CBSE Class 10 Science Chapter 3 Metals and Non-metals - In-Text Question Answer

 CBSE Class 10 Science Chapter 3 Metals and Non-metals - In-Text Question Answer

Q1	Give an example of a metal which- (i) is a liquid at room temperature. (ii) can be easily cut with a knife. (iii) is the best conductor of heat. (iv) is a poor conductor of heat.
Ans	(i) Mercury (Hg) is a metal that is in liquid form at room temperature. (ii) Sodium (Na) is a soft and highly reactive metal that can be easily cut with a knife. (iii) Silver (Ag) is known to be the best conductor of heat among all the metals. (iv) Bismuth (Bi), Mercury (Hg) and Lead (Pb) is a metal that is considered a poor conductor of heat compared to other metals.

Q2	Explain the meanings of malleable and ductile.
Ans	Malleable: The ability of a material to be easily shaped or flattened without breaking. Ductile: The ability of a material to be stretched into thin wires or filaments without breaking.

 

Q3	Why is sodium kept immersed in kerosene oil?
Ans	Sodium is kept immersed in kerosene oil to prevent it from reacting with air and moisture, which can be highly reactive and even lead to fires. Kerosene oil acts as a protective barrier, ensuring safety and preserving the purity of the sodium.

 

Q4

Write equations for the reactions of (i) iron with steam (ii) calcium and potassium with water

Ans

(i) Iron with Steam: Iron (Fe) reacts with steam (H2O) to form ferric ferrous oxide or magnetite (Fe3O4) and hydrogen gas (H2). Equation:  3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) (ii) Calcium and Potassium with Water: Calcium (Ca) and potassium (K) both react with water to produce their respective hydroxides and hydrogen gas. For calcium:  Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) For potassium:  2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)

 

Q5

Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.   Metal Iron(II) sulphate Copper (II) sulphate Zinc sulphate Silver nitrate A No reaction Displacement     B Displacement   No reaction   C No reaction No reaction No reaction Displacement D No reaction No reaction No reaction No reaction Use the Table above to answer the following questions about metals A, B, C and D. (i) Which is the most reactive metal? (ii) What would you observe if B is added to a solution of Copper(II) sulphate? (iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.

Ans

(i) Metal B is the most reactive metal because displacement reaction occurs which displaced iron from the solution. (ii) When metal B is added to a solution of Copper(II) sulfate a displacement reaction occurs and solution colour get changed. Metal B displace copper from the solution and make another compound. (iii) Metal B is the most reactive as it displaces iron. Metal A is less reactive, displacing copper. Metal C is less reactive, displacing only silver. Metal D is the least reactive, as it cannot displace any metal. So, the decreasing order of reactivity is B > A > C > D.

 

Q6	Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Ans	When dilute hydrochloric acid (HCl) is added to a reactive metal, hydrogen gas (H2) is produced. Its chemical reaction is as follow: Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)

 

Q7	What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Ans	When zinc (Zn) is added to a solution of iron (II) sulfate (FeSO4), I would observe a displacement reaction. Zinc is more reactive than iron, so it displaces iron from the solution and solution colour get chaged due to formation of zinc sulphate (ZnSO4). FeSO4 (aq) + Zn(s) → ZnSO4 (aq)+ Fe(s)

 

Q8

(i) Write the electron-dot structures for sodium and oxygen. (ii) Show the formation of Na2O and MgO by the transfer of electrons. (iii) What are the ions present in these compounds?

Ans

(i) Electron-Dot Structures for Sodium and Oxygen: Sodium (Na) has one valence electron, so its electron-dot structure is: Oxygen (O) has six valence electrons, so its electron-dot structure is: (ii) Formation of Na2O (Sodium Oxide): Sodium (Na) has one valence electron, and oxygen (O) has six valence electrons. Sodium (Na) loses one electron to become Na⁺, and oxygen (O) gains two electrons to become O²⁻. The transfer of electrons leads to the formation of the ionic compound Na₂O, where two sodium ions (Na⁺) combine with one oxygen ion (O²⁻). Formation of MgO (Magnesium Oxide): Magnesium (Mg) has two valence electrons and easily loses those two electrons to become Mg2+, and oxygen (O) gains two electrons to become O²⁻. The transfer of electrons leads in the formation of the ionic compound MgO, where one magnesium ion (Mg2+) combines with one oxygen ion (O²⁻). (iii) Ions Present in These Compounds: In Na2O (Sodium Oxide), the ions present are Na⁺ (sodium ions) and O²⁻ (oxygen ions). In MgO (Magnesium Oxide), the ions present are Mg2+ (magnesium ions) and O²⁻ (oxygen ions).

 

Q9	Why do ionic compounds have high melting points?
Ans	Ionic compounds have high melting points because they are held together by strong electrostatic attractions between oppositely charged ions in a three-dimensional lattice structure, and breaking these bonds requires a substantial amount of energy.

 

Q10

Define the following terms. (i) Mineral (ii) Ore (iii) Gangue

Ans

(i) A minerals are naturally occurring, inorganic solid substance with a specific chemical composition and a distinct crystalline structure generally found in earth’s crust. Example: potassium alums (K2SO4.Al2(SO4)3.24H2O), quartz, feldspar, and calcite. (ii) An ore is a naturally occurring mineral or rock from which a valuable or useful substance like metal, can be extracted profitably. Ores usually contain a higher concentration of the desired substance. Example: hematite (Fe2O3) is an ore of iron, while bauxite (Al2O3.2H2O) is an ore of aluminum and copper pyrite CuFeS2. (iii) Gangue are the impurities or waste material associated with the ore. Gangue are separated from ore during the process of extraction and refining.

 

Q11	Name two metals which are found in nature in the free state.
Ans	Metals which are found in nature in the free state are Gold and platinum.

 

Q12

What chemical process is used for obtaining a metal from its oxide?

Ans

The chemical process used for obtaining a metal from its oxide is "reduction". In this process, a metal oxide is combined with a reducing agent like- carbon, to remove oxygen and extract the pure metal. Example 1: Zinc oxide is reduced to metallic zinc by heating with carbon. ZnO + C → Zn + CO Example 2: Lead oxide is reduced to lead by heating with carbon PbO +C → Pb + CO Example 3: Iron oxide is reduced to lead by heating with carbon Fe2O3 + 3C → 2Fe + 3CO2

 

Q13	Metallic oxides of zinc, magnesium and copper were heated with the following metals. Metal Zinc Magnesium Copper Zinc oxide       Magnesium oxide       Copper oxide       In which cases will you find displacement reactions taking place?
Ans	In displacement reaction, a more reactive metal displaces a less reactive metal from its oxide. As per reactivity series; magnesium is the most reactive, zinc is less reactive and copper is the least reactive metal.  So, in this case, displacement reaction take place as fallow: Metal Zinc Magnesium Copper Zinc oxide - Displacement - Magnesium oxide - - - Copper oxide Displacement Displacement -

 

Q14	Which metals do not corrode easily?
Ans	The metals which are do not corrode easily are Gold and platinum.

 

Q15	What are alloys?
Ans	Alloys are homogeneous mixtures of two or more elements, where at least one of the components is a metal. Alloys are created by melting the primary metal and then dissolving the other elements into it in specific proportions.