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Chapter 4 - Materials : Metals and Non-Metals Class 8 questions





Fill in the blanks:

1. Metal react with oxygen to produce ................oxides and non-metal react with oxygen to produce................oxides.
2. The presence of .............. and ..................are necessary for iron to rust.
3. ...................is used for making X-ray shields.
4. .....................non-metals is used in fluorescent bulbs to display advertisements.
5. ....................element is used for making pencil lead.
6. .....................and .....................are lustrous non-metals.
7. .....................is the only non-metals that exist as liquid at room temperature.
8. The property of metals by which it can be beaten into sheets is called.................
9. .....................metal can be cut with knife.
10. ......................non-metal is used for vulcanisation of rubber.
11. .......................metal is used in processed food packaging.
12. Process of coating metals with zinc is called.......................
13. Elements that possess properties of both metals and non-metals are called.............
14. ....................is a pure chemical substance consisting of only one type of atoms.
15. Metal react with dilute acids to form...................... and.......................
Answer: 1. Basic, acidic
2. Air, water
3. Lead
4. Neon
5. Graphite
6. Graphite, iodine
7. Bromine
8. Malleability
9. Sodium
10. Sulphur
11. Nitrogen
12. Galvanization
13. Metalloid
14. Element
15. Salt, hydrogen gas


Short answers:

1. Why is gold used for making jewellery?
Answer. Gold does not easily react with other substances. It is an unreactive metal and once polishes, it retains their shine for a long time, therefore, it is used for making jewellery.
2. What do you mean by corrosion?
Answer. Corrosion is used to describe the process by which minerals such as metals are slowly eaten away when exposed to air and moisture.
3. No gas is released when sulphur is added to dilute HCl?
Answer. No gas is releases when sulphur is added to dilute HCl because non-metals do not react with dilute HCl and sulphur is a non-metal.
4. Why are electrical cables made from copper?
Answer. Since copper is a good conductor of electricity, it is used in electrical cables.
5. Why do copper vessels develop a greenish layer when exposed to moist air?
Answer. Copper vessel gets corroded in the presence of moist air that is carbon dioxide and water to form green coating of a substance called basic copper carbonate.
6. Which non-metal is considered to be backbone of the electronics industry?
Answer. Silicon is considered to be the backbone of electronics industry.
7. Why is sodium metal stored under kerosene?
Answer. Sodium metal which react vigorously with the oxygen present in air at room temperature to form sodium oxide. Hence, sodium is stored under kerosene to prevent its reaction with oxygen and moisture present in air.
8. Write the difference between metal oxides and non-metal oxides?
Answer. Metal oxides formed are basic in nature, when dissolved in water they form bases which turn red litmus into blue whereas non-metal oxides are acidic in nature, when dissolve in water they form acids which turn blue litmus into red.
9. Silver is more likely to tarnish near a petroleum refinery than in a place far away? Explain why?
Answer. Silver does not get easily corroded in unpolluted air, however, if the air is polluted with sulphur compounds such as hydrogen sulphide then silver reacts with it to form a black coating of silver sulphide.
10. What are noble metals?
Answer. Silver and gold are present at the bottom of the reactivity series of metals. They are unreactive metals and do not react with water, acids and alkalis. They therefore, occur n free state in nature. So they are noble metals.


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