CBSE Class 10 Science Chapter 3 Metals And Non-Metals Very Short Answer Questions

CBSE Class 10 Science Chapter 3 Metals And Non-Metals Very Short Question And Answer

Question 1. What happens when copper reacts with zinc sulphate?
Answer: No reaction, because copper is less reactive than zinc.

Question 2. Write the composition of aqua-regia.
Answer: A mixture of conc. HCl and conc. HNO₃ is the ratio 3: 1.

Question 3. Give the reason why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer: Because copper is a better conductor of heat than steel.

Question 4. Name and write the symbol of a metal that exists in a liquid state.
Answer:  Mercury (Hg)

Question 5. What is the valency of silicon with atomic number 14?
Answer: 4

Question 6. A green layer is gradually formed on a copper plate left exposed to air for a week in a bathroom. What could this green substance be?
Answer: Due to the formation of basic copper carbonate.

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Question 7. Name the metal which has a very low melting point and can melt with the heat of your palm.
Answer: Gallium

Question 8. Arrange the following metals in the decreasing order of reactivity. Na, K, Cu, Ag
Answer: Na, K, Cu, Ag.

Question 9. Give the composition of the alloys-brass’ and ‘bronze’.
Answer:

Brass-Cu and Zn

Bronze-Cu and Tin

Question 10. An alloy has a low melting point and is, therefore, used for electrical fuse. Name the alloy and write its constituents.
Answer: Solder, Pb and Sn.

Question 11. What is the formula of rust?
Answer: Fe₂O₃.xH₂O

Question 12. Name one metal and a non-metal found in a liquid state at room temperature.
Answer: Metal-mercury and Non-metal-bromine

Question 13. Name two metals which react with dil. HNO₃ to evolve H₂ gas.
Answer: Magnesium (Mg) and manganese (Mn).

Question 14. Why oxides of highly reactive metals cannot be reduced by carbon?
Answer: This is because these metals have more affinity for oxygen than carbon.

Question 15. Name any one metal which reacts neither with cold water nor with hot water but reacts with heated steam to produce hydrogen gas.
Answer: Iron (Fe), aluminium (Al) and zinc (Zn) do not react either with cold or hot water. They react with steam to form metal oxide and hydrogen,

Example:

3Fe(s) + 4H₂O(g)→ Fe₃O₄(s) + 4H₂(g)

Question 16. Among the metals-sodium, calcium, aluminium, copper and magnesium, name the metal which reacts with water only on boiling.
Answer: Magnesium

Question 17. What is formed when sodium absorbs moisture from air? Give equation also.
Answer: It forms sodium hydroxide.

⇒ \(2 \mathrm{Na}+2 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{NaOH}+\mathrm{H}_2\)

Question 18. Why the sulphide and carbonate ores are converted into oxides?
Answer: It is because it is easier to obtain a metal from its oxide, as compared to its sulphide and carbonates.

Question 19. Why do we use copper and aluminium wire for the transmission of electric current?
Answer: Because they are a good conductor of heat and electricity.

Question 20. Name two metals which have very low melting points.
Answer:

1. Caesium
2. Gallium

Question 21. Name a non-metal which is lustrous and a metal which a non-lustrous.
Answer: Iodine is a non-metal which is lustrous. Iron is a metal which is non-lustrous.

Question 22. Write the balanced chemical equation for the reaction: Aluminium when heated in air. Write the name of the product.
Answer:

⇒ \(4 \mathrm{Al}+3 \mathrm{O}_2 \longrightarrow \underset{\text { (Aluminium oxide) }}{2 \mathrm{Al}_2 \mathrm{O}_3}\)

Question 23. Why do ionic compounds not conduct electricity in the solid state?
Answer: The movement of ions in the solid state is not possible due to their rigid structure.

Question 24. A non-metal X exists in two different forms, Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y, and Z.
Answer:

X Carbon Y = Diamond Z = Graphite.

Question 25. Name a non-metal which is lustrous and a metal which is non-lustrous.
Answer: Iodine and Iron

Question 26. The way, metals like sodium, magnesium and iron react with air and water is an indication of their relative positions in the ‘reactivity series’. Is this statement true? Justify your answer with examples.
Answer: Yes. It is the most reactive. Sodium reacts with cold water, while magnesium reacts with hot water. Iron reacts only with steam.

Question 27.

1. X+YSO₄ → XSO₄+ Y
2. Y + XSO₄ → No reaction

Out of the two elements ‘X’ and ‘Y, which is more reactive and why?
Answer:

‘X’ is more reactive than ‘Y’ because it displaces ‘Y’ from its salt solution.

Question 28. When a metal X is treated with cold water, it gives a base Y with the molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y, and Z.
Answer: X’ is Sodium, Y is Sodium hydroxide, and ‘Z’ is H₂(g).

Question 29. What is an alloy? State the constituents of solder.
Answer:  An alloy is a homogeneous mixture of two or more two metals, which have nearly the same atomic size. Solder consists of lead and tin.

Question 30. What are amphoteric oxides? Choose the amphoteric oxides from among the following oxides:
Answer: Na₂O, ZnO, Al₂O₃, CO₂, H₂O

Question 31. What is 24-carat gold? How will you convert it into 18-carat gold?
Answer: 24-carat gold is pure gold. It is converted into 18-carat gold by adding 6 parts of Copper to 18 parts of gold, i.e., 75% Au and 25% Cu.

Question 32. Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?
Answer: It is easier to obtain metal from its oxide, as compared to its sulphides and carbonates.

Question 33. Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), are treated with HNO₃, hydrogen is not liberated, why?
Answer:  HNO₃ is not only an acid, but it is also a strong oxidizing agent. It oxidizes the hydrogen formed into water, itself HNO₃ is reduced to NO₂ or N₂O.

Question 34. An element forms an oxide, Al₂O, which is acidic. Identify A as metal or non-metal.
Answer: Since an oxide of the element is acidic, therefore, I will be a non-metal.

Question 35. Give two examples of each of the metals that are good conductors and poor conductors of heat respectively.
Answer: Good conductors of heat-Silver, copper and aluminium Poor conductors of heat-Lead and mercury

Question 37. Name two metals which are found in nature in the free state.
Answer: Gold and Platinum

Question 36. Write two examples of each of the metals that are good conductors and poor conductors of heat respectively.
Answer: Good conductors of heat are copper and silver. Poor conductors of heat are lead and mercury.

Question 37. Name one metal and one non-metal that exist in a liquid state at room temperature. Also, name two metals having melting points less than 310 K (37°C).
Answer: Metal in the liquid state is mercury, and non-metal in the liquid state is bromine. Gallium (Ga) and Caesium (Cs) have melting points below 310 K.

Question 38. Name two metals which will displace hydrogen from dilute acids and two metals which will not.
Answer: Magnesium and zinc would displace hydrogen from dilute acids, whereas metals low in reactivity series like copper and silver will not displace hydrogen from dilute acids.

Question 39. State two ways to prevent the rusting of iron.
Answer: Rusting of iron can be prevented by painting, oiling, greasing, galvanising, chrome painting, anodising or making alloys.

Question 40. What type of oxides are formed when non-metals combine with oxygen?
Answer: Acidic oxides are formed when non-metals combine with oxygen.

Question 41. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is kept immersed in kerosene oil as it reacts vigorously with air to catch fire.

Question 42. Which metals do not corrode easily?
Answer: Metals which are below in the activity series like gold, silver, and platinum do not corrode easily.

Question 43. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution.  The bangles sparkled like new but their weight was reduced drastically. The lady was upset, but after a futile argument, the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer: Aqua Regina mixture of concentrated hydrochloric acid and concentrated nitric acid. in the ratio of 3: 1, since it dissolves gold.

Question 44. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer: Iron (steel) reacts with hot water, but copper does not.

Question 45. What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?
Answer: Solder is an alloy of lead (50%) and tin (50%). It has a lower melting point than lead, as well as tin. So it is suitable for welding electric wires.