Class 10 Science · Chapter 3

Metals and Non-metals

344 Class 10 Science questions on Metals and Non-metals from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 14 of 18

1. Q261 CBSE 2023
   Almost all metals combine with oxygen to form metal oxides. Metal oxides are generally basic in ​nature. But ​some metal oxides ​show both ​basic as ​well as acidic behaviour. Different metals show different reactivities ​towards oxygen. Some ​react vigorously while some ​do not react at all.

   1. (a)What happens when copper is heated in air ? (Give the equation of the reaction involved).[1]
   2. (b)Why are some metal oxides categorized as amphoteric ? Give one example.[1]
   3. (c)(i)Complete the following equations : (i) ${\text{Na}}_2{\text{O}}_{(s)}+{\text{H}}_2{\text{O}}_{(l)}⟶$ (ii) ${\text{Al}}_2{\text{O}}_3+2\text{NaOH}⟶$[2]
   4. (c)(ii)OR : On burning Sulphur in oxygen a colourless gas is produced. (i) Write chemical equation for the reaction. (ii) Name the gas formed. (iii) State the nature of the gas. (iv) What will be the action of this on a dry litmus paper ?[2]
   Show answer

   Copper forms black copper oxide; amphoteric oxides react with acids and bases; sodium oxide gives sodium hydroxide; sulphur burns to acidic sulphur dioxide.

   (a) The shiny reddish brown surface of copper becomes coated with a black layer of copper(II) oxide: $2\text{Cu}+{\text{O}}_2\stackrel{\Delta }{\to }2\text{CuO}$. (b) Because they react with acids **and** with bases, giving a salt and water in both cases: towards an acid they behave as a base and towards a base they behave as an acid. Example: aluminium oxide, ${\text{Al}}_2{\text{O}}_3$ (zinc oxide, $\text{ZnO}$, is another). (c)(i) (i) ${\text{Na}}_2{\text{O}}_{(s)}+{\text{H}}_2{\text{O}}_{(l)}⟶2{\text{NaOH}}_{(aq)}$; (ii) ${\text{Al}}_2{\text{O}}_3+2\text{NaOH}⟶2{\text{NaAlO}}_2+{\text{H}}_2\text{O}$, giving sodium aluminate and water. OR (c)(ii) (i) ${\text{S}}_{(s)}+{\text{O}}_{2(g)}\stackrel{\Delta }{\to }{\text{SO}}_{2(g)}$; (ii) the gas is sulphur dioxide; (iii) it is acidic in nature, being the oxide of a non-metal, and it dissolves in water to give sulphurous acid; (iv) it has **no** action on dry litmus paper, because an acid shows its acidic character only in the presence of water. On **moist** blue litmus paper the same gas turns the paper red.

   Step-by-step solution →
2. Q262 CBSE 2023
   The melting points and boiling points of some ionic compounds are given below : These compounds are termed ​ionic because they are formed by the transfer of electrons ​from a metal to a non-metal. The electron ​transfer in such compounds is controlled by the ​electronic ​configuration of the ​elements involved. Every element tends ​to attain a completely filled valence shell of its nearest noble gas or a stable octet.

   Melting points and boiling points of some ionic compounds

   Compound	Melting Point (K)	Boiling Point (K)
   NaCl	1074	1686
   LiCl	887	1600
   CaCl₂	1045	1900
   CaO	2850	3120
   MgCl₂	981	1685

   1. (a)Show the electron transfer in the formation of magnesium chloride.[1]
   2. (b)List two properties of ionic compounds other than their high melting and boiling points.[1]
   3. (c)(i)While forming an ionic compound say sodium chloride how does sodium atom attain its stable configuration ?[2]
   4. (c)(ii)OR : Give reasons : (i) Why do ionic compounds in the solid state not conduct electricity ? (ii) What happens at the cathode when electricity is passed through an aqueous solution of sodium chloride ?[2]
   Show answer

   Magnesium loses two electrons to two chlorine atoms; ionic solids are hard and brittle; sodium loses one electron to reach neon's stable configuration.

   (a) $\text{Mg}(2,8,2)$ loses its two valence electrons, one to each of two chlorine atoms, becoming ${\text{Mg}}^{2+}(2,8)$, the configuration of neon; each $\text{Cl}(2,8,7)$ gains one electron to become ${\text{Cl}}^{-}(2,8,8)$, the configuration of argon, and the ions combine as ${\text{Mg}}^{2+}+2{\text{Cl}}^{-}⟶{\text{MgCl}}_2$. (b) They are hard, brittle crystalline solids because of the strong electrostatic attraction between the ions; and they are generally soluble in water but insoluble in organic solvents such as kerosene and petrol. (They also conduct electricity when molten or in solution but not when solid.) (c)(i) Sodium, $2,8,1$, has one electron in its outermost shell. It gives that electron to chlorine and becomes ${\text{Na}}^{+}$ with the configuration $2,8$ -- a completely filled outer shell, the same as neon -- and the ${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ ions are then held together by strong electrostatic attraction. OR (c)(ii)(i) In the solid state the ions are held at fixed positions in the crystal lattice by strong electrostatic forces and there are no free electrons, so there are no mobile charge carriers and no current can flow. (ii) Hydrogen gas is liberated at the cathode: $2{\text{H}}^{+}+2e^{-}⟶{\text{H}}_2$, and sodium hydroxide is formed in the solution near the cathode (chlorine is given off at the anode).

   Step-by-step solution →
3. Q263 CBSE 2023
   Metals are required for ​a variety of purposes. For this ​we need their extraction from their ores. Ores mined from the earth are ​usually contaminated with ​many impurities which must be removed prior to the extraction ​of metals. The extraction of ​pure metal involves the following steps :

   1. (1)Concentration of ore
   2. (2)Extraction of the metal from the concentrated ​ore
   3. (3)Refining of the metal

   1. (a)Name an ore of Mercury and state the form in which Mercury is present in it.[1]
   2. (b)What happens to zinc carbonate when it is heated strongly in a limited supply of air ?[1]
   3. (c)(i)The reaction of a metal A with ${\text{Fe}}_2{\text{O}}_3$ is highly exothermic and is used to join railway tracks. (I) Identify the metal A and name the reaction taking place. (II) Write the chemical equation for the reaction of metal A with ${\text{Fe}}_2{\text{O}}_3$.[2]
   4. (c)(ii)OR : We cannot use carbon to obtain sodium from sodium oxide. Why ? State the reactions taking place at cathode and anode during electrolytic reduction of sodium chloride.[2]
   Show answer

   Cinnabar is an ore of mercury; zinc carbonate gives zinc oxide and carbon dioxide; A is aluminium (thermite reaction); sodium needs electrolysis, not carbon.

   (a) Cinnabar, $\text{HgS}$. Mercury is present in it in the combined state as its sulphide, mercury(II) sulphide. (b) It is calcined: zinc carbonate decomposes to zinc oxide and carbon dioxide, ${\text{ZnCO}}_3\stackrel{\Delta }{\to }\text{ZnO}+{\text{CO}}_2$. (c)(i)(I) Metal A is aluminium (Al). The reaction is the thermite reaction, a highly exothermic displacement (redox) reaction in which aluminium reduces iron(III) oxide; the molten iron produced is used to weld broken railway tracks. (II) $2\text{Al}+{\text{Fe}}_2{\text{O}}_3⟶{\text{Al}}_2{\text{O}}_3+2\text{Fe}+\text{heat}$. OR (c)(ii) Sodium is a highly reactive metal standing far above carbon in the reactivity series, so it has a greater affinity for oxygen than carbon has; carbon therefore cannot reduce ${\text{Na}}_2\text{O}$. Sodium is obtained by electrolytic reduction of molten sodium chloride: at the cathode ${\text{Na}}^{+}+e^{-}⟶\text{Na}$, and at the anode $2{\text{Cl}}^{-}⟶{\text{Cl}}_2+2e^{-}$.

   Step-by-step solution →
4. Q264 CBSE 2023
   On the basis of reactivity metals are grouped into three ​categories —

   1. (i)Metals of ​low reactivity
   2. (ii)Metals of medium reactivity
   3. (iii)Metals of high reactivity Therefore metals are extracted in pure form ​from their ores on ​the basis of their chemical properties. Metals of high reactivity are extracted from their ores by electrolysis of the ​molten ore. Metals of low reactivity are extracted from ​their sulphide ores, which are converted into their oxides. ​The ​oxides of these metals are reduced to metals by simple heating.

   1. (a)Name the process of reduction used for a metal that gives vigorous reaction with air and water both.
   2. (b)Carbon cannot be used as a reducing agent to obtain aluminium from its oxide ? Why ?
   3. (c)(i)Describe briefly the method to obtain mercury from cinnabar. Write the chemical equation for the reactions involved in the process.
   4. (c)(ii)OR : Differentiate between roasting and calcination giving chemical equation for each.
   Show answer

   Highly reactive metals need electrolytic reduction, and carbon cannot reduce alumina; mercury comes from cinnabar by roasting, then heating the oxide.

   (a) Electrolytic reduction — the molten ore (or molten chloride) is electrolysed and the metal is deposited at the cathode. Metals that react vigorously with both air and water, such as sodium and potassium, are at the top of the reactivity series and can be obtained only this way (calcium, magnesium and aluminium are also obtained by electrolysis, although magnesium does not react with cold water and aluminium reacts only with steam). (b) Because aluminium is **more** reactive than carbon: it stands above carbon in the reactivity series and has a greater affinity for oxygen, so carbon cannot take the oxygen away from ${\text{Al}}_2{\text{O}}_3$. Aluminium is therefore obtained by electrolytic reduction of molten alumina. (c)(i) Cinnabar is $\text{HgS}$. It is first **roasted** — heated strongly in air — to give mercury(II) oxide, and that oxide is then heated further, when it decomposes to the metal; the mercury vapour is condensed and collected: $2\text{HgS}+3{\text{O}}_2\stackrel{\Delta }{\to }2\text{HgO}+2{\text{SO}}_2$ and $2\text{HgO}\stackrel{\Delta }{\to }2\text{Hg}+{\text{O}}_2$. (c)(ii) OR : Roasting is the strong heating of a **sulphide** ore in **excess air** to convert it into the oxide — $2\text{ZnS}+3{\text{O}}_2\stackrel{\Delta }{\to }2\text{ZnO}+2{\text{SO}}_2$; calcination is the strong heating of a **carbonate** ore in a **limited supply of air** or in its absence to convert it into the oxide — ${\text{ZnCO}}_3\stackrel{\Delta }{\to }\text{ZnO}+{\text{CO}}_2$.

   Step-by-step solution →
5. Q265 CBSE 2023
   The iron pillar in ​Qutab ​Minar complex in ​Delhi was ​built 1600 years ago. It is still standing intact and shows no signs of rusting even today. This shows that the ​ancient metallurgists of India in those times had ​fully developed metallurgical processes as well as the techniques of protection of different metals. The protection of metals, ​was done by several processes ​like coating of a thin film of another metal, alloying etc.

   1. (a)Where is iron placed in the reactivity series of metals ? Write the form/forms in which its ores are found in nature.[1]
   2. (b)Differentiate between roasting and calcination.[1]
   3. (c)(i)Explain any two methods that are employed to prevent rusting/corrosion of metals.[2]
   4. (c)(ii)OR : Why is aluminium used to join railway tracks or the cracked machine parts of ‘iron’ ? Write a balanced chemical equation for the reaction which occurs.[2]
   Show answer

   Iron is in the middle of the reactivity series; roasting suits sulphide ores and calcination carbonate ores; zinc coating prevents rusting.

   (a) Iron is placed in the **middle** of the reactivity series - below K, Na, Ca, Mg and Al, and above Cu, Hg, Ag and Au. Being moderately reactive it is never found free; its ores occur chiefly as **oxides** - haematite ${\text{Fe}}_2{\text{O}}_3$ and magnetite ${\text{Fe}}_3{\text{O}}_4$ - and also as the sulphide iron pyrites ${\text{FeS}}_2$ and the carbonate siderite ${\text{FeCO}}_3$. (b) Roasting: the ore is heated strongly in the **presence** of excess air; it is used for **sulphide** ores, e.g. $2\text{ZnS}+3{\text{O}}_2\stackrel{\Delta }{\to }2\text{ZnO}+2{\text{SO}}_2$. Calcination: the ore is heated strongly in the **absence** or limited supply of air; it is used for **carbonate** ores, e.g. ${\text{ZnCO}}_3\stackrel{\Delta }{\to }\text{ZnO}+{\text{CO}}_2$. Both give the metal oxide. (c)(i) Any two of: (1) Painting, oiling or greasing - a barrier film that keeps air and moisture off the iron surface, so rusting cannot begin. (2) Galvanisation - coating the iron or steel with a thin layer of zinc; being more reactive, the zinc is corroded in place of the iron and goes on protecting it even if the coating is scratched. (3) Electroplating with chromium or tin, or alloying iron with chromium and nickel to make stainless steel, which does not rust. OR (c)(ii) Aluminium lies above iron in the reactivity series, so it displaces iron from iron(III) oxide in a highly exothermic reaction (the thermit reaction). So much heat is released that the iron formed is **molten**; it runs into the crack in the rail or machine part and welds it on solidifying. ${\text{Fe}}_2{\text{O}}_3+2\text{Al}⟶2\text{Fe}+{\text{Al}}_2{\text{O}}_3+\text{heat}$

   Step-by-step solution →
6. Q266 CBSE 2023
   The melting points and the boiling points of ionic ​compounds are comparatively much higher than that of the covalent compounds. The ionic compounds are so called because they are formed by the transfer of electrons from a metal to a non-metal. In the ionic compounds, the transfer ​of electrons from one element ​to the other is ​controlled by their electronic configurations. It is because every element ​tends to attain a completely ​filled valence ​shell ​of its nearest noble gas or a stable octet.

   1. (a)The atomic number of sodium is $11$. Write its electronic configuration and state the number of electrons it can lose to have a stable octet.[1]
   2. (b)The atomic number of chlorine is $17$. Write its electronic configuration. Name the nearest noble gas whose octet chlorine will attain after gaining one electron.[1]
   3. (c)(i)Show the formation of MgO by the transfer of electrons. The atomic numbers of magnesium and oxygen are $12$ and $8$ respectively.[2]
   4. (c)(ii)OR : Write the symbols and names of the anion and the cation present in the aqueous solution of the following compounds : (I) Sodium chloride (II) Potassium nitrate[2]
   Show answer

   Sodium (2,8,1) loses one electron; chlorine gains one to attain argon's octet; magnesium transfers two electrons to oxygen to form MgO.

   (a) Sodium, $Z=11$, has the electronic configuration $2,8,1$. It can **lose one** electron to attain a stable octet, becoming ${\text{Na}}^{+}$ with the configuration $2,8$. (b) Chlorine, $Z=17$, has the electronic configuration $2,8,7$. On gaining one electron it becomes ${\text{Cl}}^{-}$ with $2,8,8$, which is the octet of **argon**. (c)(i) Magnesium, $Z=12$, is $2,8,2$ and oxygen, $Z=8$, is $2,6$. Magnesium loses its two outermost electrons and oxygen gains them: $\text{Mg}⟶{\text{Mg}}^{2+}+2e^{-}$ (now $2,8$) and $\text{O}+2e^{-}⟶{\text{O}}^{2-}$ (now $2,8$). The oppositely charged ions attract strongly, giving ${\text{Mg}}^{2+}+{\text{O}}^{2-}⟶\text{MgO}$. (c)(ii) OR — (I) In aqueous sodium chloride the cation is ${\text{Na}}^{+}$, the sodium ion, and the anion is ${\text{Cl}}^{-}$, the chloride ion. (II) In aqueous potassium nitrate the cation is ${\text{K}}^{+}$, the potassium ion, and the anion is ${\text{NO}}_3^{-}$, the nitrate ion.

   Step-by-step solution →
7. Q267 CBSE 2020
   The ​compound obtained ​on reaction of ​iron with steam is/are ​:

   1. (a)${\text{Fe}}_2{\text{O}}_3$
   2. (b)${\text{Fe}}_3{\text{O}}_4$
   3. (c)$\text{FeO}$
   4. (d)${\text{Fe}}_2{\text{O}}_3$ and ${\text{Fe}}_3{\text{O}}_4$
   Show answer

   (b) ${\text{Fe}}_3{\text{O}}_4$

   Step-by-step solution →
8. Q268 CBSE 2020
   Which ​one of ​the ​following statements is ​not ​correct ​?

   1. (a)Generally, all metal carbonates react with acids to give salt, water and carbon dioxide.
   2. (b)All metal oxides react with water to give salt and hydrogen gas.
   3. (c)Some of the metals react with acids to give salt and hydrogen gas.
   4. (d)Some non-metal oxides react with water to form acids.
   Show answer

   (b) All metal oxides react with water to give salt and hydrogen gas.

   Step-by-step solution →
9. Q269 CBSE 2020
   An element ​‘X’ reacts with ${\text{O}}_2$ to give ​a compound with a high melting ​point. This compound ​is ​also soluble in water. The ​element ‘X’ ​is likely to be ​:

   1. (a)iron
   2. (b)calcium
   3. (c)carbon
   4. (d)silicon
   Show answer

   (b) calcium

   Step-by-step solution →
10. Q270 CBSE 2020
    Copper utensils slowly lose ​their shiny brown surface ​and gain a ​green coat on prolonged exposure to atmospheric air. This ​is due ​to ​the formation of a ​coating ​of

    1. (a)Copper sulphate
    2. (b)Copper carbonate
    3. (c)Cupric oxide
    4. (d)Cuprous oxide
    Show answer

    (b) Copper carbonate

    Step-by-step solution →
11. Q271 CBSE 2020
    When steam ​is passed ​over ​red ​hot iron

    1. (a)No reaction takes place.
    2. (b)${\text{O}}_2$ and $\text{Fe}(\text{OH}{)}_3$ are formed.
    3. (c)${\text{H}}_2$ and ${\text{Fe}}_3{\text{O}}_4$ are formed.
    4. (d)${\text{H}}_2$ and ${\text{Fe}}_2{\text{O}}_3$ are formed.
    Show answer

    (c) ${\text{H}}_2$ and ${\text{Fe}}_3{\text{O}}_4$ are formed.

    Step-by-step solution →
12. Q272 CBSE 2020
    Which ​one ​of the ​following statements is ​true about the ​position ​of metals in the activity series ​of ​metals ?

    1. (a)Copper is below hydrogen but above lead.
    2. (b)Iron is below lead and zinc.
    3. (c)Zinc is below magnesium but above aluminium.
    4. (d)Magnesium is below calcium but above aluminium.
    Show answer

    (d) Magnesium is below calcium but above aluminium.

    Step-by-step solution →
13. Q273 CBSE 2020
    An ​element X with atomic number 12 forms a compound with element ​Y ​with ​atomic number ​17. ​The formula of ​the compound formed is

    1. (a)XY
    2. (b)${\text{XY}}_2$
    3. (c)${\text{X}}_2\text{Y}$
    4. (d)${\text{X}}_2{\text{Y}}_3$
    Show answer

    (b) ${\text{XY}}_2$

    Step-by-step solution →
14. Q274 CBSE 2020
    An ​element ‘X’ ​with atomic number 11 forms a ​compound with element ‘Y’ with ​atomic number ​8. The ​formula of the compound formed is

    1. (a)$\text{XY}$
    2. (b)${\text{X}}_2\text{Y}$
    3. (c)${\text{XY}}_2$
    4. (d)${\text{X}}_2{\text{Y}}_3$
    Show answer

    (b) ${\text{X}}_2\text{Y}$

    Step-by-step solution →
15. Q275 CBSE 2020
    Consider the following statements about ​an element ‘X’ with ​number ​of protons 13. (A) It forms ​amphoteric oxide (B) Its valency ​is ​three (C) The formula of ​its chloride is ${\text{XCl}}_3$ The correct statements(s) is/are

    1. (a)only (A)
    2. (b)only (B)
    3. (c)(A) and (C)
    4. (d)(A), (B) and (C)
    Show answer

    (d) (A), (B) and (C)

    Step-by-step solution →
16. Q276 CBSE 2020
    For question numbers 13 and ​14, two statements ​are ​given – one labelled ​as Assertion (A) ​and the other ​labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as ​given below :

    Assertion (A): The metals and alloys are good conductors of electricity.

    Reason (R): Bronze is an alloy of copper and tin and it is not a good conductor of electricity.

    1. (a)Both (A) and (R) are true and (R) is correct explanation of the assertion.
    2. (b)Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
    3. (c)(A) is true but (R) is false.
    4. (d)(A) is false but (R) is true.
    Show answer

    (d) (A) is false but (R) is true.

    Step-by-step solution →
17. Q277 CBSE 2020
    What ​is ​‘rusting’? ​Describe with a labelled diagram ​an activity to ​investigate the ​conditions ​under which iron ​rusts.
    Show answer

    Rusting is the slow corrosion of iron in moist air; the activity shows it needs both air and water.

    Rusting is the slow corrosion of iron in moist air: iron reacts with oxygen and water and gets coated with a brown, flaky substance, rust, which is hydrated iron(III) oxide, ${\text{Fe}}_2{\text{O}}_3\cdot x{\text{H}}_2\text{O}$. Activity (see the labelled diagram): place clean iron nails in three corked test tubes: A with ordinary water (air and water); B with boiled distilled water under a layer of oil (water, no air); C with anhydrous calcium chloride (dry air, no water). After a few days only the nail in A rusts, so iron rusts only when both air and water are present.

    Step-by-step solution →
18. Q278 CBSE 2020
    List ​three ​differentiating ​features ​between ​the ​processes of galvanisation ​and alloying.
    Show answer

    Galvanisation coats iron with zinc and leaves its properties unchanged; alloying mixes metals into a homogeneous mixture and changes properties.

    Any three of these differences: (1) Galvanisation: a thin layer of zinc is coated on iron or steel. Alloying: a metal is mixed with another metal or with a non-metal. (2) Galvanisation: the product is not a homogeneous mixture; the zinc stays on the surface. Alloying: the product is a homogeneous mixture. (3) Galvanisation: the physical properties of the metal do not change. Alloying: the physical properties of the metal change; steel, for example, is harder than iron. (4) Galvanisation: it works because of the reactivity of metals, zinc being more reactive than iron. Alloying: the reactivity of the metals plays no role. (5) Galvanisation: it only prevents rusting. Alloying: some alloys resist rusting, and alloys are also made for other advantages.

    Step-by-step solution →
19. Q279 CBSE 2020
    Compare ​in tabular form the ​reactivities of the ​following ​metals with ​cold and hot water ​:

    1. (a)Sodium
    2. (b)​Calcium
    3. (c)​Magnesium
    Show answer

    Sodium reacts violently with cold water, calcium less violently, magnesium only with hot water; reactivity falls from sodium to magnesium.

    Sodium. Cold water: reacts violently; so much heat is evolved that the hydrogen formed catches fire. Hot water: reacts even more violently, and more heat is evolved. Calcium. Cold water: reacts less violently than sodium; the heat evolved is not enough for the hydrogen to catch fire, and bubbles of hydrogen stick to the metal so that it floats. Hot water: reacts vigorously; bubbles of hydrogen stick to the metal and it floats on the water. Magnesium. Cold water: does not react. Hot water: reacts to form magnesium hydroxide and hydrogen; bubbles of hydrogen stick to its surface and it floats on the water. Reactivity with water: sodium > calcium > magnesium.

    Step-by-step solution →
20. Q280 CBSE 2020
    Draw ​a labelled diagram of ​the set-up of ​a ​circuit to ​show that metals ​are good conductors of ​electricity.
    Show answer

    The bulb glows when a metal is connected between A and B in the circuit, showing that metals are good conductors.

    Labelled diagram: a battery (two cells), a switch, a bulb and connecting wires joined in one closed loop, with a gap between two terminals A and B; the metal to be tested, for example a strip of iron, copper or aluminium, is clipped between A and B so that it completes the circuit. When the switch is closed the bulb glows, showing that electric current flows through the metal: metals are good conductors of electricity.

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