NCERT Solutions for Class 7 science Chapter 4: The World of Metals and Non metals Class 7

Can you give some examples of metal sheets? (Page 43)
Answer:
Some examples of metal sheets are silver foil and aluminium foil.

Can you name some metals that are used for making cooking vessels? (Page 46)
Answer:
Metals like aluminium, copper, and stainless steel are commonly used for making cooking vessels.

Have you ever seen an electrician using a screwdriver? What type of material is used for making its handle? (Page 47)
Answer:
Yes. The handle of a screwdriver is usually made of plastic or rubber.

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?
(i) Aluminium
(ii) Copper
(iii) Iron
(iv) Gold
(i) Aluminium

Which of the following metal catches fire when it comes in contact with water?
(i) Copper
(ii) Aluminium
(iii) Zinc
(iv) Sodium
(v) Sodium

State with reason(s) whether the following statements are True [T] or False [F].
(i) Aluminium and copper are examples of non-metals used for making utensils and statues.
(ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red.
(iii) Oxygen is a non-metal essential for respiration.
(iv) Copper vessels are used for boiling water because they are good conductors of electricity.
Answer:

Why are only a few metals suitable for making jewellery?
Answer:
Only a few metals are suitable for making jewellery because they are lustrous. These metals are also soft, which allows them to be easily shaped into various designs. Also, they do not react easily with air or water, so they do not rust or lose their shine over time.

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.

What happens when oxygen reacts with magnesium and sulphur. What are the main differences in the nature of products formed?
Answer:
When oxygen reacts with magnesium, it forms magnesium oxide, which is a basic oxide and turns red litmus paper to blue. However, when oxygen reacts with sulphur, it forms sulphur dioxide, which is an acidic oxide and turns blue litmus paper to red.

Complete the following flowchart:

Answer:

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?
Answer:
For boiling water, the pan must be made of a material that is a good conductor of heat. Among the given materials, only iron and copper are metals and both are good conductors of heat. However, copper is the best choice because it is highly resistant to rust compared to iron. Therefore, a pan made of copper is the most suitable choice for boiling water.

You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?
Answer:
The iron nail dipped in oil will not rust because the oil prevents the iron nail from coming into contact with air or moisture. It forms a protective layer on the metal, which prevents rusting.

How do the different properties of metals and non-metals determine their uses in everyday life?
Answer:
Metals and non-metals have various properties that make them useful in our everyday life.

One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulphur does not react with water, can it be used for this purpose? Justify your answer.
Answer:
No, sulphur cannot be used to protect iron from rusting. While sulphur does not react with water, it does not have the property of forming a protective layer over iron like zinc. It cannot prevent air and moisture from coming into contact with the iron.

An ironsmith heats iron before making tools Why is heating necessary in this process?
Answer:
For making tools, a ironsmith first heats a piece of iron until it becomes red-hot. This is because heating makes the iron soft, more malleable and easier to bend, hammer and mould into the desired shape for tools.