๐ Class 7 Science Curiosity – Chapter 4 Solutions
๐ฉ The World of Metals and Non-metals | Amresh Academy
๐ ๐น Let Us Enhance Our Learning
1. Which metal is commonly used to make food packaging materials as it is cheaper, and its thin sheets can be folded easily into any shape?
๐ Answer: (i) Aluminium ๐ฅก
2. Which of the following metal catches fire when it comes in contact with water?
๐ Answer: (iv) Sodium ๐ฅ
3. State with reason(s) whether the following statements are True [T] or False [F].
๐ Answer:
4. Why are only a few metals suitable for making jewellery?
๐ Example: Gold, Silver
5. Match the uses of metals and non-metals given in Column I with the jumbled names of metals and non-metals given in Column II.
๐ Answer:
6. What happens when oxygen reacts with magnesium and sulfur. What are the main differences in the nature of products formed?
๐ Answer:
- Magnesium + Oxygen → Magnesium oxide (basic) ๐งช
- Sulfur + Oxygen → Sulfur dioxide (acidic) ๐ซ️
๐ Difference:
- Metal oxide → Basic
- Non-metal oxide → Acidic
7. Complete the following flow chart: (Flow chart depicts burning magnesium)
๐ Answer:
- Starting material → Magnesium ribbon
- Magnesium + Air + Heat → Magnesium oxide (ash)
- Magnesium oxide + Water → Magnesium hydroxide
- Litmus test:
- Blue → No change
- Red → Turns blue
๐ Conclusion: Solution is basic ๐งช
8. You are provided with the following materials. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why?
Iron, copper, sulfur, coal, plastic, wood, cardboard
๐ Reason:
- Good conductors of heat ๐ฅ
- Others are insulators → not suitable
9. You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?
10. How do the different properties of metals and non-metals determine their uses in everyday life?
๐ Answer:
๐ฉ Metals:
- Conduct electricity → wires ⚡
- Conduct heat → utensils ๐ณ
- Strong → tools ๐ ️
- Lustrous → jewellery ๐
๐ฟ Non-metals:
- Poor conductors → insulation ๐ซ
- Oxygen → breathing ๐ฌ️
- Nitrogen → fertilizers ๐ฑ
- Chlorine → purification ๐ง
11. One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulfur does not react with water, can it be used for this purpose? Justify your answer.
๐ Reason:
- Sulfur is brittle ⚠️
- Does not form protective layer
- Zinc forms strong coating ✔️
12. An ironsmith heats iron before making tools. Why is heating necessary in this process?
✍️ ๐น Very Short Answer Type Questions
What is malleability?
๐ Ability to be beaten into thin sheets ๐จ
Name two metals used to make kitchen utensils.
๐ Aluminium, Copper ๐ณ
What kind of sound do metals make when struck?
๐ Ringing sound ๐ (sonorous)
Which metal remains in liquid form at room temperature?
๐ Mercury ๐ก️
What is rusting?
๐ Formation of brown layer on iron ๐ค
๐ง ๐น Short Answer Type Questions
Why are electrical wires usually made of copper or Aluminium?
๐ Good conductors + ductile ⚡
What happens when magnesium ribbon burns in air?
๐ White flame → magnesium oxide
Why are metals used for making cooking utensils?
๐ Good heat conductors ๐ฅ
What is ductility? Give two examples of ductile metals.
Why do we store sodium metal in kerosene?
๐ Prevents reaction with air/water ⚠️
๐ ๐น Descriptive Questions
Explain the difference between metals and non-metals with examples.
Why does an iron nail rust when exposed to both air and water?
๐ Needs oxygen + moisture ๐ฌ️๐ง
Why are most handles of kitchen tools made from wood or plastic?
๐ Insulators → prevent burns ๐ก️
How does the oxide of sulfur differ from the oxide of magnesium in nature?
What does the Iron Pillar of Delhi teach us about ancient Indian metallurgy?
๐ Advanced rust-resistant technology ๐️
๐ ๐น Exploring Questions
How do metals and non-metals affect our daily lives in different ways?
If sulfur is soft, non-sonorous, and poor conductor, can it be used for making wires? Why or why not?
๐ ❌ No → not ductile, poor conductor
Why is the discovery of iron considered more significant in history than copper, despite copper being discovered earlier?
๐ Iron stronger → better tools ⚔️
Can sulfur be used to prevent rusting of iron like zinc is used in galvanisation? Why or why not?
๐ ❌ No → no protective coating
Which materials would you choose to make a pan for boiling water and why?
๐ Copper/Aluminium → good heat conductors ๐ฅ
