Metals and Non-Metals
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Some other extra questions :
Que1. Name a metal which is non- lustrous and a non – metal which is lustrous.
Ans. Iron (due to corrosion on the surface) is a metal that is non-lustrous and iodine is a non-metal which is lustrous.
Que2. How do metals and non-metals combine ?
Ans. Metals and non metals combine by the transfer of electrons from metals to non-metals to form ionic bonds.
Que3. Why sodium chloride has high melting point ?
Ans. Sodium chloride consists of Na+ and Cl – ions. These are strongly attracted towards each other. To break these strong forces of attraction, a large amount of energy is needed and hence sodium chloride has a high melting point.
Que4. Which metal is more metallic ā sodium or aluminium and why ?
Ans. Sodium is more metallic than aluminium because sodium can lose its electron more easily than aluminium.
Que5. Aluminium is more reactive than iron, yet its corrosion is less than iron. Why ?
Ans. Aluminium is covered with a strong protective layer of oxide which does not peel off easily and thus protects the metal from further corrosion.
Que6. Explain why aluminium reacts with dilute hydrochloric acid slowly in the beginning.
Ans. The surface of aluminium is covered with a strong protective layer of its oxide due to attack of oxygen of the air. Hence, it reacts slowly. When this layer gets dissolved in the acid, fresh surface of aluminium is exposed. The reaction then becomes faster.
Que7. What is galvanization ? How does this process prevent rusting ?
Ans. The process of depositing a thin layer of zinc on the surface of iron is called galvanization. Galvanization prevents iron from rusting since it does not allow air and moisture to come in contact with iron.
Que8. Define the term āalloyā. Write two advantages of making alloys.
Ans. A homogeneous mixture of two or more metals, or a metal and a non-metal, is called an alloy. For example, bronze (Cu = 90%), (Sn = 10%) , steel (Fe = 99.95% and C = 0.05%).
Advantages of making alloys.
(i) The various properties of a metal like malleability, ductility, tensile strength, resistance to corrosion and appearance can be improved by mixing it with other metals or a non-metal.
(ii) The chemical reactivity of a metal can be reduced by making its alloy with merury, i.e., by making amalgam. For example, sodium is a very reactive metal but sodium amalgam is less reactive.
Que9. How is corrosion of iron prevented by coating it with a layer of oil ?
Ans. Corrosion of iron is prevented by coating it with a layer of oil. The reason being that the layer of oil does not allow air and water to reach the surface of iron.
Que10. Why is tungsten metal selected for making filaments of incandescent lamp bulbs ?
Ans. Tungsten metal is used in making filaments of incandescent lamp bulbs because it has high resistance and high melting point.