| Class | 10th |
| Subject | Science (NCERT) |
| Category | Important Questions |
Metals and Non-Metals Class 10 Science Chapter 3 Important Question Answer
Q1. Explain reactivity series with examples. Most Important
Ans – The reactivity series is a list of metals arranged in the order of their decreasing reactivity.
Q2. Explain the extraction of metals low in reactivity series.
Ans – Metals low in the activity series are very unreactive. The oxides of these metals can be reduced to metals by heating alone.
For example, cinnabar (HgS) is an ore of mercury. When it is heated in air, it is first converted into mercuric oxide (HgO). Mercuric oxide is then reduced to mercury on further heating.
2HgS(s) + 3O2 (g) 
2HgO(s) + 2SO2 (g)
2HgO(s) 2Hg(l) + O2 (g)
Q3. Write constituents of Bronze and Brass.
Ans – Bronze = Copper (Cu) + Tin (Sn)
Brass = Copper (Cu) + Zinc (Zn)
Q4. What are amphoteric oxides ? Give two examples of amphoteric oxides. Most Important
Ans – Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides.
Example – Aluminium oxide (Al2O3), zinc oxide (ZnO)
Q5. Write brief note on Electrolytic Refining. Most Important
Ans – Many metals, such as copper, zinc, tin, nickel, silver, gold, etc., are refined electrolytically is known as Electrolytic Refining. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas, the insoluble impurities settle down at the bottom of the anode and are known as anode mud.
Q6. In which state ionic compound exists? Why do they have high melting point ? Most Important
Ans – Ionic compounds are solid in physical state. Ionic compounds have high melting point because a large amount of energy is required to break the strong inter-ionic attraction.
Q7. Write electronic configuration of Aluminium (At. No. – 13 ) and Sulphur (At. No. – 16).
Ans – Electronic Configuration of Aluminium = 2, 8, 3
Electronic configuration of Sulphur = 2, 8, 6
Q8. Why is sodium kept in kerosene oil?
Ans – Sodium is highly reactive metal. If it is kept in open it can react with oxygen to catch fire. So, sodium is kept in kerosene to prevent its reaction with oxygen.
Q9. Differentiate between Alloy and Amalgam.
Ans.
| Alloy | Amalgam |
| An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
Example – Bronze, Brass etc. |
An alloy is a homogeneous mixture of a metal in mercury.
Example – zinc-mercury, sodium-mercury etc. |
Q10. What is thermit reaction? Give chemical equation for it. Most Important
Ans – The reaction of iron oxide (Fe2O3) with aluminium is used to join railway tracks or cracked machine parts. This reaction is known as the thermit reaction.
Fe2O3 (s) + 2Al(s) → 2Fe(l) + Al2O3 (s) + Heat
Q11. Identify the metals and metalloids in the following elements:
Sodium ( Na), Silicon ( Si), Germanium (Ge), Lithium (Li).
Ans – Metals : Na, Li,
Metalloids : Si, Ge
Q12. Define the following:
(a) Mineral
(b) Gangue
Ans – (a) The elements or compounds, which occur naturally in the earth’s crust, are known as minerals.
(b) Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.
Q13. Write the chemical equation for the following reactions:
(a) Iron with steam
(b) Calcium with water
Ans – (a) 3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2(g)
(b) Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2 (g)
Q14. Explain the following in context of metals :
(i) Malleability
(ii) Ductility
(iii) Conductor of heat and electricity
(iv) Sonorous
Ans – (i) Malleability : The ability of metals to drawn into thin sheets is called malleability.
(ii) Ductility : The ability of metals to drawn into thin wires is called ductility.
(iii) Conductor of heat and electricity : Metals are good conductor of heat and electricity.
(iv) Sonorous : It is a property of metal in which metals produce a sound on striking a hard surface.
Q15. Differentiate between Calcination and Roasting.
Ans – Calcination : The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.
ZnCO3 (s) ZnO(s) + CO2 (g)
Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting.
2ZnS(s) + 3O2 (g) 2ZnO(s) + 2SO2 (g)
Q16. Name two metals which will displace hydrogen from dilute acids and two metals which will not.
Ans – Metals like Potassium (K), Sodium (Na), Calcium (Ca), Magnesium (Mg) which are more reactive than hydrogen will displace hydrogen from dilute acids and metals like Copper (Cu), Mercury (Hg), Silver (Ag), Gold (Au) will not .
Q17. Name a non-metal that possesses lustuer.
Ans – Iodine
Q18. Name a metal which is liquid at room temperature.
Ans – Mercury
Q19. What happens when metals are burnt in air ? Give one example.
Ans – Metals combine with oxygen to from metal oxides.
Metal + Oxygen → Metal oxide
Example – 2Cu + O2 → 2CuO
In this reaction, copper reacted with oxygen to form copper oxide.
Q20. What happens when metals react with acids ? Give one example.
Ans – Metals react with acids to give a salt and hydrogen gas.
Metal + Dilute acid → Salt + Hydrogen
Example – Mg + 2HCl → MgCl2 + H2
In this reaction, magnesium reacted with hydrochloric acid to give magnesium chloride and hydrogen gas.
Q21. What happens when metals react with water ? Give one example.
Ans – Metals react with water and produce a metal oxide and hydrogen gas.
Metal + Water → Metal oxide + Hydrogen
Example – 2K(s) + 2H2O(l) → 2KOH(aq) + H2 (g) + heat energy
Above example is a reaction of Potassium(metal) with water.
Q22. What happens when water soluble metal oxides are dissolved in water? Give one example.
Ans – Metal oxides that are soluble in water dissolves in it to form metal hydroxide.
Metal oxide + Water → Metal hydroxide
Example – Na2O + H2O → 2NaOH.
Q23. State two ways to prevent the rusting of iron.
Ans – (i) By making alloy
(ii) By applying paint to the surface of iron.
Q24. Differentiate between metal and non-metal on the basis of their chemical properties.
Ans.
| Metals | Non-Metal |
| 1. Metals react with oxygen to form metal oxide. These oxides are basic in nature.
2. Metals are electropositive, lose electrons and become a positive ion. 3. Metals are reducing agents. |
1. Non-metal react with oxygen to form non-metallic oxide. These oxides are acidic in nature.
2. Non-metals are electronegative, gain electrons and become negative ions. 3. Non-metals are oxidising agents. |
Q25. Explain the meanings of malleable and ductility with example.
Ans – Malleable : Those substances which can be beaten into thin sheets are called malleable.
Example – metals like silver, gold, copper etc.
Ductility : Those substances which can be drawn into thin wires are called ductility.
Example – Metals like silver, gold and copper etc.
Q26. Write a short note on electrolytic refining of Copper.
Ans – Electrolytic Refining of Copper : In this process, electrolyte is a solution of acidified copper sulphate. The anode is made up of impure copper , whereas, the cathode is a strip of pure copper. On passing electric current, pure copper from the anode dissolves into electrolyte. An equivalent amount of pure copper from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas, the insoluble impurities settle down at the bottom of the anode. Thus, copper is deposited on the cathode.
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