Extra Questions for Chapter 4 The World of Metals and Non-metals Class 7 Science Curiosity
Class 7 Science The World of Metals and Non-metals Extra Questions
Very Short Answer Questions
Question 1. What happens when magnesium reacts with oxygen?
Answer
Magnesium burns with a dazzling white flame and forms magnesium oxide.
Question 2. What is the nature of magnesium oxide when dissolved in water?
Answer
Magnesium oxide forms a basic solution when dissolved in water.
Question 3. What is the process by which metals like iron develop brown deposits?
Answer
This process is called rusting, and it occurs when iron comes into contact with both air and water.
Question 4. Why are materials like copper and aluminium used in electrical wiring?
Answer
Because they are good conductors of electricity.
Question 5. What is the purpose of applying a protective layer of zinc on iron?
Answer
To prevent rusting.
Question 6. What happens when metals react with oxygen?
Answer
When metals react with oxygen, they form metal oxides, which are usually basic in nature.
Question 7. What is sonority in metals?
Answer
Sonority is the property of metals to produce a ringing sound when struck. Metals like iron and steel are sonorous.
Question 8. What property of metals makes them good for cooking vessels?
Answer
Conduction of heat.
Question 9. What is the property of metals that allows them to be beaten into thin sheets?
Answer
Malleability
Short Answer Questions
Question 1. What is ductility?
Answer
Ductility is the property of materials that allows them to be drawn into wires. Metals such as gold and copper are highly ductile.
Question 2. What is malleability?
Answer
Malleability is the property of materials by which they can be beaten or hammered into thin sheets. Metals like copper, aluminium, and iron possess malleability.
Question 3. How does sonority benefit everyday objects, with an example?
Answer
Sonority allows metals to produce ringing sounds when struck, used in objects like school bells, which ring loudly to signal time.
Question 4. Why is wood considered neither malleable nor brittle?
Answer
Wood is neither malleable because it cannot be flattened like metals, nor brittle because it does not break easily like non-metals, having some flexibility.
Question 5. What is rusting, and name one method to prevent it?
Answer
Rusting is the chemical reaction where iron reacts with oxygen and moisture to form rust. One prevention method is painting the iron surface.
Question 6. Why are gold and silver used in jewellery, and why are only a few metals suitable for this purpose?
Answer
Gold and silver are highly malleable and ductile, allowing them to be shaped into intricate designs and thin sheets. They are also resistant to corrosion, making them ideal for jewellery. However, not all metals possess these qualities, as some are too hard or reactive to be used for jewellery.
Question 7. What happens when metals like copper and aluminium are beaten with a hammer?
Answer
Metals like copper and aluminium become flattened when beaten with a hammer, demonstrating their malleability.
Question 8. Why are metals like iron and copper used in electrical wiring?
Answer
Metals like iron and copper are good conductors of electricity, making them ideal for use in electrical wiring.
Question 9. Why are metals used for cooking utensils?
Answer
Metals are good conductors of heat, which makes them ideal for cooking utensils as they quickly transfer heat to food.
Question 10. What is corrosion?
Answer
Corrosion is the gradual deterioration of metals due to reactions with air, water, or other substances. For example, iron rusts when exposed to moist air.
Question 11. Why is sodium stored in kerosene?
Answer
Sodium reacts vigorously with water and oxygen, generating a lot of heat. Storing sodium in kerosene prevents it from reacting with moisture and air.
Question 12. What is the significance of the Iron Pillar of Delhi, and what does it tell us about ancient Indian metallurgy?
Answer
The Iron Pillar of Delhi is a remarkable example of ancient Indian metallurgy. Despite facing exposure to wind, rain, and intense weather for over 1600 years, it shows very little rust. This indicates advanced techniques in metalworking that allowed for resistance to rusting, demonstrating the high level of skill in metallurgy in ancient India.
Question 13. What is the importance of metals and non-metals in everyday life?
Answer
Metals and non-metals play vital roles in daily life. Metals are used in construction, electrical devices, and tools, while non-metals like oxygen and nitrogen are essential for life and plant growth.
Question 14. Describe the process of rusting and the methods used to prevent it.
Answer
Rusting is the process where iron reacts with oxygen and water, forming brown deposits on its surface. To prevent rusting, methods such as painting, oiling, greasing, or applying a protective layer of zinc (galvanisation) are used. These methods prevent exposure to air and water, which are necessary for rust formation.
Question 15. You are an engineer designing electrical wiring for a new building. Explain why metals are used in wires and non-metals are used to cover them. What might happen if both were made of the same material?
Answer
Metals like copper and aluminium are used in wires because they allow electricity to pass through them easily.
Non-metals like plastic or rubber are used to cover the wires because they do not conduct electricity, and they protect us from getting electric shocks.
If both the wire and the covering were made of metal, the current would leak, and people might get shocked or hurt. That’s why metals and non-metals are both needed in the correct place.
Question 16. Why do you think school bells are made of metal and not plastic or wood? Can you relate this to the property of sonority?
Answer
School bells are made of metal because metals make a clear ringing sound when we hit them. This property is called sonority.
Plastic or wood do not make a loud sound. They produce dull sounds, which cannot be heard from far away.
That’s why metals are used in bells, musical instruments, and dance anklets (ghungroos), as they help produce loud and pleasant sounds.
Long Answer Questions
Question 1. Explain the properties of metals and non-metals and how they differ.
Answer
Metals are generally lustrous, malleable, ductile, and good conductors of heat and electricity. They form basic oxides when they react with oxygen. Non-metals, on the other hand, are usually non-lustrous, brittle, and poor conductors of heat and electricity. They form acidic oxides when they react with oxygen and do not have the properties of malleability and ductility.
Question 2. How do the properties of metals and non-metals influence their uses in everyday life?
Answer
The properties of metals, such as conductivity, malleability, and ductility, make them useful in applications like electrical wiring, construction, and manufacturing tools. Non-metals, though poor conductors, are essential in biological processes, like oxygen for respiration and carbon for life forms, and are also used in the production of fertilizers and water purification.
Question 3. Describe the physical properties of metals and how they differ from non-metals.
Answer
Metals generally exhibit properties like metallic lustre, malleability, ductility, sonority, and high conductivity of heat and electricity. Non-metals, on the other hand, are generally non-lustrous, brittle, and poor conductors of heat and electricity. Metals can be hammered into sheets (malleable) and drawn into wires (ductile), whereas non-metals lack these properties. Non-metals also form acidic oxides when they react with oxygen, while metals typically form basic oxides.
Question 4. How does the reaction of metals and non-metals with oxygen differ?
Answer
Metals generally react with oxygen to form basic metal oxides, such as iron oxide (rust), which is alkaline in nature. Non-metals, on the other hand, form acidic oxides when they react with oxygen, such as sulfur dioxide, which forms sulfurous acid when dissolved in water. This difference in reactions is key to understanding the nature of oxides formed by metals and non-metals.
Question 5. Explain the process of rusting and how it can be prevented.
Answer
Rusting is the process where iron reacts with oxygen and water to form iron oxide (rust), which causes the iron to deteriorate. Rusting can be prevented by methods such as painting, oiling, greasing, or applying a protective layer of zinc (galvanization). These methods protect the iron from direct exposure to air and water, thus preventing corrosion.
Question 6. What are the applications of metals in daily life?
Answer
Metals have numerous applications in daily life due to their distinct properties. For instance, metals like copper and aluminium are used for electrical wiring due to their excellent conductivity. Iron and steel are used in construction and making tools due to their strength and malleability. Precious metals like gold and silver are used in jewellery, while aluminium is used in food packaging materials due to its malleability and low cost. Metals are also used in the manufacturing of machinery, vehicles, and electronics.
Question 7. Discuss the uses of non-metals in everyday life.
Answer
Non-metals like oxygen are essential for respiration, making them crucial for life. Nitrogen is used in fertilizers to enhance plant growth. Carbon is an important element in organic molecules and fuels. Chlorine is used in water purification, while iodine is used as an antiseptic for wounds. Non-metals are also found in medicines, food preservation, and industrial applications like rubber manufacturing and water treatment.
Question 8. Explain the properties of metals and non-metals, with examples for each property.
Answer
Metals and non-metals have distinct properties.
Properties of Metals:
- Malleability: Can be beaten into sheets, e.g., aluminium foil for food wrapping.
- Ductility: Can be drawn into wires, e.g., copper for electrical wiring.
- Sonority: Produce ringing sounds, e.g., iron in school bells.
- Conduction: Good conductors of heat and electricity, e.g., copper in cooking pots.
- Lustre: Shiny appearance, e.g., polished silver.
Properties of Non-Metals:
- Brittleness: Break when struck, e.g., coal shatters.
- Non-lustrous: Dull appearance, e.g., sulfur.
- Poor conduction: Do not conduct heat/electricity, e.g., wood in pot handles.
- Non-sonorous: Produce dull sounds, e.g., wood when dropped.
These properties help classify materials and determine their uses, like metals in tools and non-metals in insulation.
Question 9. Describe the process of rusting and its prevention methods, with examples.
Answer
Rusting is a chemical reaction where iron reacts with oxygen and moisture in the air, forming reddish-brown rust, which weakens iron objects like tools or bridges. It requires both air and water; iron does not rust in dry air or water alone. Prevention methods include:
- Painting: Coating iron with paint, e.g., painting bridges to block air and moisture.
- Oiling/Greasing: Applying oil, e.g., greasing bicycle chains to form a protective layer.
- Galvanisation: Coating with zinc, e.g., galvanised iron buckets to prevent rust.
These methods protect iron structures, saving costs on repairs and ensuring safety, as rust makes objects weak and unsafe.
Question 10. Discuss the importance of non-metals in daily life, with examples from daily life.
Answer:
Non-metals are essential in daily life despite their differences from metals. Examples include:
- Oxygen: Vital for breathing, used in hospitals for patients and in welding processes.
- Carbon: The building block of life, found in proteins and carbohydrates for energy and growth.
- Nitrogen: Used in fertilizers to help plants grow, supporting agriculture.
- Chlorine: Purifies drinking water, ensuring safety.
- Iodine: Used as an antiseptic for wounds, preventing infections.
Unlike metals, which are used in tools and wires, non-metals support life, health, and agriculture. Their poor conductivity, like rubber’s use in electrician gloves, ensures safety. These roles highlight non-metals’ critical contributions to human survival and societal functions.
Question 11. Why do you think the Iron Pillar of Delhi has not rusted even after 1600 years, while modern iron tools rust within a few years if exposed to air and water? What does this tell us about ancient Indian metallurgy?
Answer
The Iron Pillar of Delhi has not rusted because it was made using a special method that protected it from air and water. The iron used in the pillar is very pure, and a special layer formed on it naturally, which stops rusting. This shows that ancient Indian people had great knowledge and skills in making strong and long-lasting metals. They knew how to protect metals from rusting, even without modern machines or chemicals.
Question 12. Imagine a world where all materials were non-metals. How would it affect industries like construction, transportation, or electricity supply? Give at least two examples.
Answer
If everything were made from non-metals, many things around us would not work properly. For example:
- In construction, buildings and bridges would not be strong, because non-metals are weak and break easily.
- In electricity supply, we could not use copper or aluminium wires, as non-metals do not let electricity pass through them.
This would make it hard to live the way we do now, as many tools and machines need metals to work properly.
Question 13. If Anandi wanted to test whether a new shiny material is a metal or non-metal, what simple experiments could she perform at home or school, and why?
Answer
Anandi could try these simple tests:
- She can hit the object gently with a spoon. If it makes a ringing sound, it is probably a metal.
- She can check if the material shines when rubbed. Metals usually have a shiny look called lustre.
- She can see if it can be flattened or bent without breaking (this shows malleability).
- If she has a simple electric circuit, she can connect the material and see if it lets the bulb glow. If it does, it is a good conductor like a metal.
These small tests help her understand the properties of the material.
Question 14. You are designing a kitchen utensil set. Which parts should be made of metal and which of non-metal? Explain your choices based on properties like heat conduction and malleability.
Answer
In the kitchen, cooking pans and pots should be made of metals like aluminium or iron because metals get hot quickly and help in cooking food faster (they are good conductors of heat).
The handles of these utensils should be made of non-metals like plastic or wood, because they do not get hot easily (they are poor conductors). This helps us hold the pan safely without burning our hands.
Also, metals are malleable, so they can be shaped into different cooking tools.
Question 15. In your opinion, which is more crucial to human survival—metals or non-metals? Justify your answer with examples from daily life.
Answer
Non-metals are more important for our survival.
For example:
- Oxygen, a non-metal, is needed for breathing. Without it, we cannot live.
- Carbon is found in our body and in food. It helps us grow and stay healthy.
- Nitrogen is used in fertilizers that help plants grow.
- Chlorine cleans water so we can drink it safely.
These non-metals are a part of our life every day, while metals are useful for making tools and machines. So, for survival, non-metals are more important.
Question 16. Sodium is stored in kerosene, while phosphorus is stored in water. What does this indicate about the reactivity of these non-metals and metals? Can you think of any safety risks if these substances were stored improperly?
Answer
This shows that sodium and phosphorus are very reactive, which means they catch fire or explode easily when they come in contact with air or water.
- Sodium reacts quickly with air and water, so we store it in kerosene to keep it safe.
- Phosphorus catches fire when exposed to air, so it is kept under water to stop it from burning.
If these materials are not stored properly, they can cause fires, burns, or accidents. That’s why it’s important to handle them carefully.
Question 17. Rusting damages iron tools and structures. If you were a scientist, what methods would you explore (besides painting and oiling) to prevent rusting more effectively in humid coastal areas?
Answer
As a scientist, I would try these methods:
- Galvanisation: Coating the iron with zinc, which protects it from rust.
- Using stainless steel: This is a type of iron mixed with other metals that doesn’t rust easily.
- Making a waterproof layer: Using special sprays or materials that stop air and water from touching the iron.
These methods can protect iron tools and save money spent on repairs, especially in areas near the sea where air is moist.
Question 18. Why do you think both malleability and ductility are considered useful properties for metals in industries? Can you think of an example where one is more important than the other?
Answer
Metals are used in factories because they can be:
- Malleable – shaped into thin sheets (like for car bodies or kitchen utensils).
- Ductile – pulled into wires (like for electricity and machines).
In making aluminium foils, malleability is more important because the metal needs to be flattened.
In making electrical wires, ductility is more useful because the metal must be stretched into thin wires. So, both properties are helpful but used in different ways.