Metals & Non-metals CBQs — CBSE Class 10 (2027) with step-wise solutions

Sample Metals & Non-metals CBQs

1. Question 1MCQ1 mark
   Galvanisation is a process of coating iron articles with a layer of zinc to prevent the iron from rusting. The iron is protected even if the zinc coating is scratched and iron is exposed. Which of the following is true about how zinc prevents the rusting of iron? P) A galvanised iron article does not undergo oxidation. Q) The zinc coating prevents contact of iron with air. R) Zinc undergoes corrosion more easily than iron.
   • only P
   • only Q
   • only P and Q
   • only Q and R
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   1. [0.5 mark] Q correct: zinc coating blocks air/moisture from iron surface.
   2. [0.5 mark] R correct: zinc is more reactive than iron (sacrificial anode), so it corrodes preferentially. P false: oxidation still occurs but on zinc, not iron.

   Answer: (d) only Q and R

2. Question 2Assertion-Reason1 mark
   Assertion (A): Iodine is classified as a non-metal even though its crystals have a shining surface. Reason (R): Iodine crystals are brittle and do not conduct electricity, which are properties of non-metals.
   • (A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
   • (B) Both Assertion and Reason are true but Reason is NOT the correct explanation of Assertion.
   • (C) Assertion is true but Reason is false.
   • (D) Assertion is false but Reason is true.
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   1. [1 mark] (A) Both are true and R explains A: iodine is an exception that is lustrous, but its brittleness and inability to conduct electricity show it is a non-metal, so lustre alone does not decide the classification.

   Answer: (A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

3. Question 3Short answer3 marks
   Sakshi added iron filings to four test tubes A, B, C, D containing aqueous solutions of ZnSO4, CuSO4, FeSO4 and Al2(SO4)3 respectively. (a) In which test tube will she observe the reaction to be most vigorous? (b) What is the reason for her observation? (c) Write a well-balanced equation of the reaction in (b).
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   1. [1 mark] (a) Most vigorous reaction is in TEST TUBE B (CuSO4 solution).
   2. [1 mark] (b) Iron (Fe) is more reactive than copper (Cu) — Cu lies BELOW Fe in the reactivity series. Hence Fe displaces Cu from CuSO4. Fe cannot displace Zn or Al (more reactive than Fe), and FeSO4 has no displacement.
   3. [1 mark] (c) Balanced equation: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s). Blue colour of CuSO4 fades; reddish Cu deposits on iron filings.

   Answer: (a) Test tube B; (b) Cu < Fe in reactivity; (c) Fe + CuSO4 → FeSO4 + Cu.

4. Question 4Case study4 marks
   A piece of iron rusts when it comes in contact with air and moisture. Prakash had two identical shiny iron pieces P and Q. To prevent the pieces from rusting, he coated piece P with oil paint and he galvanized piece Q with a coat of zinc metal. He noticed that the coatings were not complete and that a small part of the iron was exposed in both the pieces. (i) What is Prakash likely to observe about the exposed part of piece P after some days? [1] (ii) What is he likely to observe about the exposed part of piece Q after some days? [1] (iii) Explain the reason for the difference in the two observations. [2]
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   1. [1 mark] (i) The exposed part of piece P gets rusted.
   2. [1 mark] (ii) The exposed part of piece Q does not get rusted.
   3. [1 mark] (iii) Oil paint prevents rusting only by preventing contact of iron with moist air, so the exposed iron of P rusts.
   4. [1 mark] (iii) In galvanising, zinc is more reactive than iron and gets oxidised in preference to iron, so even the exposed iron of Q is protected.

   Answer: P's exposed part rusts, Q's does not - paint is only a physical barrier, while zinc gives sacrificial protection.

5. Question 5Long answer5 marks
   Sabita, a science teacher in Koraput, is preparing a sample kit for her school. Each sample is kept in a sealed, labelled container. Her notes on six elements A to F are: A — lustrous; malleable; ductile; good conductor of electricity; melting point 1085 °C B — lustrous silvery liquid at room temperature; conducts electricity; freezes at −39 °C C — shiny violet-black crystals; brittle; does not conduct electricity D — grey-black, soft and slippery; conducts electricity; brittle E — soft enough to be cut with a knife; lustrous when freshly cut; melting point 98 °C F — yellow solid; brittle; does not conduct electricity; melting point 115 °C (a) Classify A to F as metals or non-metals. (1 mark) (b) Name the sample that breaks the general rule "metals are solids at room temperature" and the sample that breaks the rule "non-metals do not conduct electricity". (1 mark) (c) Which sample should be used for the connecting wires of a circuit kit? Give two reasons. (1 mark) (d) Why can sample D not be used for the connecting wires, even though it conducts electricity? Suggest one use for which D is suitable. (1 mark) (e) Using two pieces of information about E from the notes, explain why sample E would be unsuitable for making a spoon to stir boiling water. (1 mark)
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   1. [1 mark] (a) Metals: A, B and E (lustrous, conduct or are malleable); non-metals: C, D and F.
   2. [1 mark] (b) B breaks the first rule (a metal that is liquid at room temperature); D breaks the second (a non-metal that conducts electricity).
   3. [1 mark] (c) A, because it is ductile (can be drawn into wires) and is a good conductor of electricity.
   4. [1 mark] (d) D is brittle and not ductile, so it cannot be drawn into wires that bend; it is suitable as an electrode in a cell.
   5. [1 mark] (e) Two pieces of information: E is soft enough to be cut with a knife (the spoon would bend), and its melting point, 98 °C, is below 100 °C (it would melt in boiling water).

   Answer: (a) Metals: A, B, E; non-metals: C, D, F. (b) B (a liquid metal) and D (a conducting non-metal). (c) A, because it is ductile and a good conductor of electricity. (d) D is brittle and not ductile, so it cannot be drawn into bendable wire; it can be used as an electrode. (e) From the notes, E is soft enough to be cut with a knife, so the spoon would bend, and its melting point is 98 °C, below the 100 °C of boiling water, so it would melt.

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