Metals and Non Metals

Concept Required

A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its compound (usually a salt solution).

This is governed by the reactivity series of metals.

\[ \text{More reactive metal} + \text{Salt of less reactive metal} \rightarrow \text{New salt} + \text{Metal} \]

Solution Roadmap

• Step 1: Identify both metals in each option.
• Step 2: Compare their positions in the reactivity series.
• Step 3: Check if the free metal is more reactive than the metal in solution.
• Step 4: Conclude whether displacement occurs.

Step-by-Step Solution

Reactivity Series (relevant part):

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au

(a) \(\ce{NaCl}\) + Cu

Step 1: Metals involved → Na (in solution), Cu (free metal)

Step 2: Compare reactivity → Na is above Cu (more reactive)

Step 3: Cu cannot displace Na

Conclusion: No reaction

(b) \(\ce{MgCl2}\) + Al

Step 1: Metals → Mg (in solution), Al (free)

Step 2: Mg is above Al (more reactive)

Step 3: Al cannot displace Mg

Conclusion: No reaction

(c) \(\ce{FeSO4}\) + Ag

Step 1: Metals → Fe (in solution), Ag (free)

Step 2: Fe is above Ag

Step 3: Ag cannot displace Fe

Conclusion: No reaction

(d) \(\ce{AgNO3}\) + Cu

Step 1: Metals → Ag (in solution), Cu (free)

Step 2: Cu is above Ag (more reactive)

Step 3: Cu displaces Ag

Conclusion: Displacement occurs

\[ \ce{Cu + 2AgNO3 -> Cu(NO3)2 + 2Ag} \]

Final Answer

Only option (d) gives a displacement reaction.

Exam Importance

• Very frequently asked in CBSE Board Exams (1–2 marks direct).
• Concept used in reasoning-based MCQs in NTSE, Olympiads.
• Forms the base for corrosion, extraction of metals, and electrochemistry.
• Important for predicting feasibility of reactions in numerical chemistry.

Concept Required

Rusting is a chemical process in which iron reacts with oxygen and moisture to form hydrated iron(III) oxide.

\[ \ce{4Fe + 3O2 + xH2O -> 2Fe2O3.xH2O} \]

Rusting requires both oxygen and water. Preventing rusting involves blocking either or both.

Solution Roadmap

• Step 1: Identify conditions required for rusting.
• Step 2: Check whether each method blocks oxygen/moisture.
• Step 3: Evaluate effectiveness and practicality for a frying pan.
• Step 4: Conclude correct option.

Step-by-Step Solution

(a) Applying grease

Step 1: Grease forms a layer on iron.

Step 2: This layer blocks contact with air and moisture.

Step 3: Hence, rusting is prevented temporarily.

Valid method (short-term protection)

(b) Applying paint

Step 1: Paint forms a solid protective coating.

Step 2: It prevents oxygen and water from reaching iron.

Step 3: Hence, rusting is prevented.

Valid method (long-term protection)

(c) Applying a coating of zinc

Step 1: This process is called galvanisation.

Step 2: Zinc forms a barrier layer.

Step 3: Even if the layer is damaged, zinc reacts first (sacrificial protection).

\[ \text{Zn oxidizes before Fe, protecting iron} \]

Most effective method

(d) All of the above

Step 1: All methods prevent contact of iron with oxygen/moisture.

Step 2: Therefore, all help in preventing rusting.

Final Answer

(d) All of the above

Exam Importance

• Frequently asked conceptual MCQ in CBSE board exams.
• Very important for understanding corrosion and prevention techniques.
• Forms base for electrochemistry and metallurgy questions.
• Common in NTSE, Olympiad, and entrance exams as reasoning-based question.

Concept Required

Oxides of elements can be broadly classified as ionic or covalent.

• Ionic oxides → high melting point, often react with water to form soluble hydroxides
• Covalent oxides → may have high melting point but are generally insoluble in water

High melting point indicates strong bonding, usually ionic lattice or giant covalent structure.

Solution Roadmap

• Step 1: Identify type of oxide formed (ionic or covalent).
• Step 2: Check melting point behavior.
• Step 3: Check solubility in water.
• Step 4: Match both conditions simultaneously.

Step-by-Step Solution

Given Conditions:

• High melting point
• Soluble in water

Step 1: High melting point suggests ionic or giant covalent structure.

Step 2: Solubility in water suggests ionic compound forming hydroxide.

Step 3: Therefore, the oxide must be ionic in nature.

(a) Calcium

Step 1: Calcium forms calcium oxide:

\[ \ce{2Ca + O2 -> 2CaO} \]

Step 2: CaO is ionic and has high melting point.

Step 3: It reacts with water:

\[ \ce{CaO + H2O -> Ca(OH)2} \]

Satisfies both conditions

(b) Carbon

Forms \(\ce{CO2}\), which is molecular and has low melting point.

Rejected

(c) Silicon

Forms \(\ce{SiO2}\), which has high melting point but is insoluble.

Rejected

(d) Iron

Iron oxides have high melting point but are insoluble in water.

Rejected

Final Answer

(a) Calcium

Exam Importance

• Very important conceptual MCQ in CBSE board exams.
• Tests understanding of ionic vs covalent compounds.
• Common trap: students choose silicon due to high melting point but ignore solubility.
• Frequently appears in NTSE and Olympiad reasoning questions.

Concept Required

The metal used for coating food containers must be less reactive so that it does not react with food (especially acidic food).

More reactive metals can undergo chemical reactions with acids present in food:

\[ \text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{Hydrogen} \]

Such reactions can contaminate food and make it unsafe.

Solution Roadmap

• Step 1: Identify requirement → coating must be non-reactive.
• Step 2: Compare reactivity of zinc and tin.
• Step 3: Check which metal reacts with food acids.
• Step 4: Select correct reasoning.

Step-by-Step Solution

Step 1: Food items often contain acids (like citric acid, acetic acid).

Step 2: If coating metal is reactive, it will react with acids:

\[ \ce{Zn + 2HCl -> ZnCl2 + H2} \]

Step 3: Zinc is above tin in reactivity series → more reactive.

Step 4: Therefore, zinc can react with food and contaminate it.

Step 5: Tin is less reactive → safer for coating.

(a) Cost factor → Incorrect

(b) Melting point → Not relevant

(c) Zinc more reactive → Correct reason

(d) Zinc less reactive → Incorrect

Final Answer

(c) zinc is more reactive than tin

Exam Importance

• Very common CBSE board MCQ (direct concept-based).
• Tests real-life application of reactivity series.
• Important for corrosion, galvanisation, and food safety questions.
• Common trap: students choose melting point instead of reactivity.

Concept Required

Metals and non-metals can be distinguished based on physical and electrical properties such as malleability and electrical conductivity.

Experimental Roadmap

• Step 1: Perform mechanical test using hammer (malleability).
• Step 2: Perform electrical conductivity test using circuit.
• Step 3: Observe and record behavior.
• Step 4: Compare with known properties of metals/non-metals.

(a) Step-by-Step Procedure

Test 1: Malleability Test (Hammer)

Step 1: Place the sample on a hard surface.

Step 2: Gently strike it using the hammer.

Step 3: Observe the change in shape.

Observation:

• If the sample flattens → it is a metal
• If it breaks into pieces/powder → it is a non-metal

Test 2: Electrical Conductivity Test

Step 1: Connect battery, bulb, wires, and switch to form a circuit.

Step 2: Leave a gap in the circuit.

Step 3: Place the sample in the gap.

Step 4: Close the switch.

Observation:

• If bulb glows → sample conducts electricity → metal
• If bulb does not glow → poor conductor → non-metal

(b) Usefulness and Limitations

Usefulness:

• Simple and quick tests requiring basic equipment.
• Clearly demonstrate key properties of metals.
• Highly reliable for most common substances.

Limitations:

• Some metals like sodium are too soft to test safely.
• Graphite (a non-metal) conducts electricity → exception.
• Malleability test is not suitable for very small samples.

Conclusion

Combining both tests increases accuracy and helps correctly identify metals and non-metals in most cases.

Exam Importance

• Very important CBSE 3–5 mark descriptive question.
• Tests experimental understanding and reasoning.
• Frequently asked with “procedure + observation + conclusion”.
• Exception-based questions (graphite) are common in MCQs.

Concept Required

Amphoteric oxides are oxides that show both acidic and basic behaviour.

They react with:

• Acids → behave as base
• Bases → behave as acid

Understanding Roadmap

• Step 1: Identify oxide nature.
• Step 2: Check reaction with acids.
• Step 3: Check reaction with bases.
• Step 4: If both reactions occur → amphoteric.

Step-by-Step Explanation

Step 1: Amphoteric oxides possess dual nature.

Step 2: Reaction with acids:

They neutralize acids like a base.

Step 3: Reaction with bases:

They react with bases like an acid.

Step 4: Hence, they form salt and water in both cases.

Examples with Reactions

1. Aluminium oxide \(\ce{Al2O3}\)

With acid:

\[ \ce{Al2O3 + 6HCl -> 2AlCl3 + 3H2O} \]

With base:

\[ \ce{Al2O3 + 2NaOH -> 2NaAlO2 + H2O} \]

2. Zinc oxide \(\ce{ZnO}\)

With acid:

\[ \ce{ZnO + H2SO4 -> ZnSO4 + H2O} \]

With base:

\[ \ce{ZnO + 2NaOH -> Na2ZnO2 + H2O} \]

Conclusion

Amphoteric oxides react with both acids and bases. Common examples include \(\ce{Al2O3}\) and \(\ce{ZnO}\).

Exam Importance

• Very common 2–3 mark CBSE board question.
• Frequently asked in definition + example format.
• Important for MCQs involving oxide classification.
• Common trap: confusing amphoteric with basic oxides.

Concept Required

The ability of a metal to displace hydrogen from dilute acids depends on its position in the reactivity series.

Metals above hydrogen are more reactive and can displace hydrogen gas from acids.

General reaction:

\[ \text{Metal} + \text{Dilute Acid} \rightarrow \text{Salt} + \text{H}_2 \uparrow \]

Solution Roadmap

• Step 1: Identify metals above hydrogen.
• Step 2: Identify metals below hydrogen.
• Step 3: Write reactions for metals that displace hydrogen.
• Step 4: Conclude examples.

Step-by-Step Solution

Step 1: From reactivity series:

Metals like Zn, Fe lie above hydrogen → reactive.

Step 2: Metals like Cu, Ag lie below hydrogen → less reactive.

Step 3: Metals above hydrogen displace hydrogen:

Zinc:

\[ \ce{Zn + 2HCl -> ZnCl2 + H2} \]

Iron:

\[ \ce{Fe + H2SO4 -> FeSO4 + H2} \]

Step 4: Metals below hydrogen do not react:

• Copper (Cu) → No reaction
• Silver (Ag) → No reaction

Final Answer

Metals that displace hydrogen: Zinc (Zn), Iron (Fe)
Metals that do not: Copper (Cu), Silver (Ag)

Exam Importance

• Very common CBSE short answer (2–3 marks).
• Frequently converted into MCQs and assertion-reason questions.
• Important for understanding corrosion and electrochemical reactions.
• Common trap: students forget hydrogen reference point in reactivity series.

Concept Required

Electrolytic refining is a purification process in which an impure metal is purified using electrolysis.

The principle involves oxidation at the anode and reduction at the cathode.

Process Roadmap

• Step 1: Select impure metal as anode.
• Step 2: Use pure metal as cathode.
• Step 3: Use metal salt solution as electrolyte.
• Step 4: Pass electric current.
• Step 5: Observe metal transfer from anode to cathode.

Step-by-Step Explanation

Step 1: At Anode (Oxidation)

Impure metal loses electrons and forms ions:

\[ \ce{M -> M^{n+} + ne^-} \]

Impurities either dissolve or fall as anode mud.

Step 2: At Cathode (Reduction)

Metal ions gain electrons and deposit as pure metal:

\[ \ce{M^{n+} + ne^- -> M} \]

Step 3: Role of Electrolyte

Electrolyte contains soluble salt of metal M:

\[ \ce{MSO4 \ or \ MNO3} \]

It provides ions for continuous conduction.

Final Answer

• Anode: Impure metal M
• Cathode: Pure metal M (thin sheet)
• Electrolyte: Solution of a salt of metal M

Exam Importance

• Very important CBSE 3-mark question (diagram + explanation).
• Frequently asked in board exams and viva questions.
• Concept used in electroplating and metallurgy chapters.
• Common trap: students confuse anode and cathode roles.

Concept Required

Sulphur is a non-metal that forms an acidic oxide when burnt in air.

Acidic oxides show acidic behaviour only in the presence of water.

Solution Roadmap

• Step 1: Identify the gas formed on heating sulphur.
• Step 2: Check behaviour on dry litmus.
• Step 3: Check behaviour on moist litmus.
• Step 4: Write balanced reactions.

Step-by-Step Solution

Step 1: When sulphur burns in air, it reacts with oxygen to form sulphur dioxide gas.

\[ \ce{S + O2 -> SO2} \]

Step 2: Action on dry litmus paper

Dry litmus has no water.

SO₂ cannot form acid without water.

Result: No colour change

Step 3: Action on moist litmus paper

SO₂ dissolves in water present in moist litmus:

\[ \ce{SO2 + H2O -> H2SO3} \]

Sulphurous acid is acidic → turns blue litmus red.

Result: Blue litmus turns red

Final Answer

• Dry litmus → No change
• Moist blue litmus → Turns red
• Reaction: \(\ce{S + O2 -> SO2}\)

Exam Importance

• Very common CBSE 3-mark question (experiment-based).
• Tests concept of acidic oxides and role of moisture.
• Frequently asked in practical exams and viva.
• Common trap: students say dry litmus changes colour (incorrect).

Concept Required

Rusting is an electrochemical process in which iron reacts with oxygen and moisture to form hydrated iron(III) oxide.

\[ \ce{4Fe + 3O2 + xH2O -> 2Fe2O3.xH2O} \]

Rusting requires both oxygen and water.

Prevention Strategy Roadmap

• Step 1: Identify conditions required for rusting.
• Step 2: Block contact with air/moisture.
• Step 3: Use protective or sacrificial coating.
• Step 4: Apply suitable real-life method.

Step-by-Step Explanation

Method 1: Painting / Oiling / Greasing

Step 1: Apply a protective layer over iron.

Step 2: This layer prevents oxygen and moisture from reaching iron.

Step 3: Without air and water, rusting cannot occur.

Method 2: Galvanisation (Zinc Coating)

Step 1: Coat iron with zinc metal.

Step 2: Zinc acts as a physical barrier.

Step 3: Zinc is more reactive than iron, so it oxidizes first:

\[ \ce{Zn -> Zn^{2+} + 2e^-} \]

Step 4: This protects iron even if coating is damaged (sacrificial protection).

Final Answer

• Painting / applying oil or grease
• Galvanisation (coating with zinc)

Exam Importance

• Very common CBSE 2-mark direct question.
• Frequently appears in MCQs and case-based questions.
• Important for corrosion and electrochemistry concepts.
• Common trap: students write only one method or forget explanation.

Concept Required

Non-metals generally form acidic oxides when they react with oxygen.

These oxides show acidic nature because they form acids when dissolved in water.

Understanding Roadmap

• Step 1: Identify type of element (non-metal).
• Step 2: Observe nature of oxide formed.
• Step 3: Check reaction with water.
• Step 4: Conclude acidic behaviour.

Step-by-Step Explanation

Step 1: Non-metals react with oxygen to form covalent oxides.

Step 2: These oxides are generally acidic in nature.

Step 3: When dissolved in water, they form acids:

Example 1: Carbon dioxide

\[ \ce{CO2 + H2O -> H2CO3} \]

Example 2: Sulphur dioxide

\[ \ce{SO2 + H2O -> H2SO3} \]

Step 4: These acids turn blue litmus red, confirming acidic nature.

Final Answer

Non-metals form acidic oxides when they combine with oxygen.

Exam Importance

• Very common CBSE 1–2 mark direct question.
• Important for oxide classification (acidic/basic/amphoteric).
• Frequently used in MCQs and assertion-reason questions.
• Common trap: forgetting exceptions like neutral oxides (CO, NO).

Concept Required

The uses and extraction of metals depend on their reactivity, physical properties, and chemical stability.

Answering Roadmap

• Identify property → Link to behavior → Explain application
• For ores: Explain conversion step → justify ease of extraction

(a) Jewellery metals

Step 1: Gold, silver, platinum are very low in reactivity.

Step 2: They do not react with air, water, or chemicals.

Step 3: They are lustrous and highly malleable.

Conclusion: Suitable for jewellery due to shine and durability.

(b) Storage under oil

Step 1: Na, K, Li are highly reactive metals.

Step 2: They react violently with oxygen and moisture.

\[ \ce{2Na + 2H2O -> 2NaOH + H2} \]

Step 3: Reaction may produce heat → fire risk.

Conclusion: Stored under oil to prevent contact with air and water.

(c) Aluminium utensils

Step 1: Aluminium is reactive.

Step 2: It forms a stable oxide layer:

\[ \ce{4Al + 3O2 -> 2Al2O3} \]

Step 3: This layer prevents further corrosion.

Step 4: Aluminium is also a good conductor of heat.

Conclusion: Safe and efficient for cooking utensils.

(d) Ore conversion

Step 1: Metals are easier to extract from oxides.

Step 2: Carbonates → calcination:

\[ \ce{MCO3 -> MO + CO2} \]

Step 3: Sulphides → roasting:

\[ \ce{2MS + 3O2 -> 2MO + 2SO2} \]

Step 4: Oxides are reduced easily to metals.

Conclusion: Conversion improves extraction efficiency.

Final Summary

Each statement is explained based on reactivity, stability, and ease of extraction of metals.

Exam Importance

• Very important CBSE 4–5 mark long answer.
• Frequently appears as case-based or reasoning question.
• Tests conceptual clarity + real-life application.
• Common trap: writing properties without linking to reason.

Concept Required

Copper undergoes corrosion in moist air, forming a green layer of basic copper carbonate.

This layer is basic in nature and can be removed by acids through a neutralisation reaction.

Explanation Roadmap

• Step 1: Identify substance formed on copper (tarnish).
• Step 2: Identify nature of tarnish (basic).
• Step 3: Identify nature of cleaning agent (acidic).
• Step 4: Explain reaction and result.

Step-by-Step Explanation

Step 1: Copper reacts with air, moisture and carbon dioxide to form a green layer:

\[ \ce{2Cu + H2O + CO2 + O2 -> CuCO3.Cu(OH)2} \]

Step 2: This layer is basic in nature.

Step 3: Lemon/tamarind contain acids (citric acid, tartaric acid).

Step 4: Acid reacts with basic layer (neutralisation):

\[ \ce{CuCO3.Cu(OH)2 + 4H+ -> 2Cu^{2+} + CO2 + 3H2O} \]

Step 5: The green layer dissolves, exposing clean copper surface.

Final Answer

Sour substances clean copper because their acids react with and dissolve the basic green coating, restoring the shiny metal surface.

Exam Importance

• Very common CBSE 2–3 mark reasoning question.
• Tests corrosion + acid-base reaction concept.
• Frequently asked in case-based questions.
• Common trap: students forget to mention “basic copper carbonate”.

Concept Required

The chemical behaviour of metals and non-metals is primarily based on their tendency to lose or gain electrons.

Metals generally form positive ions (cations), whereas non-metals form negative ions (anions) or covalent bonds.

Comparison Roadmap

• Step 1: Compare electron behaviour (loss/gain).
• Step 2: Compare reactions with oxygen, water, and acids.
• Step 3: Compare displacement and redox behaviour.
• Step 4: Summarise differences in tabular form.

Conclusion

Metals are electropositive and form basic compounds, whereas non-metals are electronegative and form acidic compounds.

Exam Importance

• Very important CBSE 4–5 mark question (table format preferred).
• Frequently appears in case-based and MCQ format.
• Key foundation for chemical bonding and reactions.
• Common trap: writing physical properties instead of chemical ones.

Concept Required

Gold is a noble metal and does not react with most acids. However, it dissolves in a special mixture called aqua regia.

Aqua regia is a mixture of concentrated acids:

\[ \text{Aqua regia} = \ce{HCl} + \ce{HNO3} \; (3:1) \]

Detective Reasoning Roadmap

• Step 1: Observe → shine increased
• Step 2: Observe → weight decreased
• Step 3: Infer → metal removed, not just cleaned
• Step 4: Identify chemical capable of dissolving gold

Step-by-Step Explanation

Step 1: The bangles became shiny → surface layer removed.

Step 2: Weight decreased → actual metal was dissolved.

Step 3: Ordinary acids cannot dissolve gold.

Step 4: Only aqua regia can dissolve gold:

\[ \ce{Au + 3HNO3 + 4HCl -> HAuCl4 + 3NO2 + 3H2O} \]

Step 5: Hence, part of gold itself dissolved → weight loss.

Step 6: Fresh surface exposed → appears shiny.

Final Answer

The solution used was aqua regia, which dissolved a layer of gold, making the bangles shiny but reducing their weight.

Exam Importance

• Very important CBSE case-based question.
• Tests concept of noble metals and aqua regia.
• Frequently appears in reasoning-based MCQs.
• Common trap: writing “acid removes impurities” instead of “gold dissolves”.

Concept Required

The choice of material for hot water tanks depends mainly on reactivity with water and resistance to corrosion.

Reasoning Roadmap

• Step 1: Check reactivity of metal with hot water.
• Step 2: Check corrosion (rusting) tendency.
• Step 3: Compare suitability for long-term use.

Step-by-Step Explanation

Step 1: Behaviour of Copper

• Copper is a less reactive metal.
• It does not react with water, even at high temperature.
• It resists corrosion and remains stable.

Step 2: Behaviour of Iron (Steel)

• Iron is more reactive than copper.
• It reacts with oxygen and moisture to form rust:

\[ \ce{4Fe + 3O2 + xH2O -> 2Fe2O3.xH2O} \]

• Hot water accelerates rusting.
• This weakens the tank over time.

Step 3: Comparison

Final Answer

Copper is used because it does not react with hot water and resists corrosion, whereas steel rusts in the presence of water and air, making it unsuitable for hot water tanks.

Exam Importance

• Frequently asked CBSE 2–3 mark reasoning question.
• Tests understanding of reactivity series and corrosion.
• Expected answer: non-reactivity + rusting of iron (keep it precise).
• Common mistake: writing thermal conductivity instead of chemical reason.