General Science Important Questions Chapter 7 Metals and Nonmetals Class 8 Maharashtra Board

Imp Questions For All Chapters – General Science Class 8

Short Questions

1. What are metals?

• Metals are elements that are shiny, strong, and good conductors of heat and electricity, like iron and copper.

2. What are nonmetals?

• Nonmetals are elements that are brittle, poor conductors of heat and electricity, and dull in appearance, like oxygen and sulfur.

3. Give two examples of metals.

• Gold (Au) and Aluminum (Al).

4. Give two examples of nonmetals.

• Oxygen (O₂) and Nitrogen (N₂).

5. What are metalloids?

• Metalloids are elements that have properties of both metals and nonmetals, like silicon (Si) and boron (B).

6. Which metal is liquid at room temperature?

• Mercury (Hg) is a liquid metal at room temperature.

7. Which nonmetal is liquid at room temperature?

• Bromine (Br) is a liquid nonmetal at room temperature.

8. What is ductility?

• Ductility is the property of metals to be drawn into thin wires (e.g., copper wires).

9. What is malleability?

• Malleability is the ability of metals to be hammered into thin sheets (e.g., aluminum foil).

10. Why is gold used to make jewelry?

• Gold is shiny, does not rust, and is easy to shape, making it perfect for jewelry.

11. Which metals are good conductors of heat?

• Silver and copper are the best conductors of heat.

12. Which nonmetal is a good conductor of electricity?

• Graphite (a form of carbon) is a good conductor of electricity.

13. What happens when metals react with oxygen?

• Metals form metal oxides, which are basic in nature (e.g., magnesium oxide).

14. What happens when nonmetals react with oxygen?

• Nonmetals form nonmetal oxides, which are acidic in nature (e.g., carbon dioxide).

15. What is corrosion?

• Corrosion is the slow destruction of metals due to reaction with air and water (e.g., rusting of iron).

16. What is an alloy?

• An alloy is a mixture of two or more metals, or a metal with a nonmetal (e.g., brass, steel).

17. Why is iron coated with zinc in galvanization?

• Zinc protects iron from rusting by forming a protective layer.

18. Why is sodium stored in kerosene?

• Sodium is highly reactive with air and water, so it is stored in kerosene to prevent accidents.

19. What is the composition of 22-carat gold?

• 22-carat gold contains 91.66% gold and 8.34% copper or silver for strength.

20. Name two noble metals.

• Gold (Au) and Silver (Ag).

Long Questions

1. What is the difference between metals and nonmetals?

• Metals are shiny, strong, and good conductors of heat and electricity, while nonmetals are brittle, dull, and poor conductors. Metals can be shaped into sheets and wires, but nonmetals break easily when hit.

2. Why is sodium stored in kerosene?

• Sodium is a very reactive metal that catches fire when it comes in contact with air or water. Storing it in kerosene prevents it from reacting with air or moisture, making it safe to handle.

3. Why is iron coated with zinc in galvanization?

• When iron is exposed to air and water, it rusts and weakens over time. By coating it with zinc, a protective layer is formed, which prevents rusting and increases durability.

4. What are the uses of noble metals?

• Noble metals like gold, silver, and platinum are used in jewelry, medals, and electronic devices because they do not rust. They are also used in medical instruments and as catalysts in industries.

5. What are the disadvantages of corrosion?

• Corrosion damages metal objects, making them weak and brittle. It causes huge losses in industries, as bridges, buildings, and vehicles require constant maintenance and repair due to rusting.

6. What is the difference between rusting of iron and green coating on copper?

• Iron rusts to form reddish-brown iron oxide when it reacts with air and water. Copper forms a green layer of copper carbonate when it reacts with carbon dioxide and moisture in the air.

7. What are the metals used in making brass and bronze?

• Brass is made of copper and zinc, while bronze is made of copper and tin. Both alloys are stronger, more durable, and do not rust easily, making them useful for making utensils, statues, and musical instruments.

8. What is the composition of 22-carat gold?

• Pure gold is too soft for making jewelry, so 22-carat gold contains 91.66% gold and 8.34% copper or silver. This mixture makes gold stronger and more durable, preventing bending or breaking.