Case Based Questions Metals and Non-Metals - Science Class 10 PDF Download

Q1: Read the source below and answer the questions that follow:

A teacher demonstrated an experiment in class where she took different samples of iron, copper, sulfur, and graphite. She performed the following tests:

• Striking the samples with a hammer to test malleability.
• Drawing them into wires to check ductility.
• Testing their ability to conduct electricity by connecting them to a circuit.
• Observing their appearance before and after rubbing with sandpaper to check for metallic lustre.

(a) Identify which of the given substances are metals and non-metals based on tests done and also give observation table. (1 mark)
(b) From above samples which non-metal is a good conductor of electricity? (2 marks)
(c) Name two metals that are poor conductors of heat. (1 mark, )

Ans: 

(a) Iron and copper = Metals, Sulfur and graphite = Non-metals (based on malleability, ductility, and conductivity).

(b) Graphite is a good conductor of electricity because it has free-moving electrons in its layered structure.
(c) Lead and mercury are poor conductors of heat.

Q2: Read the source below and answer the questions that follow:

Riya conducted an experiment where she burned magnesium ribbon and sulfur powder in separate test tubes and dissolved the products in water. She then tested both solutions with red and blue litmus papers.

• Magnesium oxide turned red litmus blue.
• Sulfur dioxide turned blue litmus red.

(a) Identify the nature of the products formed when magnesium and sulfur burn in oxygen. (1 mark)
(b) Write the balanced chemical equations for both reactions. (2 marks)
(c) Name a metal oxide that shows both acidic and basic properties. (1 mark)
OR
(c) What happens when sodium is exposed to air? (1 mark)

Ans:
(a) Magnesium forms a basic oxide (magnesium oxide) and sulfur forms an acidic oxide (sulfur dioxide).
(b) Balanced equations:

• Magnesium: 2Mg + O₂ → 2MgO
• Sulfur: S + O₂ → SO₂

Q3: Read the source below and answer the questions that follow:

Aryan added sodium, calcium, and iron to separate beakers containing cold water. He observed that:

• Sodium reacted violently, producing heat and gas.
• Calcium reacted moderately, forming bubbles and a cloudy solution.
• Iron did not react with cold water.

(a) Identify the gases evolved in these reactions. (1 mark)
(b) Write the balanced equations for the reaction of sodium and calcium with water. (2 marks)
(c) Why does iron not react with cold water but react with steam? (1 mark)
OR
(c) Why is calcium stored in an air-tight container? (1 mark)

Ans:
(a) Hydrogen gas (H₂) is evolved in the reactions of sodium and calcium with water.
(b) Balanced equations:

• 2Na + 2H₂O → 2NaOH + H₂
• Ca + 2H₂O → Ca(OH)₂ + H₂

Q4: Read the source below and answer the questions that follow:

A student placed an iron nail in a beaker containing copper sulfate (CuSO₄) solution. After some time, he observed that the blue color faded, and a reddish-brown deposit appeared on the nail.

(a) Identify the reaction taking place. (1 mark)
(b) Write the balanced chemical equation for this reaction. (2 marks)
(c) What would happen if a copper wire was placed in iron sulfate (FeSO₄) solution? (1 mark)
OR
(c) Arrange the metals Fe, Cu, and Zn in order of reactivity. (1 mark)

Ans:
(a) This is a displacement reaction in which a more reactive metal (iron) displaces a less reactive metal (copper) from its salt solution.
(b) Balanced equation: Fe + CuSO₄ → FeSO₄ + Cu
(c) If a copper wire is placed in iron sulfate (FeSO₄) solution, no reaction will occur because copper is less reactive than iron and cannot displace iron from its salt.
OR
(c) Reactivity order: Zn > Fe > Cu.

Q5: Read the source below and answer the questions that follow:

A teacher demonstrated an experiment where she placed iron nails in three test tubes:

• Test Tube A: Contained only water.
• Test Tube B: Contained boiled distilled water with oil.
• Test Tube C: Contained anhydrous calcium chloride (dry air).

After a few days, the nails in Test Tube A rusted, but those in B and C did not.

(a) Identify the test tube in which iron nail will rust and state conditions required for rusting.  (1 mark)
(b) Write the balanced chemical equation for rusting of iron. (2 marks)
(c) Name one method to prevent rusting. (1 mark)
OR
(c) Why does oil prevent rusting? (1 mark)

Ans:
(a) The iron nail in Test Tube A will rust. Rusting requires both oxygen and water (moisture) together.
(b) Balanced equation:
4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ → Fe₂O₃·xH₂O (rust)
(c) One common method to prevent rusting is galvanisation (coating iron with zinc), which protects iron from corrosion.
OR
(c) Oil prevents rusting by forming a continuous protective layer on the metal surface that stops oxygen and water reaching the iron.

Q6: Read the source below and answer the questions that follow:

A chemistry teacher explained that metals lose electrons and non-metals gain electrons to form ionic bonds. She demonstrated this by showing the formation of sodium chloride (NaCl) where sodium donates an electron to chlorine.

(a) Identify which element is the electron donor and which is the electron acceptor in NaCl formation. (1 mark)
(b) Draw the electron dot structure for NaCl and explain why it is called an ionic bond. (2 marks)
(c) Why do ionic compounds have high melting and boiling points? (1 mark)
OR
(c) Why do ionic compounds conduct electricity in a molten or aqueous state? (1 mark)

Ans:
(a) Sodium (Na) is the electron donor and chlorine (Cl) is the electron acceptor.
(b) Electron dot structure (simple form):
Na• → :Cl••••••• → Na⁺ + Cl^-
Explanation: Sodium loses one electron to form Na⁺ and chlorine gains one electron to form Cl^-. The bond between Na⁺ and Cl^- is ionic because it is due to electrostatic attraction between oppositely charged ions.
(c) Ionic compounds have high melting and boiling points because strong electrostatic forces of attraction between oppositely charged ions require large amounts of energy to overcome.
OR
(c) Ionic compounds conduct electricity in molten or aqueous state because the ions are free to move and carry electric charge in those states.

Q7: Read the source below and answer the questions that follow:

A scientist demonstrated the electrolysis of molten aluminium oxide (Al₂O₃) in an industrial setup. Aluminium metal was collected at the cathode, while oxygen gas was released at the anode.

(a) Identify which electrode (cathode or anode) aluminium is deposited on. (1 mark)
(b) Write the reactions occurring at the cathode and anode. (2 marks)
(c) Name one more metal ores that can be refined using similar process? (1 mark)

Ans:
(a) Aluminium is deposited at the cathode (the negative electrode).
(b) Reactions:

• At cathode: Al³⁺ + 3e^- → Al
• At anode: 2O^2- → O₂ + 4e^-

Q8: Read the source below and answer the questions that follow:

During a factory visit, students observed the manufacturing of brass, stainless steel, and bronze. The guide explained that alloys are stronger and more resistant to corrosion than pure metals.

(a) Identify the main metals present in brass and stainless steel. (1 mark)
(b) What are alloys? Why alloy of gold is widely used instead of pure gold? (2 marks)
(c) What is alloy in which one of the metal is mercury called? (1 mark)
OR
(c) Why is aluminium used for making aircraft parts? (1 mark)

Ans:
(a) Brass is mainly an alloy of copper and zinc.
Stainless steel is mainly an alloy of iron with chromium (and often nickel and small amounts of carbon).
(b) An alloy is a homogeneous mixture of two or more elements, where at least one of them is a metal.
Pure gold (24 carat) is very soft and easily deforms, so it is alloyed with metals such as copper or silver to make it harder and more durable for use in jewellery and everyday items.
(c) An alloy in which one of the metals is mercury is called an amalgam.
OR
(c)Aluminium is used for aircraft parts because it is lightweight, has good strength-to-weight ratio, and is resistant to corrosion, which helps improve fuel efficiency and durability.

Q9: Read the source below and answer the questions that follow:

A ship's iron body was found to have rust patches, while the zinc-coated parts remained rust-free. The ship maintenance engineer explained that galvanization prevents rusting.

(a) Identify the chemical process causing rust formation. (1 mark)
(b) Write the balanced equation for the rusting of iron. (2 marks)
(c) What is the role of zinc in preventing rusting? (1 mark)
OR
(c) Name two other methods of rust prevention besides galvanization. (1 mark)

Ans:
(a) Rusting is an oxidation process in which iron reacts with oxygen and moisture to form hydrated iron(III) oxide (rust).
(b) Balanced equation:
4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ → Fe₂O₃·xH₂O (rust)
(c) Zinc provides protection in two ways: it forms a physical barrier coating over iron and it also acts as a sacrificial metal (zinc corrodes preferentially), protecting the iron even if the coating is scratched.
OR
(c) Two other methods to prevent rust are painting and oiling/greasing the metal surface; making alloys like stainless steel is another method.

Q10: Read the source below and answer the questions that follow:

Pratyush took sulfur powder on a spatula and heated it in a flame. He then collected the gas evolved by inverting a test tube over it. After the reaction, he took two strips of litmus paper (one dry and one moist) and exposed them to the collected gas. He observed that the dry litmus paper showed no change, while the moist litmus paper turned red.

(a) Identify the gas evolved and explain its effect on: (1 mark)
(i) Dry litmus paper
(ii) Moist litmus paper
(b) Write the balanced chemical equation for the reaction taking place. (2 marks)
(c) How does this experiment demonstrate the nature of the gas evolved? (1 mark)
OR
(c) Why does the gas turn moist litmus paper red but not affect dry litmus paper? (1 mark)

Ans:
(a) The gas evolved is sulfur dioxide (SO₂).
(i) Dry litmus paper: No visible change occurs because SO₂ does not ionise in the absence of water.
(ii) Moist litmus paper: Turns red because SO₂ dissolves in the water on the moist paper to form sulfurous acid, which releases H⁺ ions and makes the medium acidic.
(b) Balanced chemical equation:
S + O₂ → SO₂
(c) This experiment shows that SO₂ is an acidic oxide because it turns moist litmus red by forming an acidic solution (H₂SO₃) on dissolving in water.
OR
(c) SO₂ affects moist litmus paper because it reacts with water to form acid (sulfurous acid) which gives H⁺ ions; dry litmus paper is not affected because there is no water for SO₂ to dissolve in and form H⁺ ions.)