Term 3 Chapter 2 – Universe and Space.

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 2: Overview


Samacheer Kalvi





Chapter Name

Universe and Space

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 2 Pdf

I.) Choose the correct answers

1.) The moon takes ___ days to complete one revolution around the Earth.

a.) 25

b.) 26

c.) 27

d.) 28

Answer : c. 27

Solution : The moon takes 27 days to rotate on its axis and make one revolution around the Earth. This period of time is also called the sidereal month.


2.) If the Moon is appeaing in the sky today near the star Karthikai , the position of the Mon after 27 days is near the star

a.) Bharani

b.) Karthikai

c.) Rohini

d.) Asvini

Answer : d. Asvini

Solution : It takes 27 days for moon to complete one revolution around the Earth so keeping this in mind if the moon was near the star karthikai 27 days ago then now it’s position would be near the star Asvini.

3.) Telescope was invented by

a.) Han Lippershey

b) Galilio

c) Nicolus Coppernicus

d) Ptolomy

Answer : a. Han Lippershey

Soution :A Dutch eyeglass maker named Han Lippershey was the first person to invent a device called telescope that could magnify objects three times.

4.) The galaxy containing young and hot stars is

a.) elliptical galaxy

 b.) irregular galaxy

c.) cluster

d.) spiral galaxy

Answer : d. spiral galaxy

Solution :Spiral galaxies are made of hot young stars with beautiful shapes. They are twisted collections of stars and gases.

5.) With the launch of this satellite, ISRO became capable of launching 4 ton heavy satellites.

a.) GSAT- 13

b.) GSAT- 14

c.) GSAT- 17

 d.) Way par GSAT- 19

Answer : d. Way par GSAT- 19

Solution: ISRO became capable of launching 4 ton heavy satellites with the launch of way par GSAT-19.

II.) Fill in the blanks.

1.) Waxing of moon means __growing or expanding ___

2.) Heliocentric model is proposed by __Nicolus Copernicus ___

3.) _The Big Bang Theory ____ is the prevailing model of Evolution of the Universe

4.) __Ursa Major ___ is a large constellation which covers a large part of the sky.

5.) _Aryabhatta __ is the first satellite launched by India.


III) True or False – If False give the correct answer

1.) On a full moon day, when the Sun is setting in the west, moon rises in the West.

Answer : False

Correct Statement : On a full Moon day, when the Sun is setting in the west, Moon rises in the East

2.) The word crescent refers to the phases where the moon is less than half illuminated.

Answer : True

3.) Galilio accepted the Geo-centric model.

Answer : False

Correct Statement : Galilio did not accepted the Geo-centric model.

4.) Our Milky Way galaxy is identified as an elliptical galaxy.

Answer : False

Correct Statement : Our Milky Way galaxy is identified as an spiral galaxy.

5.) The planet Venus in our solar system doesn’t have a moon.

Answer : True

IV) Match the following

1.) Rohini – SLV-3

2.) GSAT-14 – GSLV-D5

3.) GSAT-19 – GSLV Mark III DI

4.) Chandrayaan-2 – GSLV-Mark III

5.) Mangalyaan – PSLV-XL C25

V) Analogy

1.) Older stars : elliptical galaxies :: younger stars :—-Irregular galaxies —-

2.) Nearest galaxy : Andromeda :: Nearest star :——–Alpha centauri ——-.


VI) Very short answer

The word ————— refers to the phases where the moon is less than half illuminated (cresent / gibbous)

Answer : cresent

2.) ————— and ————— planets never appear in the mid-night sky.

Answer : Mercury,  venus

3.) Number of days taken by the Mars to orbit around the Sun.

Answer : 687 days

4.) In which phase does the size of the planet Venus is small?

Answer : Gibbous phase

5.) The only evidence of the big bang theory is

Answer : The only evidence of the big bang theory is a faint glow in space, called cosmic microwave background.

6.) The galaxy which contains abundant amount of gas and dust is ___

Answer : Spiral galaxy

7.) Which country launched the world’s first artificial launch vehicle?

Answer : Russia

VII) Short Answer Questions

1.) What is epicyclic model?

Answer : Epicycle model refers to a change in simple geocentric model that early astronomers proposed to explain such puzzling phenomena.

According to Ptolemic astronomy it is a small circle whose centre is on the circumference of a larger circle. Given a fixed central earth it was taken as the basis of revolution of the seven planets.

2.) Name the four different types of galaxies.

Answer :

Four different types of galaxies are:

1) Elliptical galaxy

2) Spiral galaxy

3) Irregular galaxy

4) Barred spiral galaxy

3.) What is constellation?

Answer : A constellation is a recognizable pattern of stars in the night sky when viewed from the Earth.

4.) Give the expansions of PSLV and GSLV

Answer : PSLV: Polar Satellite Launch Vehicle.

GSLV: Geosynchronous Satellite Launch Vehicle.

VIII) Answer in Detail

1.) Explain the waxing and waning phases in Venus.

Answer :

The above diagram shows how Venus would exhibit phases when went around the Epicycle. The apparent size would grow bigger when the planet would be nearer but when it is far the apparent size would be smaller. Also The Venus would appear near the sun in the sky if it was going around the Sun and it’s orbit is inside that of Earth.

Venus would be brighter and bigger when it is near the earth compared to when it is on the other side of the Sun.

The Venus can exhibit gibbous phase only when it is revolving around the Sun. The size of the gibbous phase smaller than the crescent phase. If the Venus was revolving around the Earth, we can never see the gibbous phase of the Venus and it would be seen as if the Venus is only orbiting the Sun.

2.) Write short notes on constellations.

Answer : At night when viewed from the Earth, a pattern of stars that is recognizable in the sky is what is called as Constellation. To cover the entire celestial sphere 88 constellations has been classified by the International Astronomical Union. Many of the old constellations have Greek or Latin names , these are named after mythological characters. Ursa Major (Saptha Rishi Mandalam) is a large constellation that covers a large part of the sky.

IX.) HOT Question

Neelan and Mala are having a conversation about our Universe. Neelan is telling our earth will be the only planet in the entire Universe to have a life with. But, Mala is opposing his view by citing certain points. What would be the argument of Mala. Do you support Mala? Justify your stand.

Answer : I don’t support mala because Oxygen, water and various other gases play a vital role on Earth. It is due to the presence of these that enable us to survive on Earth and as we already know no other planet have these. So Neelan is right.

Updated: July 6, 2022 — 12:21 am

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