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 10 of 18

1. Q181 CBSE 2025
   Using ​flow ​chart, show the steps involved in the method ​of extraction of ​a ​metal ​of medium reactivity from its ore.
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   The ore is concentrated, converted to the oxide by roasting (sulphide) or calcination (carbonate), reduced with carbon, then refined.

   Flow chart: Ore of a metal of medium reactivity → Concentration of the ore (gangue removed) → Sulphide ore → Roasting (heated strongly in excess air), or Carbonate ore → Calcination (heated strongly in limited air) → Metal oxide → Reduction to metal (heated with a reducing agent such as carbon) → Metal → Refining (purification, usually electrolytic) → Pure metal. With zinc as the example: $2\text{ZnS}+3{\text{O}}_2\to 2\text{ZnO}+2{\text{SO}}_2$; ${\text{ZnCO}}_3\to \text{ZnO}+{\text{CO}}_2$; $\text{ZnO}+\text{C}\to \text{Zn}+\text{CO}$.

   Step-by-step solution →
2. Q182 CBSE 2025
   Write the ​electron-dot structures of

   1. (i)sodium, and ​
   2. (ii)oxygen. Using these structures, ​show the ​formation of sodium oxide. ​Mark the anion and cation present in this compound. (At. No. $-$ Sodium $=11$ ​and ​Oxygen $=8$)
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   Two Na atoms each give one electron to an O atom, forming two ${\text{Na}}^{+}$ cations and one ${\text{O}}^{2-}$ anion in ${\text{Na}}_2\text{O}$.

   Sodium ($Z=11$) is $2,8,1$, so its electron-dot structure is $\text{Na}$ with one dot; oxygen ($Z=8$) is $2,6$, so its structure is $\text{O}$ with six dots. Each of two sodium atoms transfers its single outer electron to one oxygen atom: $2\text{Na}+\text{O}⟶2{\text{Na}}^{+}+{\text{O}}^{2-}$, that is ${\text{Na}}_2\text{O}$. Every ion now has the stable octet $2,8$. The cation is the sodium ion ${\text{Na}}^{+}$ and the anion is the oxide ion ${\text{O}}^{2-}$.

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3. Q183 CBSE 2025
   Design an activity to ​show that metals are ​good conductors of ​heat ​and have high ​melting ​points.
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   Heat melts wax holding a pin at the wire's far end, but the wire stays solid: metals conduct heat and have high melting points.

   Apparatus: an aluminium or copper wire, an iron stand with a clamp, wax, a pin and a candle or spirit lamp. Procedure: clamp the wire horizontally so that one end is held and the rest is free, fix the pin to the free end with a small piece of wax, and heat the wire with the flame near the clamped end. Observation: after some time the wax melts and the pin falls off, while the wire itself does not melt. Conclusion: heat travelled along the wire from the heated end to the far end, so metals are good conductors of heat; and the flame that easily melted the wax could not melt the wire, so metals have high melting points.

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4. Q184 CBSE 2025
   Study the experimental set-up given in the ​figure and answer ​the following questions ​:

   1. (a)Identify these metals ​from the following which can be used as “metal sample” in the given set-up ​: Aluminium, Copper, Iron, ​Lead, Silver
   2. (b)Write balanced chemical ​equations for the reaction in each case.

   Show answer

   Aluminium and iron react with steam to give the metal oxide and hydrogen; copper, lead and silver do not.

   (a) Aluminium and iron. They react with steam to give the metal oxide and hydrogen gas, which is collected over water; copper, lead and silver do not react with water. (b) Aluminium: $2\text{Al(s)}+3{\text{H}}_2\text{O(g)}\to {\text{Al}}_2{\text{O}}_3\text{(s)}+3{\text{H}}_2\text{(g)}$ Iron: $3\text{Fe(s)}+4{\text{H}}_2\text{O(g)}\to {\text{Fe}}_3{\text{O}}_4\text{(s)}+4{\text{H}}_2\text{(g)}$

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5. Q185 CBSE 2025
   Two substances ‘A’ ​and ‘B’ are burnt in air separately. ​For ‘A’, ashes are collected and dissolved in water to get solution ​‘X’, while for ‘B’, fumes produced are passed through water to ​get solution ‘Y’. Both the solutions ‘X’ and ‘Y’ are then tested with pH ​paper.

   1. (a)If ‘X’ gives light blue colour and ‘Y’ gives orange colour to ​the pH paper, then write the nature and range ​of pH of ‘X’ and ‘Y’.
   2. (b)Which one of ​the two – A and B, is a metal ? Justify your answer.
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   X is basic (pH above 7) and Y is acidic (pH below 7); A is the metal because metal oxides are basic.

   (a) X is basic (alkaline) in nature: light blue on pH paper means a pH above $7$, roughly $8$ to $10$. Y is acidic in nature: orange means a pH below $7$, roughly $3$ to $4$. (b) A is the metal. The ash of A is its oxide, and it dissolves in water to give a basic solution, X; metal oxides are basic (apart from a few amphoteric ones such as aluminium oxide and zinc oxide), while the oxides of non-metals are generally acidic, which is why the fumes of B, a non-metal, give the acidic solution Y. For example, magnesium burns to give magnesium oxide, which forms magnesium hydroxide in water, while sulphur burns to give sulphur dioxide, which forms sulphurous acid.

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6. Q186 CBSE 2025
   Samples ​of four metals A, B, C ​and ​D were added one by one to the following solutions. The results obtained were tabulated as follows : Use the table above to answer the following ​questions ​about metals A, B, C and D :

   1. (i)Which is the least reactive metal?
   2. (ii)What would be ​observed if C is added to a solution of ​copper sulphate?
   3. (iii)Arrange the metals A, B, C and D in the ​order of their decreasing reactivity.

   Results of adding each metal to each solution

   Metal / Solution	Iron Sulphate	Copper Sulphate	Zinc Sulphate	Aluminium Sulphate
   A	–	Displacement	No reaction	No reaction
   B	Displacement	Displacement	Displacement	–
   C	Displacement	?	–	No reaction
   D	No reaction	No reaction	No reaction	No reaction

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   D is least reactive; C displaces copper from copper sulphate; the order is $\text{B}>\text{C}>\text{A}>\text{D}$.

   (i) D is the least reactive metal: it displaces none of iron, copper, zinc or aluminium from their sulphate solutions. (ii) C displaces copper from the copper sulphate solution: the blue colour of the solution fades and a reddish-brown coating of copper is deposited on C. C displaces iron, so it is more reactive than iron, which itself displaces copper. (iii) B > C > A > D (B is aluminium, C is zinc, A is iron, and D lies below copper).

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7. Q187 CBSE 2025
   Name and describe ​the ​most ​widely ​used method ​for ​refining impure ​metals ?
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   Electrolytic refining: the impure metal is the anode and pure metal the cathode in a salt solution; pure metal deposits on the cathode.

   The method is electrolytic refining. The impure metal is made the anode, connected to the positive terminal, and a thin strip of the pure metal is made the cathode, connected to the negative terminal; both dip into a solution of a salt of the metal, the electrolyte (for copper, acidified copper sulphate solution). When a current is passed, the metal of the anode dissolves into the electrolyte as ions ($\text{Cu}\to {\text{Cu}}^{2+}+2e^{-}$) and an equivalent amount of pure metal is deposited from the electrolyte on the cathode (${\text{Cu}}^{2+}+2e^{-}\to \text{Cu}$). Soluble impurities go into the solution, and insoluble impurities settle at the bottom of the anode as anode mud.

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8. Q188 CBSE 2025
   With ​the help ​of ​an ​activity, ​explain ​the conditions under ​which iron articles ​get rusted.
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   Iron rusts only when both air and water are present: only the nail in the tube with air and water rusts.

   Rusting of iron needs **both** air (oxygen) and water (moisture). In the activity, clean iron nails are kept in three corked test tubes: A contains ordinary water with air above it; B contains boiled distilled water sealed under a layer of oil (water but no air); C contains anhydrous calcium chloride (air but no moisture). After a few days only the nail in tube A is covered with rust, while those in B and C stay shiny. Hence iron articles rust only when air and water are both present: $4\text{Fe}+3{\text{O}}_2+2x{\text{H}}_2\text{O}\to 2{\text{Fe}}_2{\text{O}}_3\cdot x{\text{H}}_2\text{O}$ (rust).

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9. Q189 CBSE 2025
   Observe ​the following diagram showing an experiment to determine the conditions under which a metal ‘M’ corrodes. List your ​observations in each of the three cases A, B ​and C ​with reason, if the metal ​‘M’ is generally protected ​against corrosion by the method of galvanisation.

   Show answer

   M is iron; it rusts in tube A but not in B (oil) or C (dry air), so rusting needs both air and moisture.

   Metal ‘M’ is iron, because galvanisation (coating with zinc) is the method used to protect iron and steel. Tube A: the nail corrodes and a reddish-brown flaky layer of rust forms, because the tube holds moist air, so both water and oxygen reach the metal. Tube B: the nail does not corrode, because the oil covers it completely and keeps both air and moisture away from the metal surface. Tube C: the nail does not corrode, because the granules of drying agent at the bottom absorb the moisture and leave only dry air, so water is absent even though oxygen is present. Conclusion: both air (oxygen) and moisture are necessary together for iron to rust.

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10. Q190 CBSE 2025
    1. (i)Name two metals which react violently with cold water. List any three observations which a student ​notes when ​these metal are dropped ​in a ​beaker containing ​water.
    2. (ii)​Write a test to identify the ​gas evolved (if any) during the reaction of these metals with ​water.
    Show answer

    Potassium and sodium react violently with cold water, giving hydrogen, which burns with a pop sound near a burning splinter.

    (i) Potassium ($\text{K}$) and sodium ($\text{Na}$) react violently with cold water. Three observations: (1) the metal floats on the water and darts about rapidly on the surface with a hissing sound; (2) there is brisk effervescence — bubbles of a colourless gas (hydrogen) are given off; (3) so much heat is evolved that the hydrogen catches fire (with a lilac flame over potassium; sodium also melts into a shiny silvery ball); the liquid left behind turns red litmus blue. $2\text{Na}+2{\text{H}}_2\text{O}\to 2\text{NaOH}+{\text{H}}_2+\text{heat}$. (ii) The gas evolved is hydrogen. Collect it in a test tube and bring a burning splinter to the mouth of the tube: the gas burns with a pale blue flame and a characteristic 'pop' sound, which confirms hydrogen.

    Step-by-step solution →
11. Q191 CBSE 2025
    1. (a)​Show the formation of Aluminium Nitride (AlN) by the transfer of ​electrons. ​[ ​At. no. of Al = 13; At. no. of N = 7 ]
    2. (b)“Ionic compounds are solids ​and are generally brittle and break into ​pieces when pressure ​is applied.” Give reason to justify the statement.
    Show answer

    Al gives three electrons to N to form ${\text{Al}}^{3+}$ and ${\text{N}}^{3-}$, giving AlN; ionic solids are brittle because like charges repel when layers slip.

    (a) $\text{Al}(Z=13)$ has the arrangement $2,8,3$ and $\text{N}(Z=7)$ has $2,5$. Aluminium loses its three outermost electrons and nitrogen gains exactly those three: $\text{Al}(2,8,3)\to {\text{Al}}^{3+}(2,8)+3e^{-}$ and $\text{N}(2,5)+3e^{-}\to {\text{N}}^{3-}(2,8)$. Both ions now have the neon arrangement, and the strong electrostatic attraction between ${\text{Al}}^{3+}$ and ${\text{N}}^{3-}$, combined in the ratio $1:1$, gives aluminium nitride, $\text{AlN}$. (b) The ions in an ionic compound are packed in a regular three-dimensional lattice in which every ion is surrounded by ions of opposite charge, held by strong electrostatic forces; this makes the compound a hard solid. When pressure is applied, one layer slips over the next and ions of like charge come opposite each other; the strong repulsion between them pushes the layers apart and the crystal breaks along that plane, so ionic solids are brittle.

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12. Q192 CBSE 2025
    1. (i)Consider the following metals : K, Ca, Al, Cu, Ag, ​Fe Select from the above metals, a metal which I. ​does not react with oxygen even at high temperature. II. reacts with oxygen at ordinary temperature and forms a protective oxide layer which prevents the metal from further oxidation. III. catches fire when kept in the open. IV. does not burn in oxygen but ​the hot ​metal is ​coated with a black coloured oxide layer.
    2. (ii)What are amphoteric oxides ? With the ​help of balanced chemical ​equations show that aluminium oxide is an amphoteric ​oxide.
    3. (iii)What are alkalis ? Give one example.
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    Ag, Al, K and Cu match I to IV; amphoteric oxides react with both acids and bases, as ${\text{Al}}_2{\text{O}}_3$ does; alkalis are water-soluble bases.

    (i) I — Silver $(\text{Ag})$; II — Aluminium $(\text{Al})$; III — Potassium $(\text{K})$; IV — Copper $(\text{Cu})$. (ii) Amphoteric oxides are metal oxides that react with both acids and bases to produce a salt and water. Aluminium oxide does both: with an acid, ${\text{Al}}_2{\text{O}}_3+6\text{HCl}\to 2{\text{AlCl}}_3+3{\text{H}}_2\text{O}$, and with a base, ${\text{Al}}_2{\text{O}}_3+2\text{NaOH}\to 2{\text{NaAlO}}_2+{\text{H}}_2\text{O}$; hence it is amphoteric. (iii) Alkalis are bases that are soluble in water and give hydroxide ions in solution. Example: sodium hydroxide, $\text{NaOH}$ (potassium hydroxide and calcium hydroxide are others).

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13. Q193 CBSE 2025
    1. (i)With the help of balanced chemical equations state the process of extracting (I) mercury from its ore called cinnabar, and ​(II) copper from its ​sulphide ore.
    2. (ii)Silver and copper ​articles slowly lose ​their shiny surfaces when exposed to ​air. Name the compounds formed on ​(I) silver articles, and (II) ​copper articles in the ​form of coating.
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    Mercury comes from roasting then heating cinnabar, copper from self-reduction of ${\text{Cu}}_2\text{O}$ with ${\text{Cu}}_2\text{S}$; coatings are black silver sulphide and green basic copper carbonate.

    (i)(I) Mercury from cinnabar — two heatings. Cinnabar is first roasted in air, which converts the sulphide into mercury(II) oxide: $2\text{HgS}+3{\text{O}}_2\stackrel{\Delta }{\to }2\text{HgO}+2{\text{SO}}_2$. On heating further, the oxide itself is reduced to the metal: $2\text{HgO}\stackrel{\Delta }{\to }2\text{Hg}+{\text{O}}_2$. (I I) Copper from copper glance $({\text{Cu}}_2\text{S})$ — the ore is partly roasted in air, giving copper(I) oxide: $2{\text{Cu}}_2\text{S}+3{\text{O}}_2\stackrel{\Delta }{\to }2{\text{Cu}}_2\text{O}+2{\text{SO}}_2$. The oxide is then heated with the copper(I) sulphide left over, which reduces it to the metal: $2{\text{Cu}}_2\text{O}+{\text{Cu}}_2\text{S}\stackrel{\Delta }{\to }6\text{Cu}+{\text{SO}}_2$. (ii)(I) On silver articles: silver sulphide, ${\text{Ag}}_2\text{S}$ — a black coating formed with the hydrogen sulphide in the air. (I I) On copper articles: basic copper carbonate, ${\text{CuCO}}_3\cdot {\text{Cu(OH)}}_2$ — a green coating formed with moist carbon dioxide in the air.

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14. Q194 CBSE 2025
    The metals produced by various ​reduction processes are generally ​not very pure. ​They contain impurities of other ​metals and non-metals ​which must be removed to obtain pure metals. The most widely used process ​for refining metals such as gold, silver, zinc, copper, ​etc. is electrolytic refining.

    1. (a)What is the cathode and anode made of in the refining of silver by this process?[1]
    2. (b)Name the electrolyte used in this process and write its chemical formula.[1]
    3. (c)(i)What happens when an electric current is passed through the electrolyte?[2]
    4. (c)(ii)OR : You have two beakers A and B containing ferrous sulphate solution. If you dip a strip of aluminium in beaker A and a strip of copper in beaker B, what will be your observations after about three hours? Give reason for each of your observations.[2]
    Show answer

    Silver refining uses an impure silver anode, a pure silver cathode and silver nitrate; aluminium displaces iron from ferrous sulphate but copper does not.

    (a) The anode is a thick block (plate) of impure silver and the cathode is a thin strip (sheet) of pure silver. (b) The electrolyte is an aqueous solution of silver nitrate, ${\text{AgNO}}_3$ (acidified with a little dilute nitric acid). (c)(i) Silver from the anode dissolves into the electrolyte as ions, $\text{Ag}\to {\text{Ag}}^{+}+e^{-}$, and an equal amount of pure silver is deposited on the cathode, ${\text{Ag}}^{+}+e^{-}\to \text{Ag}$; soluble impurities pass into the solution while insoluble ones settle below the anode as anode mud. OR (c)(ii) In beaker A the aluminium strip becomes coated with a greyish-black deposit of iron and grows thinner, and the pale green colour of the solution fades to colourless, because aluminium is above iron in the reactivity series and displaces it: $2\text{Al}+3{\text{FeSO}}_4\to {\text{Al}}_2({\text{SO}}_4{)}_3+3\text{Fe}$. In beaker B there is no change at all - strip and pale green colour stay as they were - because copper is below iron in the reactivity series and cannot displace it.

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15. Q195 CBSE 2025
    Many pure ​metals ​like copper, iron and gold are very soft and as such are considered unsuitable for certain uses. Metallic objects around ​us ​such as cooking utensils, statues, ​ornaments, guns etc. are actually not made up of pure metals. Instead of pure metals, alloys are used in the ​design of most of the useful objects. Making alloys enhances the basic properties of a metal which is the primary constituent ​(metal) of an alloy.

    1. (I)How does electrical conductivity and melting point of a metal change when it is converted to its alloy by mixing a small amount of an element in it ?[1]
    2. (II)Name an alloy used for welding two wires together in an electric circuit. Write its major constituents.[1]
    3. (III)(a)What are alloys ? How is ‘Brass’ (an alloy) prepared ?[2]
    4. (III)(b)OR : What is stainless steel ? How is it prepared ? Write one important property which makes it more useful in making cooking utensils as compared to its primary metal.[2]
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    Alloying lowers conductivity and melting point; solder is lead and tin; brass is copper and zinc; stainless steel does not rust.

    (I) Both decrease: the electrical conductivity of the alloy is less than that of the pure metal, and so is its melting point. (II) Solder; its major constituents are lead (Pb) and tin (Sn), about half and half by mass. (III)(a) An alloy is a homogeneous mixture of two or more metals, or of a metal and a non-metal. Brass is made by melting copper and dissolving the required amount of zinc in the molten copper (about $70\%$ Cu and $30\%$ Zn), then cooling it. (III)(b) Stainless steel is an alloy of iron with chromium and nickel. It is made by melting iron and mixing in about $18\%$ chromium and $8\%$ nickel, then cooling. It does not rust or corrode, unlike pure iron, which is what makes it better for cooking utensils.

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16. Q196 CBSE 2025
    The metals produced by various reduction processes are not very pure. They ​contain impurities which ​must be ​removed ​to obtain pure metals. The ​most widely used process for refining impure metals is electrolytic refining. In ​this process chemical ​effect of electric ​current is used.

    1. (a)Name the materials used to make anode and cathode in the refining of copper by this process.
    2. (b)Name the salt of copper used as an electrolyte in this process and write its molecular formula.
    3. (c)(i)What happens when a steady current is passed through the electrolyte ? Name the part of the electrolytic cell where (1) pure copper is obtained and (2) impurities settle.
    4. (c)(ii)OR : How is copper obtained from its sulphide ? Write chemical equations involved in the process.
    Show answer

    Impure copper is the anode and pure copper the cathode in copper sulphate solution; impurities settle below the anode as anode mud.

    (a) The anode is a thick block of impure copper and the cathode is a thin strip of pure copper. (b) Copper sulphate, formula ${\text{CuSO}}_4$, used as an acidified aqueous solution. (c)(i) Copper from the impure anode dissolves into the solution as ${\text{Cu}}^{2+}$ ions and an equal amount of copper is deposited in the pure state on the cathode; (1) pure copper is obtained at the cathode and (2) the impurities settle below the anode as anode mud. (c)(ii) Part of the copper glance is roasted in air, $2{\text{Cu}}_2\text{S}+3{\text{O}}_2\to 2{\text{Cu}}_2\text{O}+2{\text{SO}}_2$, and the oxide so formed is then heated with the unroasted sulphide, $2{\text{Cu}}_2\text{O}+{\text{Cu}}_2\text{S}\to 6\text{Cu}+{\text{SO}}_2$, giving copper without any external reducing agent.

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17. Q197 CBSE 2024
    The ​number of ​shells required to write the electronic configuration ​of Potassium ​(At. No. 19)

    1. (a)1
    2. (b)2
    3. (c)3
    4. (d)4
    Show answer

    (d) 4

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18. Q198 CBSE 2024
    A ​metal and ​a non-metal ​that exists in liquid state at ​the room temperature are respectively ​:

    1. (a)Bromine and Mercury
    2. (b)Mercury and Iodine
    3. (c)Mercury and Bromine
    4. (d)Iodine and Mercury
    Show answer

    (c) Mercury and Bromine

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19. Q199 CBSE 2024
    The oxide ​which ​can react with $\text{HCl}$ as well ​as $\text{KOH}$ to give corresponding salt ​and ​water is

    1. (a)$\text{CuO}$
    2. (b)${\text{Al}}_2{\text{O}}_3$
    3. (c)${\text{Na}}_2\text{O}$
    4. (d)${\text{K}}_2\text{O}$
    Show answer

    (b) ${\text{Al}}_2{\text{O}}_3$

    Step-by-step solution →
20. Q200 CBSE 2024
    The metals which ​are ​found in both ​free ​state ​as well ​as combined ​state are :

    1. (a)Gold and platinum
    2. (b)Platinum and silver
    3. (c)Copper and silver
    4. (d)Gold and silver
    Show answer

    (c) Copper and silver

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