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Class 10th Chapter 3 Metal and Non- Metal Notes for Exam

Corrosion

Alloys

Alloys are homogeneous mixtures of metal with other metals or nonmetals. Alloy formation enhances the desirable properties of the material, such as hardness, tensile strength and resistance to corrosion.
Examples of a few alloys –
Brass: copper and zinc
Bronze: copper and tin
Solder: lead and tin
Amalgam: mercury and other metal

Corrosion

Gradual deterioration of material usually a metal by the action of moisture, air or chemicals in the surrounding environment.
Rusting:
4Fe(s)+3O2(from air)+xH2O(moisture)→2Fe2O3xH2O(rust)

Corrosion of copper:
Cu(s)+H2O(moisture)+CO2(from air)→CuCO3.Cu(OH)2(green)

Corrosion of silver:
Ag(s)+H2S(from air)→Ag2S(black)+H2(g)

Prevention of Corrosion

Prevention:

1. Coating with paints or oil or grease: Application of paint or oil or grease on metal surfaces keep out air and moisture.

2. Alloying: Alloyed metal is more resistant to corrosion. Example: stainless steel.

3. Galvanization: This is a process of coating molten zinc on iron articles. Zinc forms a protective layer and prevents corrosion.

4. Electroplating: It is a method of coating one metal with another by the use of electric current. This method not only lends protection but also enhances the metallic appearance.
Example: silver plating, nickel plating.

5. Sacrificial protection: Magnesium is more reactive than iron. When it is coated on the articles made of iron or steel, it acts as the cathode, undergoes reaction (sacrifice) instead of iron and protects the articles.

Physical Properties

Physical Properties of Metals

● Hard and have a high tensile strength
● Solid at room temperature
● Sonorous
● Good conductors of heat and electricity
● Malleable, i.e., can be beaten into thin sheets
● Ductile, i.e., can be drawn into thin wires
● High melting and boiling points (except Caesium (Cs) and Gallium (Ga))
● Dense, (except alkali metals). Osmium – highest density and lithium – least density
● Lustrous
● Silver-grey in colour, (except gold and copper)

Non-Metals

Nonmetals are those elements which do not exhibit the properties of metals.

Physical Properties of Nonmetals

  • Occur as solids, liquids and gases at room temperature
  • Brittle
  • Non-malleable
  • Non-ductile
  • Non-sonorous
  • Bad conductors of heat and electricity

Exceptions in Physical Properties

  • Alkali metals (Na, K, Li) can be cut using a knife.
  • Mercury is a liquid metal.
  • Lead and mercury are poor conductors of heat.
  • Mercury expands significantly for the slightest change in temperature.
  • Gallium and caesium have a very low melting point.
  • Iodine is non-metal but it has lustre.
  • Graphite conducts electricity.
  • Diamond conducts heat and has a very high melting point.

Chemical Properties

Chemical Properties of Metals

● Alkali metals (Li, Na, K, etc) react vigorously with water and oxygen or air.
● Mg reacts with hot water.
● Al, Fe and Zn react with steam.
● Cu, Ag, Pt, Au do not react with water or dilute acids.

Reaction of Metals with Oxygen (Burnt in Air)

Metal + Oxygen→ Metal oxide (basic)
● Na and K are kept immersed in kerosene oil as they react vigorously with air and catch fire.
4K(s)+O2(g)→2K2O(s) (vigorous reaction)
● Mg, Al, Zn, Pb react slowly with air and form a protective layer that prevents corrosion.
2Mg(s)+O2(g)→2MgO(s) (Mg burns with white dazzling light)
4Al(s)+3O2(g)→2Al2O3(s)
● Silver, platinum and gold don’t burn or react with air.

Basic Oxides of Metals

Some metallic oxides get dissolved in water and form alkalis. Their aqueous solution turns red litmus blue.

Na2O(s)+H2O(l)→2NaOH(aq)
K2O(s)+H2O(l)→2KOH(aq)

Amphoteric Oxides of Metals

Amphoteric oxides are metal oxides which react with both acids as well as bases to form salt and water.
For example – Al2O3,ZnO,PbO,SnO
Al2O3(s)+6HCl(aq)→2AlCl3(aq)+3H2O(l)
Al2O3(s)+2NaOH(aq)→2NaAlO2(aq)+H2O(l)
ZnO(s)+2HCl(aq)→ZnCl2(aq)+H2O(l)
ZnO(s)+2NaOH(aq)→Na2ZnO2(aq)+H2O(l)

Reactivity Series

The below table illustrates the reactivity of metals from high order to low order.

Symbol              Element
KPotassium ( Highly Active Metal)
BaBarium
CaCalcium
NaSodium
MgMagnesium
AlAluminium
ZnZinc
FeIron
NiNickel
SnTin
PbLead
HHydrogen
CuCopper
HgMercury
AgSilver
AuGold
PtPlatinum
Metal and Non-Metal

Reaction of Metals with Water or Steam

Metal+Water→Metalhydroxide or Metaloxide+Hydrogen

2Na+2H2O(cold)→2NaOH+H2+heat
Ca+2H2O(cold)→Ca(OH)2+H2
Mg+2H2O(hot)→Mg(OH)2+H2
2Al+3H2O(steam)→Al2O3+3H2
Zn+H2O(steam)→ZnO+H2
3Fe+4H2O(steam)→Fe3O4+4H2

Reaction of Metals with Acid

Metal+diluteacid→Salt+Hydrogengas
2Na(s)+2HCl(dilute)→2NaCl(aq)+H2(g)
2K(s)+H2SO4(dilute)→K2SO4(aq)+H2(g)

Only Mg and Mn, react with very dilute nitric acid to liberate hydrogen gas.
Mg(s)+2HNO3(dilute)→Mg(NO3)2(aq)+H2(g)
Mn(s)+2HNO3(dilute)→Mn(NO3)2(aq)+H2(g)

Displacement Reaction

A more reactive element displaces a less reactive element from its compound or solution.

How Do Metals React with Solution of Other Metal Salts

Metal A+Salt of metal B → Salt of metal A + Metal B

Fe(s)+CuSO4(aq)→FeSO4(aq)+Cu(s)
Cu(s)+2AgNO3(aq)→Cu(NO3)(aq)+2Ag(s)

Reaction of Metals with Bases

Base+metal → salt+hydrogen
2NaOH(aq)+Zn(s) → Na2ZnO2(aq)+H2(g)
2NaOH(aq)+2Al(s)+2H2O(l) → 2NaAlO2(aq)+2H2(g)

Extraction of Metals and Non-Metals

Applications of Displacement Reaction

Uses of displacement reaction

  1. Extraction of metals
  2. Manufacturing of steel
  3. Thermite reaction: Al(s)+Fe2O3(s) → Al2O3+Fe(molten)

The thermite reaction is used in welding of railway tracks, cracked machine parts, etc.

Occurrence of Metals

Most of the elements, especially metals occur in nature in the combined state with other elements. All these compounds of metals are known as minerals. But out of them, only a few are viable sources of that metal. Such sources are called ores.
Au, Pt – exist in the native or free state.

Extraction of Metals

Metal and Non-Metal

Metals of high reactivity – Na, K, Mg, Al.
Metals of medium reactivity – Fe, Zn, Pb, Sn.
Metals of low reactivity – Cu, Ag, Hg

Roasting

Converts sulphide ores into oxides on heating strongly in the presence of excess air.
It also removes volatile impurities.
2ZnS(s)+3O2(g)+Heat→2ZnO(s)+2SO2(g)

Calcination

Converts carbonate and hydrated ores into oxides on heating strongly in the presence of limited air. It also removes volatile impurities.

ZnCO3(s)+heat→ZnO(s)+CO2(g)
CaCO3(s)+heat→CaO(s)+CO2(g)
Al2O3.2H2O(s)+heat→2Al2O3(s)+2H2O(l)
2Fe2O3.3H2O(s)+heat→2Fe2O3(s)+3H2O(l)

Extracting Metals Low in Reactivity Series

By self-reduction- when the sulphide ores of less electropositive metals like Hg, Pb, Cu etc., are heated in air, a part of the ore gets converted to oxide which then reacts with the remaining sulphide ore to give the crude metal and sulphur dioxide. In this process, no external reducing agent is used.

1. 2HgS(Cinnabar)+3O2(g)+heat→2HgO(crude metal)+2SO2(g)
2HgO(s)+heat→2Hg(l)+O2(g)

2. Cu2S(Copperpyrite)+3O2(g)+heat→2Cu2O(s)+2SO2(g)
2Cu2O(s)+Cu2S(s)+heat→6Cu(crude metal)+SO2(g)

3. 2PbS(Galena)+3O2(g)+heat→2PbO(s)+2SO2(g)
PbS(s)+2PbO(s)→2Pb(crudemetal)+SO2(g)

Extracting Metals in the Middle of Reactivity Series

Smelting – it involves heating the roasted or calcined ore (metal oxide) to a high temperature with a suitable reducing agent. The crude metal is obtained in its molten state.
Fe2O3+3C(coke)→2Fe+3CO2

Aluminothermic reaction – also known as the Goldschmidt reaction is a highly exothermic reaction in which metal oxides usually of Fe and Cr are heated to a high temperature with aluminium.
Fe2O3+2Al→Al2O3+2Fe+heat
Cr2O3+2Al→Al2O3+2Cr+heat

Extraction of Metals Towards the Top of the Reactivity Series

Electrolytic reduction:

1. Down’s process: Molten NaCl is electrolysed in a special apparatus.

At the cathode (reduction):
Na+(molten)+e→Na(s)
Metal is deposited.

At the anode (oxidation):
2Cl(molten)→Cl2(g)+2e
Chlorine gas is liberated.

2. Hall’s process: Mixture of molten alumina and a fluoride solvent usually cryolite, (Na3AlF6) is electrolysed.

At the cathode (reduction):
2Al3++6e→ 2Al(s)
Metal is deposited.

At the anode (oxidation):
6O2– → 3O2(g)+12e
Oxygen gas is liberated.

Enrichment of Ores

It means the removal of impurities or gangue from ore, through various physical and chemical processes. The technique used for a particular ore depends on the difference in the properties of the ore and the gangue.

Refining of Metals

Refining of metals – removing impurities or gangue from crude metal. It is the last step in metallurgy and is based on the difference between the properties of metal and the gangue.

Electrolytic Refining

Metals like copper, zinc, nickel, silver, tin, gold etc., are refined electrolytically.
Anode: impure or crude metal
Cathode: a thin strip of pure metal
Electrolyte: aqueous solution of metal salt

From anode (oxidation): metal ions are released into the solution
At cathode (reduction): the equivalent amount of metal from solution is deposited
Impurities deposit at the bottom of the anode.

The Why Questions

Electronic Configuration

Group 1 elements – Alkali metals

ElementElectronic Configuration 
Lithium(Li)2,1
Sodium(Na)2,8,1
Potassium(K)2,8,8,1
Rubidium(Rb)2,8,18,8,1
Metal and Non-Metal

Group 2 elements – Alkaline earth metals

ElementElectronic Configuration 
Beryllium(Be)2,2
Magnesium(Mg)2,8,2
Calcium(Ca)2,8,8,2
Stronium(Sr)2,8,18,8,2
Metal and Non-Metal

How Do Metals and Nonmetals React

Metals lose valence electron(s) and form cations.
Non-metals gain those electrons in their valence shell and form anions.
The cation and the anion are attracted to each other by strong electrostatic force, thus forming an ionic bond.
For example: In calcium chloride, the ionic bond is formed by opposite charged calcium and chloride ions.
Calcium atom loses 2 electrons and attains the electronic configuration of the nearest noble gas (Ar). By doing so, it gains a net charge of +2.

Metal and Non-Metal

The two Chlorine atoms take one electron each, thus gaining a charge of -1 (each) and attain the electronic configuration of the nearest noble gas (Ar).

Metal and Non-Metal

Ionic Compounds

The electrostatic attractions between the opposite charged ions hold the compound together.
Example: MgCl2, CaO, MgO, NaCl etc.

Properties of Ionic Compound

Ionic compounds

  1. Are usually crystalline solids (made of ions).
  2. Have high melting and boiling points.
  3. Conduct electricity when in aqueous solution and when melted.
  4. Are mostly soluble in water and polar solvents.

Physical Nature

Ionic solids usually exist in regular, well-defined crystal structures.

Electric Conduction of Ionic Compounds

Ionic compounds conduct electricity in the molten or aqueous state when ions become free and act as charge carriers.
In solid form, ions are strongly held by electrostatic forces of attractions and are not free to move; hence do not conduct electricity.

Metal and Non-Metal
Metal and Non-Metal

For example, ionic compounds such as NaCl does not conduct electricity when solid but when dissolved in water or in a molten state, it will conduct electricity.

Metal and Non-Metal

Melting and Boiling Points of Ionic Compounds

In ionic compounds, the strong electrostatic forces between ions require a high amount of energy to break. Thus, the melting point and boiling point of an ionic compound are usually very high.

Solubility of Ionic Compounds

Metal and Non-Metal

Most ionic compounds are soluble in water due to the separation of ions by water. This occurs due to the polar nature of water.
For example, NaCl is a 3-D salt crystal composed of Na+ and Cl ions bound together through electrostatic forces of attractions. When a crystal of NaCl comes into contact with water, the partial positively charged ends of water molecules interact with the Cl ions, while the negatively charged end of the water molecules interacts with the Na+ ions. This ion-dipole interaction between ions and water molecules assist in the breaking of the strong electrostatic forces of attractions within the crystal and ultimately in the solubility of the crystal.

Metal and Non-Metal

Access Answers of Science NCERT class 10 Chapter 3 – Metals and Non-metals ( All In text and Exercise Questions Solved)

In-text questions set 1 Page number 40 (Metals and Non-Metals)

1. 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?

Solution:

(i) Mercury is the metal which is liquid at room temperature

(ii) Sodium and potassium are the metals which can be cut with a knife

(iii) Silver is the best conductor of heat

(iv) Mercury is poor conductor of heat.

2. Explain the meanings of malleable and ductile.

Solution:

  1. Metals which can be beaten to sheets are said to be malleable
  2. Metals which can be drawn into thin wires are said to be ductile

In-text questions set 2 Page number 46 (Metals and Non-Metals)

1. Why is sodium kept immersed in kerosene oil?

Solution: Sodium is a reactive metals, if kept open it will react with oxygen to explore and catch fire. Sodium metal is kept immersed in kerosene to prevent their reaction with oxygen, moisture and carbon dioxide of air.

2. Write equations for the reactions of

(i) iron with steam

(ii) calcium and potassium with water

Solution: (i) Iron reacts with steam to form a magnetic oxide of Fe with the liberation of H2.

3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

(ii) Calcium reacts with water to form calcium hydroxide and hydrogen.

Ca(s) + 2H2O(I) → Ca(OH)2(aq) + H2(g)

Potassium reacts with cold water violently immediately with evolution of H2 which catches fire.

2K(s) + 2H2O(I) → 2KOH(aq) + 2H2(g)

3. 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

MetalIron(II) sulphateCopper(II) sulphateZinc sulphateSilver Nitrate
ANo reactionDisplacement
BDisplacement
CNo reactionNo reactionNo reactionDisplacement
DNo reactionNo reactionNo reactionNo reaction
Metal and Non-Metal

Use the Table above to answer the following questions about metals A, B, C and D.

  1. Which is the most reactive metal?
  2. What would you observe if B is added to a solution of Copper (II) sulphate?
  3. Arrange the metals A, B, C and D in the order of decreasing reactivity.

Solution:

(i) Metal B is the most reactive as it gives displacement reaction with iron (II) sulphate.

(ii) When metal B is added to copper (II) sulphate solution, a displacement reaction will take place because of which the blue colour of copper (II) sulphate solution will fade and a red-brown deposit of copper will be formed on metal B.

(iii)Metal B is the most reactive because it displaces iron from its salt solution. Metal A is less reactive because it displaces copper from its salt solution. Metal C is still less reactive because it can displace only silver from its salt solution and metal D is the least reactive because it cannot displace any metal from its salt solution. Hence, the decreasing order of reactivity of the metals is B > A > C > D.

4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.

Solution: Hydrogen gas is liberated when dilute HCl is added to a reactive metal.

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)

5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.

Solution: Zinc is more reactive (more electro positive) than iron. Therefore Zinc displaces Iron from its salt solution. The colour of ferrous sulphate is pale green, which turns colourless.

FeSO4 + Zn → ZnSO4 + Fe(s)

Light green     Zinc sulphate(Colourless)

Metal and Non-Metal

In-text questions set 3 Page number 49 (Metals and Non-Metals)

1. (i) Write the electron-dot structures for sodium, oxygen and magnesium.

(ii) Show the formation of Na2O and MgO by the transfer of electrons.

(iii)What are the ions present in these compounds?

Solution: (i) Sodium:

Metal and Non-Metal

Oxygen:

Metal and Non-Metal

Magnesium:

(ii) Formation of Magnesium oxide:

When magnesium reacts with oxygen, the magnesium atom transfers its two outermost electrons to an oxygen atom. By losing two electrons, the magnesium atoms form a magnesium ion (Mg2+) and by gaining two electrons, the oxygen atom forms an oxide ion (O2-). Mg:  +

Metal and Non-Metal

→ MgO

Formation of Sodium oxide:

Two sodium atoms transfer their 2 outermost electrons to an oxygen atom. By losing two electrons, the two sodium atoms form tow sodium ions (2Na+). And by gaining two electrons, the oxygen atom forms an oxide ion (O2-).

Metal and Non-Metal

(iii) The ions present in sodium oxide compound (Na2O) are sodium ions (2Na+) and oxide ions (O2-).

The ions present in Magnesium oxide compound (MgO) are magnesium ions Mg2+ and oxide ions (O2-).

2. Why do ionic compounds have high melting points?

Solution: Ionic compounds are the ones which has both positive and negative charges. Hence there will be strong force of attraction between them. This make expenditure of lot of heat to break this force of attraction hence ionic compounds have high melting points.

Metal and Non-Metal

In-text questions set 4 Page number 53 (Metals and Non-Metals)

1. Define the following terms.

(i) Mineral

(ii) Ore

(iii) Gangue

Solution:

  1. Minerals are compounds (also known as elements) which are found naturally in the earth’s crust. E.g. Alums, K2SO4.Al2(SO4)3.24H2O, etc.
  2. Ores are minerals from which metal can be extracted Ex: Bauxite Al2O3.2H2O is the ore of Al, copper pyrite CuFeS2.All minerals are not considered as ores but all ores are also minerals.
  3. Ores mined from the earth are naturally contaminated with sand, rocky materials. There are impurities present in the ore which are known as gangue.

2. Name two metals which are found in nature in the free state

Solution: Gold and platinum are the two metals found in Free State in nature.

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

Reduction method is used to obtain metal from its oxide. Ex: Zinc oxide is reduced to metallic zinc by Heating with carbon.

ZnO + C → Zn + CO

Ex: Lead oxide is reduced to lead by heating with carbon

PbO +C → Pb + CO

Metal and Non-Metal

In-text questions set 5 Page number 55 (Metals and Non-Metals)

1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

MetalZincMagnesiumCopper
Zinc Oxide
Magnesium Oxide
Copper Oxide
Metal and Non-Metal

Solution:

A more reactive metal can displace a less reactive metal from its oxide. Among Zinc, Magnesium, and Copper metals, magnesium is the most reactive, copper is the least reactive metal and zinc is less reactive .The displacement reaction will take place in the following cases

MetalZincMagnesiumCopper
Zinc OxideDisplacement
Magnesium Oxide
Copper OxideDisplacementDisplacement
Metal and Non-Metal

2. Which metals do not corrode easily?

Solution: Gold and platinum are the metals which do not corrode easily

3. What are alloys?

Solution: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Metal and Non-Metal

Exercise questions Page number 56-57 (Metals and Non-Metals)

1. Which of the following pairs will give displacement reactions?

(a) NaCl solution and copper metal

(b) MgCl2 solution and aluminium metal

(c) FeSO4 solution and silver metal

(d) AgNO3 solution and copper metal

Solution: Option d i.e AgNO3 solution and copper is correct answer. Copper displace the silver cations (reducing them to the elemental metal), in the process copper itself being oxidised to Copper II cations (Cu2+) and going into solution. So silver metal precipitating out and a copper II nitrate solution will be remaining.

Cu(s) + 2AgNO3 (aq) → Cu(NO3)2 (aq) + 2Ag (s)

2. Which of the following methods is suitable for preventing an iron frying pan from rusting?

  1. Applying grease
  2. Applying paint
  3. Applying a coating of zinc
  4. All of the above

Solution: Answer is (c) Applying a coat of Zinc

Though applying grease and applying paint prevents iron from rusting but we cannot apply these methods on frying pan hence applying a coat of Zinc is most appropriate method to prevent an iron pan from rusting.

3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

(a) Calcium

(b) Carbon

(c) Silicon

(d) Iron

Solution: Correct answer is option (a) i.e Calcium.

Calcium reacts with oxygen to give calcium oxide. Calcium oxide is soluble in water to give Calcium Hydroxide.

Carbon forms carbon-oxide with oxygen which is gas hence option B is wrong

Silicon reacts with oxygen and forms silicon dioxide. This is insoluble in water. So option C is not correct.

Iron reacts with oxygen and forms Iron dioxide. This is insoluble in water. So option D is not correct.

4. Food cans are coated with tin and not with zinc because

(a) Zinc is costlier than tin.

(b) Zinc has a higher melting point than tin.

(c) Zinc is more reactive than tin.

(d) Zinc is less reactive than tin.

Solution: Answer is c. Food cans are coated with tin and not with zinc because Zinc is more reactive that is electro positive than tin.

5. You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?

(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Solution:

  1. Metals are malleable and can be easily drown into sheets by hitting with hammer. On the other hand if we beat non-metals they break down and they cannot be drawn into sheets as they are non-malleable. Metals of good conductors of electricity hence they make bulb when you connect metals with a battery, wire and bulb. Similarly If non-metals are bad conductors of electricity chance they fail to lit up the bulb on connecting with wire and battery.
  2. These experiments can be helpful to demonstrate the malleability and electric conductivity of the metals and non-metals

6. What are amphoteric oxides? Give two examples of amphoteric oxides

Solution: Oxides that react with both acids and bases to form salt and water are known as amphoteric oxides. Examples:  PbO and Al2O3.

Amphoteric oxides are the one which reacts with both acids and bases to form salt and water. Examples:  Lead oxide – PbO and Aluminium oxide – Al2O3.

7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Solution: Zinc (Zn) and Magnesium (Mg) are the two metals which will displace Hydrogen from dilute acids as they are very reactive metals. Gold (Au) and Silver (Ag) are the metals which will not replace Hydrogen from dilute acids as these metals are less reactive.

8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Solution: In the process of electrolytic refining of metal called ‘M’, An impure and thick block of metal M. is considered as anode, Thin strip or wire of pure metal M is taken as anode A suitable salt solution of metal M is considered as the electrolyte.

9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.

(a) What will be the action of gas on

(i) dry litmus paper?

(ii) moist litmus paper?

(b) Write a balanced chemical equation for the reaction taking place.

Solution: a) When sulphur powder is burnt in the air sulphur-di-oxide is formed.

(i) Sulphur-di-oxide does not have any effect on dry litmus paper.

(ii) Sulphur-di-oxide turn the moist litmus paper from blue to red as contact of SO2 with water turns to sulfurous acid.

(b) S(s) + O2(g) → SO2(g)

SO2(g) + H2O →H2SO3

10. State two ways to prevent the rusting of iron.

Solution:

  1. Iron can be prevented from rusting by coating the surface of the iron with rust proof paints
  2. By applying Oil/grease on the surface of iron objects as it will prevent the iron surface to get in contact with air consisting of moisture.

11. What type of oxides are formed when non-metals combine with oxygen?

Solution: When non-metals combine with oxygen it forms either acidic or neutral oxides. Ex: N2O5 or N2O3 is an acidic oxide; CO is a neutral oxide.

12. Give reasons

(a) Platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium and lithium are stored under oil.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction

Solution:

(a) Platinum, gold and silver are used to make jewellery for these metals are very less reactive hence they are not affected by air, water or most chemicals. These metals have a lot of luster and they are malleable and ductile in nature and also high corrosion resistance in nature.

(b) Sodium, potassium and lithium readily react with water to produce a lot of heat. As a result, Hydrogen evolved in the reaction results in a fire. On exposure to water they react with moisture (water droplets) present in the atmosphere, In order to prevent contact with water hence these metals are stored under oil.

(c) Aluminium forms on its surface a nonreactive surface of aluminium oxide. Such coating prevents other compounds from reacting to aluminium. So aluminium is being used to produce utensils for cooking.

(d) Reducing metal oxide into free metal is easy. Additionally, because it is easier to obtain metals directly from their oxides than from their carbonates or sulphides, the carbonate and sulphide ores are first transformed to oxides to obtain the metals.

13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Solution: Tarnished copper vessels being cleaned with lemon or tamarind because this sour substance contains acids which dissolve the coating of copper oxide or basic copper carbonate present on the surface or tarnished copper vessels. This makes them shining red-brown again. Hence they are very effective in cleaning tarnished copper vessels.

14. Differentiate between metal and non-metal on the basis of their chemical properties.

Solution:

MetalsNon-metals
When metals are heated with oxygen, they form ionic oxides which are basic in nature and form bases on dissolving with water. This turn red litmus paper to blue.When non-Metals are heated with oxygen, they form covalent oxides which are acidic in nature which form acid on dissolving with water. This turn blue litmus paper to red.
They are electro positive, lose electrons readily and become a positive ion.They are electro negative, gain electrons and become negative ions.
Metals are lustrous.Non-metals are non-lustrous; graphite is the exception
Reducing agents.Good oxidizing agents.
Metals are the good conductors of electricity and heat.Non-metals are non-conductors of electricity and heat; graphite is the exception
All metals are solids except mercury.Non-metals are in solid-liquid and gaseous states
Metal and Non-Metal

15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Solution: Goldsmith used the solution called Aqua regia which is called as royal water in Latin. . It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid in the ratio of 3:1. Aqua regia is capable of dissolving noble metals like gold and platinum. When upper-layer of dull gold ornament is dissolved they lose their weight.

16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Solution: Copper is used to make hot water tanks and not steel (an alloy of iron) because copper does not reacts with either water or steam whereas iron reacts with steams to corrode the tank.

Metal and Non-Metal


NCERT Solutions for class 10 Science Chapter 3- Metals and Non-metals

Elements can be categorised into two types viz, non-metals and metals. Excluding mercury, all metals are solid at room temperature. Some other important properties of metals include

  • They are malleable
  • Lustrous
  • Good conductors of electricity and heat
  • They lose their electrons to form positively charged ions
  • They form basic oxides by combining with oxygen

What are amphoteric oxides?

Oxides which show basic and acidic properties are called amphoteric oxides. Examples are, zinc oxide and aluminium oxide.

What is metallurgy?

The process of extracting metal from ore and refining it is called metallurgy.

What is corrosion?

Corrosion is a phenomenon where a metal like iron is exposed to moistened air for a long period.

What are non-metals?

Non-metals are not ductile and malleable. Excluding graphite, all non-metals are bad conductors of electricity and heat. They gain electrons to form negative ions when they react with metals. Non-metals form hydrides by reacting with hydrogen. They can form oxides which are either neutral or acidic.

Frequently Asked Questions on Metals and Non-Metals

Why is sodium kept immersed in kerosene oil?

Sodium is a reactive metal, if kept open it will react with oxygen to explore and catch fire. Sodium metal is kept immersed in kerosene to prevent their reaction with oxygen, moisture and carbon dioxide of air.

Why do ionic compounds have high melting points ?

Ionic compounds are the ones which has both positive and negative charges. Hence there will be strong force of attraction between them. This make expenditure of lot of heat to break this force of attraction hence ionic compounds have high melting points.

Name two metals which are found in nature in the free state

Gold and platinum are the two metals found in Free State in nature.

What are alloys ?

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

What type of oxides are formed when non-metals combine with oxygen ?

When non-metals combine with oxygen it forms either acidic or neutral oxides. Ex: N2O5 or N2O3 is an acidic oxide; CO is a neutral oxide.

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron) ?

Copper is used to make hot water tanks and not steel (an alloy of iron) because copper does not reacts with either water or steam whereas iron reacts with steams to corrode the tank.

Download NCERT Notes & Solution(click here)

metal-and-non-metal

Category: Class 10th

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