CBSE Board-Style Questions with Detailed Explanations — 1 Mark, 2 Marks, 3 Marks & 4 Marks
This page covers Chapter 3 – Metals and Non-Metals of Class 10 CBSE Science. This is one of the most scoring chapters in the board examination and is also extremely important for competitive exams like NTSE, Science Olympiad, and JEE Foundation. Questions from this chapter appear in almost every board paper.
You will find 15 carefully crafted, original questions across all mark categories — exactly following the CBSE board exam pattern. Every question comes with a detailed board-style explanation so you understand the concept deeply, not just the answer. Focus on understanding reactions and properties — these are often twisted in board papers.
Key Topics Covered in This Chapter:
Name the metal that is the best conductor of electricity and the non-metal that is also a good conductor of electricity.
Best conductor of electricity among metals: Silver (Ag)
Non-metal that conducts electricity: Graphite (an allotrope of Carbon)
Silver has the highest electrical conductivity of all metals, but copper is more commonly used in wiring because it is far cheaper while still being an excellent conductor. Among non-metals, graphite is unique — it has a layered structure where each carbon atom is bonded to three others, leaving one free electron per atom that can carry electric current. This makes graphite a good conductor, unlike most other non-metals.
What is an amalgam? Give one example.
An amalgam is an alloy in which one of the metals is mercury (Hg).
Example: Zinc amalgam (Zinc + Mercury) — used in dry cell batteries.
Amalgams are a special category of alloys. Sodium amalgam (Na-Hg) is used in some industrial chemical processes. Dental amalgam (silver, tin, copper with mercury) was historically used to fill tooth cavities. The key identification feature is always the presence of mercury as one of the components.
Arrange the following metals in decreasing order of reactivity: Iron, Sodium, Copper, Gold.
Decreasing order of reactivity: Sodium > Iron > Copper > Gold
The reactivity series ranks metals from most reactive (top) to least reactive (bottom). Sodium is highly reactive — it reacts violently even with cold water. Iron is moderately reactive and rusts slowly in moist air. Copper is low in reactivity and does not react with dilute acids. Gold is the least reactive metal (noble metal) — it does not corrode or tarnish at all, which is why it is used in jewellery and electronics.
Which property of metals allows them to be drawn into thin wires? Name one metal that shows this property to a very high degree.
The property that allows metals to be drawn into thin wires is called ductility.
Most ductile metal: Gold (Au) — 1 gram of gold can be drawn into a wire about 2 km long.
Don't confuse ductility with malleability. Malleability is the property of metals that allows them to be beaten into thin sheets (e.g., aluminium foil). Both are due to the metallic bonding — layers of metal atoms can slide over each other without breaking, unlike ionic or covalent solids that shatter.
What happens when sodium metal is dropped into water? Write the chemical equation and state why the piece of sodium catches fire during this reaction.
When sodium is added to water, it reacts vigorously to produce sodium hydroxide and hydrogen gas. The reaction is highly exothermic.
The piece of sodium catches fire because the reaction releases so much heat that the hydrogen gas produced immediately ignites. Sodium also melts into a silvery ball due to the intense heat generated.
Differentiate between roasting and calcination with one example of each. At what stage of metal extraction are these processes used?
Roasting: The process of heating a sulphide ore strongly in excess of air (oxygen) to convert it into its metal oxide.
Calcination: The process of heating a carbonate or hydroxide ore strongly in limited or absence of air to convert it into its metal oxide.
Both roasting and calcination are used during the concentration and conversion of ore stage — specifically to convert the ore into the metal oxide form, which can then be reduced to obtain the free metal.
Key Difference: Roasting uses excess air (for sulphide ores); Calcination uses limited/no air (for carbonate/hydroxide ores).
A student placed a clean iron nail in a solution of copper sulphate. After 30 minutes, the nail turned brown and the blue colour of the solution faded. Explain the reason for both observations with a chemical equation.
Iron is more reactive than copper. Iron displaces copper from copper sulphate solution. The displaced copper gets deposited on the surface of the iron nail, making it appear brown (reddish-brown colour of copper).
The blue colour of copper sulphate (CuSO₄) fades because Cu²⁺ ions are removed from the solution and replaced by Fe²⁺ ions. Iron(II) sulphate solution is pale green in colour, so the blue colour gradually disappears.
This is a displacement reaction — a more reactive metal (Fe) displaces a less reactive metal (Cu) from its salt solution. This is a direct demonstration of the reactivity series.
Why are most metals found in nature as ores and not in the free state? Name two metals that are found in the free (native) state in nature and give a reason.
Most metals are reactive and readily combine with elements present in nature — oxygen, sulphur, carbon dioxide, and water — to form compounds such as oxides, sulphides, and carbonates. These naturally occurring compounds of metals are called ores. Since most metals react with their surroundings over geological time, they are not found in the pure free state.
Metals found in free/native state:
Metals at the bottom of the reactivity series (Gold, Silver, Platinum) are least reactive and are found in nature in the free/native state. All other metals occur as compounds (ores).
What is the thermite reaction? Write the chemical equation and mention two practical applications of this reaction in daily life or industry.
The thermite reaction is a highly exothermic displacement reaction in which aluminium powder reacts with iron(III) oxide (Fe₂O₃) to produce molten iron and aluminium oxide. The temperature generated exceeds 2500°C.
Aluminium is higher in the reactivity series than iron, so Al can displace Fe from its oxide. This is a standard example of a displacement (or redox) reaction in CBSE Class 10.
Explain the process of electrolytic refining of copper. Draw a labelled diagram and mention what happens at the anode and cathode during the process.
Electrolytic Refining is the process of obtaining pure metal from impure metal using electrolysis.
Setup for Copper Refining:
The mass of the anode decreases while the mass of the cathode increases. The concentration of CuSO₄ solution remains approximately constant throughout. Precious metals collected in anode mud (gold, silver) are recovered separately, making refining economically valuable.
What is corrosion? Explain the conditions necessary for the rusting of iron. Write any two methods to prevent corrosion of metals.
Corrosion is the slow and gradual deterioration (damage) of a metal due to its chemical reaction with substances present in the environment, such as oxygen, moisture, acids, etc.
Conditions necessary for rusting of iron: Both oxygen (air) and water (moisture) must be present simultaneously. Iron does NOT rust in dry air or in pure water (without dissolved oxygen) alone.
Other methods include: electroplating, alloying, and using anti-corrosion coatings.
Explain how ionic compounds are formed using the example of magnesium oxide (MgO). Why do ionic compounds have high melting points and conduct electricity only in molten or aqueous state?
Magnesium (Mg) has 2 electrons in its outermost shell and loses both to achieve the noble gas configuration, forming Mg²⁺ ion.
Oxygen (O) has 6 electrons in its outermost shell and gains 2 electrons to achieve the noble gas configuration, forming O²⁻ ion.
The strong electrostatic force of attraction between Mg²⁺ and O²⁻ ions forms the ionic bond.
Ionic compounds exist as a large crystal lattice of positive and negative ions held together by very strong electrostatic forces. A large amount of energy is required to overcome these forces, hence they have high melting points.
In the solid state, ions are fixed at their lattice positions and cannot move — so no conduction. When melted or dissolved in water, the ions become free to move and carry electric current. Electricity is conducted by the movement of these free ions.
Describe in detail the general steps involved in the extraction of metals from their ores. How does the method of extraction depend on the position of the metal in the reactivity series? Give one example for each category.
(a) Metals low in reactivity series (e.g., Gold, Silver, Mercury):
Found in native state or as simple compounds. Extracted easily by heating alone.
Example: Mercury is obtained by heating cinnabar (HgS) in air:
(b) Metals in middle of reactivity series (e.g., Iron, Zinc, Copper):
Extracted by reduction of their oxides using carbon (coke) in a blast furnace.
Example: Iron from iron oxide:
(c) Metals high in reactivity series (e.g., Sodium, Calcium, Aluminium):
Cannot be reduced by carbon; extracted by electrolysis of their molten chlorides.
Example: Aluminium from molten Al₂O₃ (electrolysis — Hall-Héroult process).
Compare the physical and chemical properties of metals and non-metals under the following heads: (a) Physical state and lustre, (b) Conductivity, (c) Reaction with oxygen, (d) Nature of oxides formed. Give one example for each in the case of non-metals.
Metals: Almost all metals are solid at room temperature (exception: mercury is liquid). They have a shiny appearance called metallic lustre. They can be polished to maintain the shine.
Non-metals: Non-metals exist in all three states — solid (sulphur, carbon), liquid (bromine), and gas (oxygen, nitrogen). They generally have a dull appearance and lack lustre (exception: iodine has a slight lustre).
Metals: Good conductors of heat and electricity. Silver and copper are the best conductors.
Non-metals: Generally poor conductors (insulators) of heat and electricity. Exception: Graphite conducts electricity. Diamond is one of the best conductors of heat but not electricity.
Metals: React with oxygen to form basic metallic oxides.
Non-metals: React with oxygen to form acidic or neutral oxides.
Metal oxides: Basic in nature — they turn red litmus blue and react with acids to form salt and water.
Non-metal oxides: Acidic in nature — they turn blue litmus red and react with bases to form salt and water. Example: CO₂ + H₂O → H₂CO₃ (carbonic acid). Exception: Water (H₂O) is a neutral oxide of hydrogen.
Explain the following with chemical equations: (a) Why is aluminium more reactive than iron, yet aluminium articles do not corrode as easily as iron? (b) Why is copper not used to make cooking vessels even though it is a good conductor of heat? (c) What is the role of flux in the extraction of metals? (d) Why is sodium stored in kerosene?
Although aluminium is more reactive than iron, when aluminium is exposed to air, it reacts with oxygen to form a thin, hard, and tightly bonded layer of aluminium oxide (Al₂O₃) on its surface.
This oxide layer is non-porous and acts as a shield, preventing further reaction of the aluminium beneath with oxygen or moisture. Iron rust (Fe₂O₃), however, is porous and flaky — it does not stick tightly to the surface and keeps peeling off, exposing fresh iron to further corrosion.
Copper reacts with organic acids present in food (such as citric acid in lemons or tamarind) to form copper salts, which are toxic in nature. Consuming these copper compounds can cause serious health problems. Therefore, although copper is a good heat conductor, it is not safe for cooking acidic food. Aluminium and stainless steel are preferred.
During the extraction of metals (e.g., iron from a blast furnace), impurities like silica (SiO₂) or other gangue materials remain even after concentration of ore. A substance called flux is added that reacts with these impurities to form a fusible (easily melting) substance called slag, which can be easily separated from the molten metal.
Sodium is an extremely reactive metal. It reacts violently with oxygen, moisture, and even carbon dioxide present in air. To prevent these reactions and avoid fire hazards, sodium is stored submerged in kerosene oil. Kerosene does not react with sodium and acts as a protective medium keeping air and moisture away.