Samacheer Kalvi Class 6 Social Science Solutions Term 1 Chapter 1 The Universe and Solar System

Tamilnadu Samacheer Kalvi 6th Social Science Geography Solutions Term 1 Chapter 1 The Universe And Solar System

Samacheer Kalvi 6th Social Science The Universe And Solar System Text Book Back Questions And Answers

A. Fill In The Blanks

Question 1. The Universe was formed after explosion.
Answer: The Universe was formed after **Big Bang** explosion. The universe began with this huge event, where all matter and energy exploded outwards from a very hot, dense state. This event led to everything we see today.
In simple words: The Big Bang is the name for the huge explosion that started the universe.

🎯 Exam Tip: Remember to capitalize "Big Bang" as it refers to a specific scientific theory.

Question 2. is the unit used to measure the distance between two celestial bodies.
Answer: **Light year** is the unit used to measure the distance between two celestial bodies. It measures the distance light travels in one year, which is incredibly far. This unit helps astronomers describe vast cosmic distances.
In simple words: A light-year is how far light travels in one year, used to measure huge distances in space.

🎯 Exam Tip: Be careful not to confuse "light-year" with a unit of time; it's always a measure of distance.

Question 3. is the centre of the solar system.
Answer: **The Sun** is the centre of the solar system. All the planets and other celestial bodies revolve around it. The Sun's gravity holds our entire solar system together.
In simple words: The Sun is the middle of our solar system, and everything else goes around it.

🎯 Exam Tip: Mentioning that planets revolve around the Sun due to its gravity adds scientific accuracy to your answer.

Question 4. The word planet means
Answer: The word planet means **wanderer**. This name was given because, unlike stars, planets move across the sky over time. Ancient observers noticed their changing positions against the background of fixed stars.
In simple words: The word 'planet' means 'wanderer' because planets move across the sky.

🎯 Exam Tip: Knowing the etymology of scientific terms can sometimes help remember their meaning and context.

Question 5. planet has many natural satellites.
Answer: **Jupiter** planet has many natural satellites. It is the largest planet in our solar system and has a vast family of moons orbiting it. Many of these moons are quite large themselves.
In simple words: Jupiter has a lot of natural moons, more than any other planet.

🎯 Exam Tip: Remember that "natural satellites" refers to moons, and gas giants like Jupiter typically have many.

Question 6. India's first ever mission to the moon is
Answer: India's first ever mission to the moon is **Chandrayaan**. This mission was launched to explore the Moon's surface and gather scientific data. It marked a significant achievement for India's space program.
In simple words: Chandrayaan was the name of India's first trip to the moon.

🎯 Exam Tip: For space missions, it's important to know the name of the mission and the celestial body it explored.

Question 7. Earth is inclined by degrees.
Answer: Earth is inclined by \( 23\frac { 1 }{ 2 } \) degrees. This tilt in Earth's axis causes the different seasons we experience throughout the year. The angle of sunlight changes as Earth orbits the Sun.
In simple words: The Earth is tilted at \( 23\frac { 1 }{ 2 } \) degrees, and this tilt causes the seasons.

🎯 Exam Tip: Understanding Earth's axial tilt is key to explaining why we have seasons.

Question 8. The Equator faces the Sun directly on
Answer: The Equator faces the Sun directly on **21st March, 23rd September**. These two dates are known as the equinoxes, when day and night are almost equal in length all over the world. During these times, the sun is directly overhead at the equator.
In simple words: The Equator gets direct sunlight on March 21st and September 23rd, making day and night equal.

🎯 Exam Tip: Remember the dates of the equinoxes as they are important for understanding Earth's seasons and daylight patterns.

Question 9. At the time of Perihelion, the Earth is
Answer: At the time of Perihelion, the Earth is **Closest**. Perihelion is the point in Earth's orbit when it is nearest to the Sun. This event typically occurs in early January each year.
In simple words: Perihelion is when the Earth is closest to the Sun in its orbit.

🎯 Exam Tip: Distinguish between perihelion (closest to Sun) and aphelion (farthest from Sun) for full marks.

Question 10. The line which divides day and night on the Earth's surface is
Answer: The line which divides day and night on the Earth's surface is **Terminator line**. This imaginary line constantly moves as the Earth rotates, creating the cycle of sunrise and sunset. It marks the boundary between the illuminated and dark halves of the Earth.
In simple words: The terminator line is the edge that separates the day side of Earth from the night side.

🎯 Exam Tip: Visualizing the terminator line helps understand why different parts of the Earth experience day and night at various times.

B. Choose The Best Answer

Question 1. The movement of the Earth on its axis is called
(a) Revolution
(b) Seasons
(c) Rotation
(d) Circulation
Answer: (c) Rotation
In simple words: When the Earth spins around itself, like a top, it's called rotation. This spinning causes day and night.

🎯 Exam Tip: Remember that rotation causes day and night, while revolution (Earth orbiting the Sun) causes seasons.

Question 2. The Tropic of Capricorn faces the Sun directly on
(a) March 21
(b) June 21
(c) September 23
(d) December 22
Answer: (d) December 22
In simple words: The Tropic of Capricorn gets direct sunlight on December 22nd. This day marks the start of summer in the southern parts of the world.

🎯 Exam Tip: Note the dates for direct sunlight on the Tropics of Cancer and Capricorn, as well as the Equator, to answer such questions accurately.

Question 3. The galaxy in which our solar system is found is
(a) Andromeda
(b) Magellanic clouds
(c) Milky way
(d) Starburst
Answer: (c) Milky way
In simple words: Our solar system, including Earth, is located inside the Milky Way galaxy. It's a huge spiral-shaped galaxy.

🎯 Exam Tip: Always remember the name of our home galaxy, the Milky Way.

Question 4. The only celestial body where man has successfully landed
(a) Mars
(b) Moon
(c) Mercury
(d) Venus
Answer: (b) Moon
In simple words: Humans have only landed on the Moon so far. The Apollo missions successfully sent astronauts there many years ago.

🎯 Exam Tip: This is a factual question; recall the historic Apollo missions and their destination.

Question 5. Which of the following planets can float On water?
(a) Jupiter
(b) Saturn
(c) Uranus
(d) Neptune
Answer: (b) Saturn
In simple words: Saturn is made mostly of light gases, so it is less dense than water. This means it could float if placed in a large enough body of water.

🎯 Exam Tip: Remember Saturn's low density due to its gaseous composition as a key characteristic.

C. Circle The Odd One Out

Question 1. Venus, Jupiter, Neptune, Saturn
Answer: Venus
In simple words: Venus is a rocky inner planet, while Jupiter, Neptune, and Saturn are all large, gaseous outer planets.

🎯 Exam Tip: Classify planets into inner (terrestrial, rocky) and outer (Jovian, gaseous) to easily spot the odd one out.

Question 2. Sirus, Andromeda, Milky way, Magellanic clouds.
Answer: Sirus
In simple words: Sirius is a single star, but Andromeda, Milky Way, and Magellanic clouds are all large groups of stars called galaxies.

🎯 Exam Tip: Differentiate between individual stars and larger structures like galaxies when identifying celestial objects.

Question 3. Pluto, Eris, Ceres, Io
Answer: Io
In simple words: Io is a moon that orbits Jupiter, while Pluto, Eris, and Ceres are all dwarf planets that orbit the Sun.

🎯 Exam Tip: Remember that moons are natural satellites of planets, whereas dwarf planets orbit the Sun directly.

Question 4. Comet, Asteroids, Meteorites, Dwarf planets
Answer: Dwarf planets
In simple words: Comets, asteroids, and meteorites are usually smaller space rocks or icy bodies, while dwarf planets are larger, round celestial bodies.

🎯 Exam Tip: Group celestial objects by their size and definition; dwarf planets have a distinct classification from smaller debris.

Question 5. Rover, Orbiter, Aeroplane, Space shuttle
Answer: Aeroplane
In simple words: An aeroplane flies in Earth's air, but a rover, orbiter, and space shuttle are all used to travel or explore in space.

🎯 Exam Tip: Distinguish between vehicles designed for atmospheric flight and those designed for space exploration.

D. Match The Following

Question. Match the following

🎯 Exam Tip: Learn the unique characteristics of each planet to quickly make these associations.

E. (I) Consider The Following Statements

Question. Choose the correct answer using the codes given below.
1. Venus rotates from east to west.
2. The Tropic of Cancer faces the Sun on June 21.
3. Mars has rings around it.
(a) 1 and 2
(b) 2 and 3
(c) 1, 2 and 3
(d) 2 only
Answer: (a) 1 and 2
In simple words: Venus spins backward, and the Tropic of Cancer gets direct sun on June 21st. Mars does not have rings.

🎯 Exam Tip: Remember specific planetary facts like Venus's retrograde rotation and the solstices' dates for the Tropics.

E. (Ii) Consider The Following Statements

Question. Which of the statement(s) is/are true?
Statement I: Earth is called a watery planet.
Statement II: The rotation of the Earth causes seasons.
(a) I is true; II is wrong
(b) I is wrong; II is true
(c) Both the statements are true
(d) Statements I and II are wrong.
Answer: (a) I is true; II is wrong
In simple words: Earth is called a watery planet because it has so much water. But seasons are caused by Earth moving around the Sun and its tilt, not by it spinning.

🎯 Exam Tip: Clearly differentiate between the effects of Earth's rotation (day/night) and revolution (seasons).

F. Name The Following

Question 1. Cluster of stars.
Answer: A cluster of stars is called a **Galaxy**. Our solar system is part of the Milky Way galaxy. Galaxies are vast collections of stars, gas, and dust.
In simple words: Many stars grouped together are called a galaxy.

🎯 Exam Tip: Remember that a galaxy is a fundamental unit of stars in the universe.

Question 2. The nearest galaxy to the solar system.
Answer: The nearest galaxy to the solar system is **Andromeda**. It is a large spiral galaxy similar to the Milky Way, and it is slowly moving towards us. Scientists predict it will collide with our galaxy in billions of years.
In simple words: Andromeda is the big galaxy closest to our own solar system.

🎯 Exam Tip: Andromeda is a significant galaxy to know, often visible from Earth with the naked eye under dark skies.

Question 3. The brightest planet.
Answer: The brightest planet is **Venus**. Its thick, reflective clouds make it very shiny when seen from Earth. It is often visible in the morning or evening sky.
In simple words: Venus is the brightest planet because its clouds reflect a lot of sunlight.

🎯 Exam Tip: Venus is often called the "Morning Star" or "Evening Star" due to its brightness and visibility.

Question 4. The living sphere.
Answer: The living sphere is the **Biosphere**. This is the part of Earth where all life exists, including animals, plants, and microorganisms. It covers parts of the land, water, and air.
In simple words: The biosphere is the part of Earth where living things are found.

🎯 Exam Tip: Understand the four main spheres of Earth (lithosphere, hydrosphere, atmosphere, biosphere) and their interactions.

Question 5. The year which has 366 days.
Answer: The year which has 366 days is a **Leap year**. An extra day, February 29th, is added every four years to keep our calendar aligned with Earth's orbit around the Sun. This accounts for the extra quarter day in Earth's revolution time.
In simple words: A leap year has 366 days instead of 365, with an extra day in February every four years.

🎯 Exam Tip: Remember the purpose of a leap year: to synchronize the calendar year with the astronomical year.

G. Answer In Brief

Question 1. Name the inner planets.
Answer: The inner planets are Mercury, Venus, Earth, and Mars. These planets are close to the Sun and are primarily composed of rock and metal. They are also known as terrestrial planets due to their solid surfaces.
In simple words: The inner planets are Mercury, Venus, Earth, and Mars.

🎯 Exam Tip: Knowing the order of planets from the Sun helps in identifying inner and outer planets.

Question 2. Pluto is no longer a planet, Reason out,
Answer: Pluto is no longer considered a full planet because, in August 2006, the International Astronomical Union (IAU) reclassified it as a dwarf planet. The IAU set three rules for a full-sized planet:
1. It must orbit the Sun.
2. It must be massive enough to be nearly round due to its own gravity.
3. It must have cleared its orbit of other debris and objects.
Pluto only meets the first two rules, as it shares its orbital neighborhood with other objects in the Kuiper Belt. Thus, it was downgraded to a dwarf planet. It is part of a larger population of similar small bodies in its region.
In simple words: Pluto is now called a dwarf planet because it hasn't cleared other objects from its path around the Sun, which is a rule for full planets.

🎯 Exam Tip: Focus on the three criteria defined by the IAU for a celestial body to be classified as a planet, especially the "cleared its neighborhood" rule.

Question 3. What is perihelion?
Answer: Perihelion is the Earth's closest position to the Sun. It is the point in Earth's elliptical orbit where it is nearest to the Sun. This event happens once a year, usually in early January, and makes the Earth slightly warmer on average.
In simple words: Perihelion is when the Earth is at its closest point to the Sun during its yearly journey.

🎯 Exam Tip: Remember that perihelion occurs when Earth is closest to the Sun, while aphelion is when it's farthest.

Question 4. How many times in a year would you find the Sun overhead if you lived on 20 N Latitude?
Answer: If you lived on 20 N Latitude, you would find the Sun overhead two times in a year. This would happen around the 21st March and the 23rd September. These dates correspond to the equinoxes, when the Sun's direct rays are passing over the equator as it moves between the Tropics.
In simple words: The Sun would be directly over your head twice a year at 20 degrees North latitude, around March 21st and September 23rd.

🎯 Exam Tip: Understand that the Sun is directly overhead only between the Tropics of Cancer and Capricorn, hitting any specific latitude twice a year if it's within that range.

Question 5. Which celestial body shares its orbit with others? Give an example.
Answer: The celestial bodies that share their orbits with others are **dwarf planets**. For example, the five recognized dwarf planets in our solar system are Pluto, Ceres, Eris, Makemake, and Haumea. These objects orbit the Sun but have not cleared their orbital path of other smaller bodies. They often reside in regions like the Kuiper Belt or asteroid belt.
In simple words: Dwarf planets share their orbits with other space objects. Examples include Pluto, Ceres, and Eris.

🎯 Exam Tip: The key defining characteristic of dwarf planets is that they share their orbital space with other similar-sized objects.

H. Give Reasons

Question 1. Why is Uranus called the somersaulting planet?
Answer: Uranus is called the somersaulting planet because its axis is tilted extremely far, almost parallel to its orbit. This means it appears to roll along its path around the Sun, rather than spinning upright like other planets. This unique tilt causes extreme seasons.
In simple words: Uranus is called the somersaulting planet because it spins sideways, making it look like it rolls around the Sun.

🎯 Exam Tip: The extreme axial tilt is the key reason for Uranus's nickname; mention its almost horizontal rotation.

Question 2. The surface of the moon has many craters.
Answer: The surface of the Moon has many craters because these bowl-shaped depressions are formed when meteorites and asteroids collide with its surface. Unlike Earth, the Moon has no atmosphere or geological activity to erase these impact marks over time. Therefore, they remain preserved for billions of years.
In simple words: Craters on the Moon are made by meteorites hitting its surface, and there's no wind or water to make them disappear.

🎯 Exam Tip: When explaining craters, highlight the Moon's lack of atmosphere and geological processes as reasons for their long-term preservation.

Question 3. The velocity of Earth's rotation is zero at poles. It is due to the shape and inclination of the earth.
Answer: The velocity of Earth's rotation is zero at the poles because the poles are the fixed points around which the Earth spins. As Earth is a sphere, points at the poles are just rotating on their own axis without moving laterally, unlike points at the equator that travel a large distance in one rotation. This is a direct consequence of its spherical shape and rotational motion.
In simple words: At the Earth's poles, the spinning speed is zero because they are just the pivot points of rotation, not moving around themselves.

🎯 Exam Tip: Explain that points at the poles are on the axis of rotation itself, so their linear speed is zero, unlike points at other latitudes.

I. Answer In Detail

Question 1. Distinguish between inner and outer planets.
Answer:**Inner or Terrestrial Planets**
1. These include Mercury, Venus, Earth, and Mars.
2. They are comparatively smaller in size.
3. They are primarily composed of rocks and metals, having solid surfaces with features like mountains, volcanoes, and craters.
4. None of the inner planets have rings orbiting them. These planets are denser and have fewer moons. **Outer Planets or Jovian Planets, or Gaseous Giants**
1. These include Jupiter, Saturn, Uranus, and Neptune.
2. They are generally much larger in size.
3. Most of them are made of gas, mainly hydrogen and helium, with small rocky cores.
4. All of the outer planets have rings orbiting them, though Saturn's are the most prominent. They have many moons and are less dense than inner planets.
In simple words: Inner planets are small and rocky like Earth, close to the Sun. Outer planets are large and gassy like Jupiter, far from the Sun, and all have rings.

🎯 Exam Tip: For distinctions, organize your answer into clear points for each category and highlight key differences like composition, size, and presence of rings.

Question 2. What are the effects of rotation and revolution?
Answer:The Earth's movements, rotation and revolution, have distinct effects on our planet: **Effects of Rotation:**
1. Rotation is the spinning movement of the Earth on its own axis.
2. The time it takes for the Earth to complete one rotation is approximately 24 hours, which we call a day.
3. The rotation of the Earth causes the cycle of day and night.
4. Since the Earth is spherical, only one half of it is illuminated by the Sun at any given time, experiencing day.
5. The other half remains dark, experiencing night. This constant turning creates the daily rhythm of light and darkness. **Effects of Revolution:**
1. Revolution is the movement of the Earth around the Sun along its elliptical path.
2. The Earth takes about 365 and a quarter days to complete one full revolution, defining one year.
3. It revolves around the Sun at an impressive speed of approximately 30 kilometers per second.
4. The remaining quarter day from the \( 365\frac { 1 }{ 4 } \) days is added once every four years, creating a leap year with 366 days in February.
5. The inclination of the Earth on its axis, combined with its revolution around the Sun, is what primarily causes the different seasons we experience.
In simple words: Earth's spinning (rotation) causes day and night. Earth's trip around the Sun (revolution), combined with its tilt, creates the different seasons and defines a year.

🎯 Exam Tip: Clearly separate the effects of rotation and revolution, and remember that both the axial tilt and revolution are necessary for seasons.

Question 3. Explain the characteristics of the various spheres of the Earth.
Answer:Earth is a unique planet because it supports life, largely due to its three major interconnected components, often called realms or spheres: the lithosphere, hydrosphere, and atmosphere. These form the base for the biosphere. (i) **Lithosphere:** This term comes from the Greek word "Lithos," meaning rock. The lithosphere is the solid, outermost layer of Earth, including the land we live on, mountains, and the ocean floor. It consists of the Earth's crust and the upper part of the mantle. (ii) **Hydrosphere:** Derived from the Greek word "Hydro," meaning water, the hydrosphere includes all the water on Earth. This comprises oceans, seas, rivers, lakes, groundwater, and ice caps on mountains. Water is crucial for all life and constantly moves through a global cycle. (iii) **Atmosphere:** The word "Atmo" means air in Greek. The atmosphere is the blanket of air surrounding the Earth. It is a mixture of different gases, mainly nitrogen (78%) and oxygen (21%), which are vital for breathing and protecting life from harmful solar radiation. (iv) **Biosphere:** This is the narrow zone of Earth where life exists. It is the region where the lithosphere, hydrosphere, and atmosphere interact, creating conditions suitable for living organisms. "Bio" means life in Greek, and this sphere contains diverse ecosystems. All life forms, from tiny microbes to large animals, are part of this living system.
In simple words: Earth has four main parts: the solid land (lithosphere), all the water (hydrosphere), the air (atmosphere), and the place where all living things are found (biosphere). These parts all work together to support life.

🎯 Exam Tip: Define each sphere with its Greek root and provide examples of what each sphere includes to illustrate its meaning.

J. Picture Study

Question 1. Study the picture and answer the given questions.
Answer:

(a) **Which is the closest planet to the Sun?**
**Answer:** **Mercury** is the closest planet to the Sun. It has the shortest orbital period, taking only about 88 Earth days to complete one trip around the Sun. Mercury is also the smallest planet in our solar system.
(b) **Which is the largest planet?**
**Answer:** **Jupiter** is the largest planet. It is a gas giant with a diameter more than 11 times that of Earth. Jupiter's massive size and strong gravitational pull influence other bodies in the solar system.
(c) **Which is the farthest planet from the Sun?**
**Answer:** **Neptune** is the farthest planet from the Sun. Due to its extreme distance, it is also one of the coldest planets in our solar system. It takes about 165 Earth years to complete one orbit.
(d) **Which is the second smallest planet?**
**Answer:** **Mars** is the second smallest planet. Only Mercury is smaller than Mars. Mars is known for its reddish appearance and has two small moons, Phobos and Deimos.
In simple words: The picture shows our solar system. Mercury is nearest to the Sun, Jupiter is the biggest, Neptune is the farthest away, and Mars is the second smallest.

🎯 Exam Tip: Be able to identify planets by their relative positions, sizes, and unique characteristics when studying diagrams.

Question 2. Look at the picture and answer the questions given below.
Answer:(a) **Identify the planet**
**Answer:** The planet identified in the picture is **Uranus**. It is recognized by its distinct pale blue-green color.
(b) **What is the colour of the planet?**
**Answer:** The color of the planet is **Green**. This green hue is a characteristic feature of Uranus.
(c) **Why is it of this colour?**
**Answer:** It is of this color due to the presence of **Methane** in its atmosphere. Methane gas absorbs red light and strongly reflects blue and green light, giving Uranus its characteristic appearance. This absorption makes the planet appear greenish-blue.
In simple words: The planet in the picture is Uranus. It looks green because there is methane gas in its atmosphere.

🎯 Exam Tip: Relate the color of gas giants like Uranus and Neptune to the gases in their atmospheres, especially methane.

Student Activity

K. Solve The Puzzle

Question. Solve the puzzle based on the following clues:
Across:
2. A dwarf planet.
3. Equal days and nights.
7. I am a gas found in the Sun.
8. I appear once in 76 years.
Down:
1. I am the morning star.
2. India's first moon mission.
4. I have two natural satellites.
5. I am the farthest planet.
6. An imaginary line passing through the centre of the Earth.
Answer:**Across:**
2. CERES
3. EQUINOX
7. HYDROGEN
8. HALLEY
**Down:**
1. VENUS
2. CHANDRAYAAN
4. MARS
5. NEPTUNE
6. AXIS
In simple words: The answers to the puzzle clues are: Across - CERES, EQUINOX, HYDROGEN, HALLEY. Down - VENUS, CHANDRAYAAN, MARS, AXIS.

🎯 Exam Tip: Crossword puzzles test your knowledge of definitions and facts, so a strong grasp of vocabulary and concepts is helpful.

Samacheer Kalvi 6th Social Science The Universe And Solar System Additional Important Questions And Answers

I. Fill In The Blanks

Question 1. The study of the universe is called
Answer: The study of the universe is called **Cosmology**. This field explores the origin, evolution, and large-scale structures of the cosmos. It tries to understand how everything in space came to be.
In simple words: Cosmology is the study of the entire universe, including how it started.

🎯 Exam Tip: Remember that "cosmology" specifically refers to the study of the universe as a whole, not just parts of it.

Question 2. A cluster of stars is known as
Answer: A cluster of stars is known as a **Galaxy**. Galaxies are enormous collections of stars, gas, dust, and dark matter held together by gravity. Our Sun is just one star in the Milky Way galaxy.
In simple words: A galaxy is a very large group of stars.

🎯 Exam Tip: Differentiate between a "star cluster" (smaller group of stars within a galaxy) and a "galaxy" (vast system of billions of stars).

Question 3. The Roman word 'Sol' means
Answer: The Roman word 'Sol' means **Sun God**. This is why our Sun is often referred to with terms like "solar" system, meaning "of the Sun." It reflects ancient cultures' reverence for the Sun.
In simple words: The Roman word 'Sol' means the Sun God.

🎯 Exam Tip: Connecting the word "Sol" to "solar" helps you remember its meaning and relevance to our solar system.

Question 4. The is at the centre of the solar system.
Answer: The **Sun** is at the centre of the solar system. It is a star that provides heat and light to all the planets orbiting it. Its immense gravitational pull keeps everything in its place.
In simple words: The Sun is in the middle of our solar system.

🎯 Exam Tip: Confirming the Sun's central role reinforces the heliocentric model of our solar system.

Question 5. The elliptical path in which the planets move around the Sun is
Answer: The elliptical path in which the planets move around the Sun is an **Orbit**. Each planet follows its own specific elliptical path as it continuously revolves around the Sun. These paths are precisely defined by gravitational forces.
In simple words: The curved path that planets follow around the Sun is called an orbit.

🎯 Exam Tip: Remember that planetary orbits are elliptical, not perfect circles.

II. Choose The Correct Answer

Question 1. The closest planet to the Sun is
(a) Mercury
(b) Venus
(c) Uranus
(d) Saturn
Answer: (a) Mercury
In simple words: Mercury is the closest planet to the Sun. It also travels around the Sun the fastest.

🎯 Exam Tip: Listing the planets in order from the Sun (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) helps answer questions about their positions.

Question 2. The solar system is believed to have formed about billion years ago.
(a) 3
(b) 4.5
(c) 3.5
(d) 5
Answer: (b) 4.5
In simple words: Scientists believe our solar system was created about 4.5 billion years ago from a big cloud of gas and dust.

🎯 Exam Tip: Recall the approximate age of the solar system, which is a key figure in astronomy and geology.

Question 3. The ringed planet is
(a) Mars
(b) Venus
(c) Saturn
(d) Mercury
Answer: (c) Saturn
In simple words: Saturn is known for its beautiful rings, which are made of ice and rock. These rings make it stand out from other planets.

🎯 Exam Tip: To remember ringed planets, think of "Saturn's rings" as its most famous feature. Jupiter, Uranus, and Neptune also have rings, but Saturn's are the most prominent.

Question 4. The Outer Planets are
(a) Jupiter and Mercury
(b) Venus and Earth
(c) Saturn and Mars
(d) Uranus and Neptune
Answer: (d) Uranus and Neptune
In simple words: The outer planets are far from the Sun and are usually big gas giants. Uranus and Neptune are both large, icy gas giants, located in the outer part of our solar system.

🎯 Exam Tip: Remember that outer planets are also called gas giants, and they are located beyond the asteroid belt, while inner planets are rocky.

Question 5. The Tropic of Cancer faces the Sun directly on
(a) March 21
(b) June 21
(c) September 23
(d) December 22
Answer: (b) June 21
In simple words: On June 21st, the Sun's rays shine straight down on the Tropic of Cancer, marking the start of summer in the northern hemisphere. This day is known as the Summer Solstice.

🎯 Exam Tip: The Tropic of Cancer and Tropic of Capricorn mark the northernmost and southernmost points where the sun can be directly overhead during the solstices.

III. (i) Consider the following statements

Question 1. Consider the following statements:
1. The earth is the third planet in the solar system
2. The Sun is made up of hot gases like Hydrogen and Nitrogen
3. Mercury has no natural satellites
Choose the correct answer using the codes given below.
(a) 1 and 2
(b) 2 and 3
(c) 1 and 3
(d) 2 only
Answer: (c) 1 and 3
In simple words: Statement 1 is true because Earth is indeed the third planet from the Sun. Statement 3 is also true, as Mercury is a small planet very close to the sun with no moons. Statement 2 is incorrect because the Sun is made of Hydrogen and Helium, not Nitrogen.

🎯 Exam Tip: When evaluating multiple statements, break down each statement individually to determine its truthfulness before selecting the combined answer. Factual knowledge about the solar system is key here.

III. (ii) Consider the following statements

Question 1. Consider the following statements:
1. The sun revolves around the earth.
2. Mars is named after the Roman God of war.
3. Uranus appears green
Choose the correct answer using the codes given below.
(a) 1 and 2
(b) 2 and 3
(c) 1 and 3
(d) 3 only
Answer: (b) 2 and 3
In simple words: Statement 1 is false because the Earth orbits the Sun, not the other way around. Statement 2 is true, as Mars gets its name from the Roman god of war. Statement 3 is also true, as Uranus looks green because of methane gas in its atmosphere.

🎯 Exam Tip: Always remember the heliocentric model, where planets orbit the Sun, and review unique characteristics of each planet like color or naming origins to avoid common errors.

III. (iii) Consider the following statements

Question 1. Statement I: Jupiter is the fastest spinning planet in the solar system. Statement II: Neptune is the coldest planet. Which of the statement(s) is/are true?
(a) I is true, II is wrong
(b) I is wrong, II is true
(c) Both the statements are true
(d) Both statements are wrong.
Answer: (c) Both the statements are true
In simple words: Jupiter spins around very quickly, making it the fastest-rotating planet. Neptune is the farthest large planet from the Sun and is known for its extremely low temperatures.

🎯 Exam Tip: Knowing the unique features of each planet, like rotation speed and temperature extremes, is key for these types of questions, as they test specific planetary characteristics.

III. (iv) Consider the following statements

Question 1. Statement I: The earth is inclined at 32 1/2°angle. Statement II: The specific gravity of Saturn is more than that of water. Which of the statement(s) is/are true?
(a) I is true, II is wrong
(b) I is wrong, II is true
(c) Both the statements are true
(d) Both the statement are wrong
Answer: (d) Both the statements are wrong
In simple words: Earth's axis is actually tilted at about 23.5 degrees, not 32.5 degrees. Saturn is known for having a very low density, meaning its specific gravity is less than water, which is why it would float.

🎯 Exam Tip: Double-check specific scientific values like axial tilt and densities, as these are common factual errors in such questions and require precise knowledge.

IV. Answer the following questions

Question 1. What is meant by light year?
Answer: A light-year is the total distance that light travels in one Earth year. Light travels incredibly fast, covering about 300,000 kilometers every second. So, a light-year represents a very large distance in space, used to measure distances to stars and galaxies.
In simple words: A light-year is how far light travels in one year. Light moves extremely fast, so this is a huge distance, not a measure of time.

🎯 Exam Tip: Emphasize that a light-year measures distance, not time, which is a common misconception, and state the definition clearly.

Question 2. Mention the hierarchy of the universe.
Answer: The universe has a specific order of components, from largest to smallest. Starting with the entire Universe, it contains many galaxies, each with numerous solar systems, which in turn have planets orbiting a star, and some planets have natural satellites like moons.
1. Universe
2. Galaxy
3. Solar system
4. Planets
5. Satellites
In simple words: The universe is organized from biggest to smallest: the whole universe, then galaxies, then solar systems, then planets, and finally satellites orbiting planets.

🎯 Exam Tip: When listing a hierarchy, always present the items in a clear order, usually from largest to smallest, to accurately show the structural relationship.

Question 3. How many planets are there in the solar family? Name them.
Answer: There are eight main planets in our solar system. These planets orbit the Sun and each has unique characteristics, forming part of what we call the solar family.
They are:
1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune
In simple words: There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

🎯 Exam Tip: When listing the planets, remember them in order from the Sun to ensure accuracy and completeness in your answer.

V. Mind map