Imp Questions For All Chapters – General Science Class 8
Short Questions
1. What is a star?
- A star is a huge, glowing ball of hot gases that produces light and heat.
2. Which is the nearest star to Earth?
- The Sun is the nearest star to Earth.
3. What is the name of our galaxy?
- Our galaxy is called the Milky Way.
4. What is a light year?
- A light year is the distance that light travels in one year (about 9.46 trillion km).
5. How fast does light travel?
- Light travels at 300,000 km per second.
6. How much time does light take to reach Earth from the Sun?
- Light takes 8 minutes to reach Earth from the Sun.
7. How are stars formed?
- Stars are formed from interstellar clouds of gas and dust due to gravitational contraction.
8. What is nuclear fusion in stars?
- Nuclear fusion is the process where hydrogen atoms combine to form helium, releasing energy.
9. What determines the life cycle of a star?
- The mass of the star determines how it evolves and how it ends.
10. What are the three possible end stages of a star?
- A star can end as a white dwarf, neutron star, or black hole.
11. What is a white dwarf?
- A white dwarf is the small, dense, and hot remaining core of a low-mass star.
12. Which stars end their life as neutron stars?
- Large stars (8 to 25 times the Sun’s mass) end as neutron stars after a supernova.
13. What is a black hole?
- A black hole is a region in space where gravity is so strong that nothing, not even light, can escape.
14. Why is a black hole called “black”?
- A black hole does not emit light, so it appears completely black.
15. What happens when a massive star dies?
- It undergoes a supernova explosion and becomes a neutron star or black hole.
16. What is a supernova?
- A supernova is a powerful explosion that occurs when a massive star runs out of fuel.
17. What will happen to the Sun at the end of its life?
- The Sun will become a red giant, then shrink into a white dwarf.
18. What is the relationship between a star’s mass and its life span?
- Smaller stars live longer, while larger stars burn fuel faster and die sooner.
19. How many stars are in the Milky Way galaxy?
- There are about 100 billion (10¹¹) stars in the Milky Way.
20. Why do stars twinkle?
- Stars twinkle due to the movement of air in Earth’s atmosphere, which bends their light.
Long Questions
1. How are stars formed?
- Stars are formed from huge interstellar clouds of gas and dust in space. Due to gravity, these clouds contract, increasing temperature and pressure. When the core becomes hot enough, nuclear fusion starts, and a star is born.
2. What happens when a star runs out of fuel?
- When a star uses up its hydrogen fuel, its core contracts, and it expands into a red giant or supergiant. The outer layers are shed, and the remaining core collapses into a white dwarf, neutron star, or black hole. The end stage depends on the star’s mass.
3. What is the life cycle of the Sun?
- The Sun will first expand into a red giant as its hydrogen fuel runs out. Then, it will shed its outer layers, forming a planetary nebula, and shrink into a white dwarf. Over billions of years, the white dwarf will cool and fade away.
4. What is the difference between a neutron star and a black hole?
- A neutron star is a dense collapsed core left after a supernova explosion of a medium-sized star. A black hole forms when a massive star collapses completely, creating a region where gravity is so strong that nothing can escape. Both are extremely dense objects.
5. What is a supernova, and why does it happen?
- A supernova is a powerful explosion that occurs when a large star runs out of nuclear fuel. The star’s core collapses, and the outer layers are blasted into space, releasing huge amounts of energy. After a supernova, the remaining core becomes a neutron star or black hole.
6. Why do stars evolve over time?
- Stars evolve because they burn hydrogen into helium, producing energy and heat. Over time, the fuel decreases, causing changes in temperature, size, and brightness. Eventually, stars become white dwarfs, neutron stars, or black holes, depending on their mass.
7. Why does the Sun not become a black hole?
- The Sun is not massive enough to become a black hole after it dies. Instead, it will expand into a red giant, then shed its outer layers, and finally shrink into a white dwarf. Only stars more than 25 times the Sun’s mass become black holes.
8. How do scientists measure the distance between stars?
- Scientists measure distances using a unit called the light year, which is the distance light travels in one year (about 9.46 trillion km). They also use parallax method and brightness comparisons. These methods help in studying faraway stars and galaxies.
9. What are the three end stages of stars?
- A white dwarf is the small, hot core left after a low-mass star dies. A neutron star forms when a medium-sized star collapses after a supernova. A black hole is created when a very massive star collapses completely, forming an object with extreme gravity.
10. Why do black holes appear black?
- Black holes appear black because their gravity is so strong that not even light can escape. Since we cannot see them directly, scientists detect them by observing their effect on nearby stars and gas clouds. They are one of the most mysterious objects in space.
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