RBSE Class 10 Science Important Questions Chapter 3 Metals and Non-metals

Rajasthan Board RBSE Class 10 Science Important Questions Chapter 3 Metals and Non-metals Important Questions and Answers.

RBSE Class 10 Science Chapter 3 Important Questions Metals and Non-metals

Objective Questions

Question 1.
Brass is an alloy of ………….
(a) Copper + Tin
(b) Zinc + Tin
(c) Copper + Zinc
(d) Copper + Aluminium
Answer:
(c) Copper + Zinc

Question 2.
Which method is used for metal extraction from sulphide are …………
(a) Rosting
(b) Corrosion
(c) Calcination
(d) Thermit reaction
Answer:
(a) Rosting

Question 3.
Non-metal, which is liquid at room temperature is …………
(a) Mercury
(b) Sulphur
(c) Bromine
(d) Carbon
Answer:
(c) Bromine

Question 4.
Non-metal which is lustrous is ………
(a) Caesium
(b) Sulphur
(c) Iodine
(d) Phosphorous
Answer:
(c) Iodine

Question 5.
Which of the following non-metal is good conductor of electricity?
(a) Iodine
(b) Graphite (carbon)
(c) Diamond (carbon)
(d) Sulphur
Answer:
(b) Graphite (carbon)

Question 6.
In which of the following solvent, ionic compounds are soluble?
(a) Benzene
(b) Petrol
(c) Water
(d) Kerosene
Answer:
(c) Water

Question 7.
The Alloy used for the welding of electrical wires is …………
(a) Bronz
(b) Brass
(c) Solder
(d) Bell metal
Answer:
(c) Solder

Very Short Answer Type Questions

Question 1.
Write some physical properties of metals.
Answer:
Metals are generally heavy, lustrous, ductile and malleable. These are good conductor of heat and electricity.

Question 2.
Write the name and formula of one ore of Aluminium.
Answer:
Ore of Aluminium – Bauxite.
Formula – Al₂O₃.2H₂O.

Question 3.
Write name of three metals by which coins are prepared.
Answer:
(i) Copper (Cu)
(ii) Silver (Ag)
(iii) Gold (Au).

Question 4.
What is ‘Metallic lustre’ ?
Answer:
Metals, in their pure state, have a shining surface. This property is called metallic lustre.

Question 5.
What is Roasting?
Answer:
The sulphide ores are converted into oxides by heating strongly in the presence of excess air, this process is called roasting.

Question 6.
What are sonorous metals ?
Answer:
The metals that produce a sound on striking a hard surface are said to be sonorous.

Question 7.
Why electric wires have a coating of PVC or a rubber like material ?
Answer:
Electric wires are made up of electrical conductor metals whereas materials like PVC and rubber are bad or poor conductors due to which the electric shock caused by touching electric wire can be avoided.

Question 8.
Why school bells are made of metals?
Answer:
Metals produce a sound on striking a hard surface therefore, School bells are made of metals so that the sound can be heard far away.

Question 9.
Name two metals that do not react with oxygen even at very high temperature.
Answer:
‘Silver’ and ‘Gold’ do not react with oxygen even at very high temperature.

Question 10.
Why the rusting of iron occurs?
Answer:
When iron is exposed to moist air for a long time it acquires a coating of a brown substance, called rust. Rust is a mixture of Iron oxide (Fe₂O₃) and Iron hydroxide [Fe(OH)₃],

Question 11.
Pure gold have how many carat?
Answer:
24 carat.

Question 12.
Name the metals that react neither with cold water nor with hot water but react with steam to give oxide and carbon.
Answer:
Aluminium, Iron and Zinc.

Question 13.
Which components are present in the alloy, known as solder?
Answer:
Alloy, solder have two component—lead and tin.

Question 14.
Why ores of many metals are oxide?
Answer:
Ores of many metals are oxide because oxygen is very reactive element and is very abundant on the earth.

Question 15.
Write the formulae of following ores – (i) Haematite (ii) Copper pyrites.
Answer:

1. Haematite (Fe₂O₃)
2. Copper pyrites (CuFeS₂).

Question 16.
Which method is used for the extraction of more reactive metals?
Answer:
Extraction of more reactive metals is performed by the electrolysis of their salts.

Question 17.
Write the name of Electrolyte used in the purification of copper.
Answer:
Copper sulphate (CuSO₄) solution.

Question 18.
Malleability of which metal is maximum?
Answer:
Gold and Silver are most malleable metals.

Question 19.
Name the metals which melts when kept on palm?
Answer:
Galium and Caesium, because the melting point of these metals is very low.

Question 20.
Name one ore of mercury.
Answer:
Cinnabar (HbS).

Question 21.
What is allotrope?
Answer:
Different forms of an element which have different properties are called allotropes. Diamond and Graphite are allotropes of Carbon.

Question 22.
Which natural substance is hardest?
Answer:
Diamond is a hardest natural substance.

Question 23.
What is formed when metals reacts with dilute acids?
Answer:
Salt and Hydrogen are foremd by the reaction of metals with dilute acids.
Metal + Dilute acid →Salt + H₂
Example – Mg, Al, Zn, Fe

Question 24.
What is the composition, of Aquaregia?
Answer:
Aquaregia is a mixture of concentrated HNO₃ and concentrate HCl in 1 : 3 ratio.

Question 25.
What is Calcination ?
Answer:
The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.

Question 26.
Ionic compounds do not conduct electricity in solid state, why?
Answer:
In the solid state the movement of ions is not possible due to their rigid struc¬ture so ionic compounds do not conduct electricity.

Question 27.
Classify the metals on the basis of their reactivity.
Answer:
Metals are classified in three categories on the basis of their reactivity,
(i) least reactive metals
(ii) medium reactive metals
(iii) highly reactive metals.

Question 28.
What is rust?
Answer:
When iron is exposed to moist air for long time, it acquires a coating of brown substance, called rust.

Question 29.
What is Galvanisation?
Answer:
Galvanisation is a method of protecting iron and steel from rusting by coating them with a thin layer of zinc.

Question 30.
Write the balanced chemical equation of thermit reaction.
Answer:
Fe₂O_3(s) + 2Al_(s) → 2Fe_(l) + Al₂O_3(s) + Heat

Question 31.
What is Amalgam?
Answer:
When alloy is prepared, if one of the metals is mercury, then the alloy formed is called amalgam.

Question 32.
The reactivity of noble gases is very low, why?
Answer:
The reactivity of noble gases is very low due to complete valance shell.

Question 33.
What is reactivity series ? Write its one use.
Answer:
The reactivity series is a list of metals arranged in the order of their decreasing activities.
Use : Reactivity series help in extraction of metal from any ore.

Question 34.
Which metals can be obtained in their pure form by electrolytic refining ?
Answer:
Copper, Zinc, Tin, Nickel, Silver, Gold, etc.

Question 35.
What is ‘anode mud’ ?
Answer:
When pure metal is obtain through electrolytic refining, then the insoluble impurities settle down at the bottom of the anode and are known as anode mud.

Question 36.
Name the components of ‘bronze’ alloy. Describe one feature of this alloy.
Answer:
‘Bronze’ is an alloy of copper (Cu) and tin (Sn). Bronze is not good conductor of electricity.

Question 37.
Why metals are used in making cooking utensils ?
Answer:
Metals are conductor of heat and their melting point is very high, therefore, they are used in making utensils.

Short Answer Type Questions

Question 1.
Give the general properties of metals.
Answer:
General properties of metals are as follows –

1. In the pure state metals have shining surface, this property is called metallic lustre.
2. Metals are generally solid and hard and the hardness of different metals is different.
3. Metals are malleable and ductile.
4. Metals are good conductor of heat and have high melting point so these are used for making cooking vessels.
5. Metals are good conductors of electricity. So electric wires are coated with a layer of Polyvinyl chloride or Rubber. This layer is bad conductor of electricity.
6. Metals are sonorous means they produce a sound on striking a hard surface.

Question 2.
Write the general properties of non-metals.
Answer:
General properties of non-metals are as follows –

1. Non-metals may be solid, liquid (Bromine) or gas at ordinary temperature.
2. Non-metals are not lustrous but iodine is lustrous, although it is non-metal.
3. The melting point and boiling point of non-metals is less than metals.
4. Non-metals are not malleable and ductile. .
5. Non-metals are bad conductor of electricity, exception – Graphite
6. Non-metals are not sonorous.

Question 3.
What happens when magnesium and sulphur are burned prepare the solution of compound formed in water and test the solution with litmus and decide that which element forms acidic oxide and which forms basic explain with equations.
Answer:
(1) When magnesium is burned in air, magnesium oxide is formed with white shiny flame, which is basic because Mg is metal and metal oxides are generally basic. Magnesium hydroxide is formed when this oxide is dissolved in water, which turns red litmus into blue.
2Mg_(s) + O₂ → 2MgO_(s)
MgO_3(s) + H₂O(l) → Mg(OH)_2(aq)
(2) Sulphur dioxide is formed when sulphur is burned in air, which is acidic because sulphur is non-metal and non-metal oxides are generally acidic. Acidic solution (H₂SO₃) is formed when this oxide is dissolved in water which turns blue Litmus into red.
S_(s) + O_2(g)→ SO_2(g)

Question 4.
What happens when copper (Cu) and aluminium (Al) are heated in presence of air? What is the nature of oxides formed. Explain with reactions are metal oxides soluble in water?
Answer:
When copper is heated in presence of air, it reacts with oxygen and forms black coloured copper (II) oxide.

Similarily, Aluminium forms Aluminium oxide

Metal oxides are generally basic in nature. But some metal oxides, such as aluminium oxide, zinc oxide etc./show both acidic as well as basic behaviour. Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. Aluminium oxide reacts ,in the following manner with acids and bases –

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows –
Na₂O_(s) + H₂O(l) → 2NaOH_(aq)
K₂O_(s) + H₂O(l) → 2KOH_(aq)

Question 5.
Explain the reactivity of Mg, Al, Zn, Pb, K, Na, Fe, Cu, Ag etc. metals by the comparison of reaction with oxygen.
Answer:
All metals do not react with oxygen at the same rate. Different metals show different reactivities towards oxygen. Potassium (K) and sodium (Na) react vigorously with oxygen and catches fire if kept open. At ordinary temperature, the surfaces of metals such as magnesium (Mg), aluminium (Al), zinc (Zn), lead (Pb) etc. are covered with a thin layer of oxide. This layer of oxide prevents the metal from further oxidation. Iron (Fe) does not bum on heating but iron filings bum vigorously when sprinkled in the flame of the burner.
Copper (Cu) does not bum but the hot metal is coated with a black coloured layer of copper (II) oxide. Silver and gold do not react with oxygen even at high temperature. So the reactivity order of metals mentioned above are as follows :
K > Na > Mg > Al > Zn > Fe > Pb > Cu > Ag

Question 6.
Reaction of metals with water depends on the reactivity of metal. Explain with example of different metals.
Answer:
Metals react with water and produce a metal oxide and hydrogen (H₂) gas. Some metal oxides that are soluble in water dissolve in water and forms metal hydroxide. But all metals do not react with water.
Metals like potassium (K) and sodium (Na) react violently with cold water. This reaction is so violent and exothermic that the evolved hydrogen gas (H₂) immediately catches fire.
2K_(s) + 2H₂O(l) → 2KOH_(aq) + H_2(g) + Heat energy
2Na_(s) + 2H₂O(l) → 2NaOH_(aq) + H_2(g) + Heat energy
The reaction of calcium with water is slow or less violent and the heat evolved here is not sufficient for the hydrogen to catch fire.
Ca_(s) + 2H₂O(l)→ Ca(OH)_2(aq) + H_2(g)
Magnesium does not react with cold water. But it reacts with hot water to form magnesium hydroxide and hydrogen gas.
Metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.
2Al_(s) + 3H₂O(g) → Al₂O_3(s) + 3H_2(g)
3Fe_(s)+ 4H₂O(g) → Fe₃O_4(s)+ 4H_2(g)
Metals such as lead, copper, silver and gold do not react with water at all.

Question 7.
What is Anodising? Write the use of it.
Answer:
Anodising – Anodising is a process of forming a thick oxide layer of aluminium. Aluminium develops a thin oxide layer when exposed to air. Ibis aluminium oxide layer makes it resistant to corrosion. The resistance can be imporved further by making the oxide layer thicker. For anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid (H₂SO₄). The oxygen gas evolved at the anode reacts with aluminium to make a thicker oxide layer. This oxide layer can be dyed easily to form attractive aluminium articles.

Question 8.
Why calcium and magnesium floats when they react with water ?
Answer:
Metals react with water and produce a metal oxide and hydrogen gas. The reaction of calcium with water is slow.
Ca_(s) + 2H₂O_(l)Ca(OH)_2(aq) + H_2(g) + Heat energy
The heat evolved is not sufficient for the hydrogen to catch fire and therefore the bubbles of hydrogen gas formed stick to the surface of calcium metal and as a result calcium starts floating. Similarly, magnesium reacts -with hot water to form magnesium hydroxide and hydrogen. It also starts floating because bubbles of hydrogen gas sticking to its surface.

Question 9.
Explain the reaction of metals with Acids.
Answer:
Generally metals react with acids to give corresponding salt and Hydrogen gas.
Metal + Dilute Acid → Salt + Hydrogen
Mg_(s) + 2HCl_(aq) → MgCl_(aq) + H_2(g)
Zn(s) + H2SO₄(aq) → ZnSO₄(aq) + H_2(g)
Reactivity order of Mg, Al, Zn, Fe and Cu with dilute hydrochloric acid is as follows –
Mg > Al > Zn > Fe > Cu
The reaction with magnesium is most exothermic. Copper does not react with dilute HCl.
Hydrogen gas is not evolved when metals reacts with nitric acid. But magnesium (Mg) and manganese (Mn) react with very dilute HNO₃ to evolve H₂ gas.

Question 10.
What is reactivity series? On the basis of this explain that, reaction of metal with solutions of other metal salts is possible or not.
Answer:
Reactivity series: The reactivity series is a list of metals arranged in the order of their decreasing activities. The reactivity or activity series is as follows –

More reactive metals can displace les reactive metals from solution of their salt (compound) or molten form. If metal A displaces metal B from its solution. It is more reactive than B.
Metal A + Salt solution of B → Salt solution of A + Metal B
Example –
\(\mathrm{Cu}^{+2} \mathrm{SO}_{4}^{-2}\) _(aq) + Fe_(s) → FeSO_4(aq) + Cu_(s)
This reaction proves that Fe is more reactive than Cu. The reaction opposite to this is not possible.

Question 11.
Hydrogen gas is evolved when metals reacts with acid, but hydrogen gas in not evolved when metal reacts with nitric acid. Why ?
Answer:
Hydrogen gas is not evolved when metal reacts with nitric acid because HNO₃ is a strong oxidising agent. It oxidises the H₂ produced to water and itself get reduced to any of the nitrogen oxides (N₂O, NO, NO₂). Like –
Zn + 4HNO₃ → Zn(NO₃)₂ + 2NO₂ + 2H₂O

Question 12.
What happens when (a) A strip of copper is added in the solution of silver nitrate?
(b) A strip of Zn is added in the solution of copper sulphate?
Answer:
(a) When a strip of copper is dipped in the solution of silver nitrate, then Ag separate out from the solution and copper nitrate is formed due to which solution becomes blue, because copper is more reactive than silver
2AgNO_3(aq) + Cu_(s) → Cu(NO₃)_2(aq) + 2Ag_(s)

(b) When a strip of zinc is dipped in the solution of copper sulphate then copper separate out from the solution. The blue colour of copper sulphate solution dis¬appears and zinc sulphate is formed because zinc is more reactive than copper.
CuSO_4(aq) + Zn_(s) → ZnSO_4(aq) + Cu_(s) Blue Colourless

Question 13.
In which state metals exist in the nature? Explain.
Answer:
The earth’s crust is the major source of metals. Seawater also contains some soluble salts such as sodium chloride (NaCl), magnesium chloride (MgCl₂) etc.
Some metals are found in the earth’s crust in the free state. Some are found in the form of their compounds. The metals at the bottom of the reactivity series are the least reactive. They are often found in a free state. For example, gold, silver, platinum and copper are found in the free state. Copper and silver are laso found in the combined state as their sulphide or oxide ores.

The metals at the top of the activity series (K, Na, Ca, Mg and Al) are so reactive that they are never found in nature as free state. The metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s crust mainly as oxides, sulphides or carbonates. The ores of many metals are oxides. This is because oxygen is a very reactive element and is very abundant on the earth.

Question 14.
Write difference between roasting and calcination.
Answer:

Roasting	Calcination
1. This process is used for sulphide ore.	This process is used for carbonate ore.
2. In this ores are converted	In this ores are converted into oxides by heating strongly in limited air.
3. Example- 2ZNSS + 3O2(g) 2ZnO(S) + 2SO(g)	Example – ZnCO3(S)  ZnO(S) + CO(g)

Question 15.
Prepare a chart of steps involved in the extraction of pure metal from ore.
Answer:
The steps involved in the extraction of pure metal from ore can be represented by the following chart –

Question 16.
In which unit the purity of gold is measured? Pure gold is not suitable for making ornaments, why?
Answer:
The purity of gold is measured in carat. Pure gold, known as 24 carat gold, is very soft. It is, therefore, not suitable for making ornaments. It is alloyed with silver or copper to make it hard. Generally, in India 22 carat gold is used for making ornaments. It means that 22 parts of pure gold is alloyed with 2 parts of copper or silver.

Question 17.
(a) Silver articles become black after some time when exposed to air, why?
(b) Why does the shiny brown colour of copper disappears is humid air.
Answer:
(a) Silver articles become black after sometime when exposed to air, because it reacts with sulphur present in the air to form coating of silver sulphide.
(b) Copper reacts with moist carbon dioxide in the air and gains a green coat of basic copper carbonate, as a result copper slowly loses its shiny brown surface.

Question 18.
Zinc is more electropositive than iron, so corrosion of it should be faster than iron but it does not happens while it is used in the Galvanisation of Iron for portection, why?
Answer:
A basic layer of zinc carbonate [ZnCO₃] is formed on it when zinc comes in contact of moist air. This layer protects the zinc for further reaction. So corrosion of zinc not occurs that is why it is used in the protection of iron from rusting.

Question 19.
What is thermit reaction. Give the balance chemical equation for the reaction.
Answer:
The highly reactive metals such as sodium, calcium, aluminimum, etc. are used as reducing agents because they can displace metals of lower reactivity from their compounds. These displacement reactions are highly exothermic. The amount of heat evolved is so large that the metals are produced in the molten state.
The reaction of iron (III) oxide (Fe₂O₃) with aluminium is used to join railway tracks or cracked machine parts. This reaction is known as the thermit reaction.
Fe₂O_3(s) + 2Al_(s) → 2Fe_(l) + Al₂O₃ + Heat

Question 20.
(a) Iron is never used in its pure state, why?
(b) Which process is used to increase the hardness of Iron? How the stainless steel (steel), is prepared from this?
Answer:
(a) Iron is never used in the pure state because pure iron is very soft and streches out on heating.
(b) To increase the hardness of iron it is mixed with a small amount of carbon (about 0. 05%) due to which iron becomes hard and strong. To obtain stainless steel iron is mixed with nickel and chromium, which is hard and does not rust. Thus, if iron is mixed with some other substances its properties change.

Question 21.
What change is observed in electrical conductivity and melting point of an alloy than that of pure metals ? Explain with example.
Answer:
The electrical conductivity and melting point of an alloy is less than that of pure metals. For example, brass, an alloy of copper and zinc (Cu and Zn), and bronze, an alloy of copper and tin (Cu and Sn), are not good conductors of electricity whereas copper is used for making electrical circuits. Solder, an alloy of lead and tin (Pb and Sn), has a low melting point and is used for welding electrical wires together.

Question 22.
How the extraction of metals, present in the lower side of activity series, is performed? Explain.
Answer:
Metals present in the lower side of the activity series are very less reactive. The oxides of these metals gives to metals by heating only. For example, cinnabar (HgS) is an ore of mercury. When it is heated in air, it is first converted into mercuric oxide (HgO). Mercuric oxide is then reduced to mercury on further heating.

Similarly, copper which is found as Cu₂S in nature can be separated from its ore by just heating in air.

Question 23.
Which method is used for the extraction of metals, present on the upper side of activity series? Explain with examples.
Answer:
The metals (K, Na, Ca, Mg and Al) present on the upper side of activity series are very reactive. They can not be obtained from their compounds by heating with carbon. For example, carbon cannot reduce the oxides of sodium, magnesium, calcium, aluminium, etc., to the respective metals, because these metals have more affinity for oxygen than carbon. So these metals are obtained by electrolytic reduction. For example, sodium, magnesium and calcium are obtained by the electrolysis of their molten chlorides. The metals are deposited at the cathode (the negatively charged electrode) and chlorine is liberated at the anode (the positively charged electrode). The reactions are as follows –
At Cathode Na⁺+ e^– →Na
A Anode 2Cl^–→ Cl₂ + 2e ^–

Similarly, aluminium is obtained by the electrolytic reduction of aluminium oxide.
Mg is obtained by the electrolysis of molten MgCl_2.

Reduction occurs at cathode and oxidation at anode.

Question 24.
Why the concentration of ores is performed?
Answer:
Ore have different impurities like sand, soil, gravels etc. which are called gangue. These impurities are removed by the process of concentration. After the process of concentration ores becomes more suitable for the extraction of metal.

Question 25.
Differentiate between enrichment of ores and refining of metals.
Answer:

Enrichment of ores	Refining of metals
1. Enrichment of ores is the processes used for removing the gangue	The metals pro-duced by various reduction process contain impurities which must be removed to obtain pure metals and the process used is refining of metals.
2. In this process different reduction processes are used.	For this process electrolytic refining is used.

Question 26.
A metal is treated with Dilute H₂SO₄. The gas evolved is collected by the method shown in the figure. Answer the following –
(a) Give the name of gas.

(b) Give the name of method by which gas is collected.
(c) Gas is soluble in water or not.
(d) Gas is lighter than air or heavier.
(e) Write the chemical formula of gas.
Answer:
(a) Hydrogen gas.
(b) The gas is collected by Distillation method.
(c) Gas is not soluble in water.
(d) Gas is lighter than air.
(e) Chemical formula of gas is H₂

Question 27.
Ionic compounds do not conduct electricity in the solid state but in molten state or in aqueous solution conducts electricity. What is the scientific reason behind it.
Answer:
Ionic compounds do not conduct electricity in the solid state because movement of ions is not possible in the solid due to their rigid structure. But ionic compounds conduct electricity in the molten state or in aqueous solution because in these states electrostatic forces of attraction between the oppositely charged ions become weak so the ions move freely and conduct electricity.

Essay Type Questions

Question 1.
Explain the formation of ionic compound by the reaction of metals and non-metals and give the general properties of ionic compounds also.
Answer:
Metals are electropositive so forms cations by the loss of electrons easily and non-metals are electronegative so gains electrons from metal and forms anion, the attraction between these ions is called ionic bond. The compounds having ionic bond are called ionic compounds.
Example – Formation of NaCl

Sodium atom has one electron in its outermost shell. If it loses the electron from its M shell then its L shell now becomes the outermost shell and that has a stable octet. The nucleus of this atom still has 11 protons but the number of electrons has become 10, so there is a net positive charge forms sodium cation (>Na⁺). But chlorine has seven electrons in its outermost shell and it requires one more electron to complete its octet.

When sodium and chlorine reacts the electron lost by sodium could be taken up by chlorine. After gaining one electron, the chlorine atom gets a unit negative charge, because its nucleus has 17 protons and there are 18 electrons in its all (K, L and M) shells. This gives us a chloride anion Cl . So both these elements can have a give and take relation between them as follows :

Sodium and chloride ions, being oppositely charged, attract each other and are held by strong electrostatic forces of attraction to exist as sodium chloride (NaCl). Here sodium chloride does not exist as molecules but aggregates of oppositely charged ions.
Formation of MgCl^2– Mg forms Mg²⁺ by giving two electrons and these two electrons are gained by two chlorine atom so two Cl are formed.

The compounds formed by the transfer of electrons from a metal to a non-metal are called ionic compounds or electrovalent compounds.
General Properties – The general properties of ionic compounds are as follows –
(i) Physical nature – Ionic compounds are solids and hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.

(ii) Melting and Boiling points – Ionic compounds have high melting and boiling points because a considerable amount of energy is required to break the strong interionic attraction.

(iii) Solubility – Electrovalent compounds are generally soluble in water and insoluble in solvents such as kerosene, petrol etc.

(iv) Conduction of Electricity:
The conduction of electricity through a solution involves the movement of charged particles. A solution of an ionic compound in water have ions, which move to the opposite charge electrodes when electricity is passed through the solution. Ionic compounds do not conduct electricity in the solid state because movement of ions in the solid is not possible due to their rigid structure. Bot ionic compounds conduct electricity in the molten state because in the molten state electrostatic forces of attraction between the oppositely charged ions becomes weak due to the heat. Thus, the ions move freely and conduct electricity.

Question 2.
Prove with an activity that metals are good conductors of heat.
Answer:
Metals are good conductors of heat, to prove this the following activity is performed –

1. Take an aluminium or copper wire. Clamp this wire on a stand.
2. Fix a pin to the free end of the wire using wax.
3. Heat the wire with a spirit lamp, candle or a burner near the place where it is clamped.
4. After some time, we observe that the pin falls down due to melting of wax but the wire does not melt.
The above activity shows that metals are good conductors of heat and have high melting point.

Question 3.
Explain the extraction of metals present in the middle of the activity series in detail.
Answer:
The metals in the middle of the activity series such as iron, zinc, lead, copper, etc., are moderately reactive. These metals are usually present as sulphides or carbonates in nature. It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates, so prior to reduction, the metal sulphides and carbonates are convereted into metal oxides.

The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting, the carbonate ores are changed into oxides by heating strongly in limited air. This process is called calcination. The chemical reaction that takes place during roasting and calcination of zinc ores are as follows –

Obtaining metals from their compounds is a reduction process. Beside this, displacement reactions is also used. The highly reactive metals such as sodium, calcium, aluminium, etc. are used as reducing agents because they displace metals of lower reactivity from their compounds. For example, when manganese dioxide is heated with aluminium powder, the following reaction takes place –
3MnO_2(s) + 4Al_(s) → 3Mn(l) + 2Al₂O_3(s) + Heat
In this reaction MnO₂ is reduced and Al is oxidised.
These displacement reactions are highly exothermic and the amount of heat evolved is so large that the metals are produced in the molten state.

Question 4.
How will you differentiate bet-ween metals and non-metals?
Answer:
Difference in the properties of metals and non-metals –

Metals	Non-metals
1. These are solid at ordinary temperature (exception — mercury)	1. These exist in all the three states at ordi-nary temperature, sulphur and phosphorous exists as solid, H2O2 and N2 as gas and Bromine as liquid.
2. These are ductile and malleable.	2. These are brittle.
3. These have metallic lustre.	3. These are not lustrous but diamond, graphite and iodine are exception.
4. These are good conductor of heat and electricity. Exception — Bismuth	4. Except graphite, all the non-metals are bad conductor of electricity.
5. Melting point and boiling point of these are High.	5. Melting point and boiling point of these are low. Exception— graphite and diamond.
6. The hardness of every metal is different from other metal. Metals like Fe, Cu and A1 are very hard, opposite to this metals like Na, K and Li are so soft that they can cut with knife also.	6. Mainly soild non metals are soft only one non metal dia-mond (Allotrope of carbon) is very hard.
7. These are not transparent.	7. Gasesous non metals are transparent.

Difference in Chemical Properties

Metals	Non-metals
1. Metals forms basic oxides.	1. Non-metals forms acidic and Neutral oxides.
2. Metals reacts with acids to give a salt and hydrogen gas.	2. These does not gives Hydrogen gas by the reaction with acids.
3. These are electropositive.	3. These are electro negative.
4. These forms chlorides by the combination with chlorine, which are electrovalent. .	4. These also forms chlorides by the combination with chlorine but these chlorides are covalent.
5. Metals are reducing agents.	5. Non- metals are oxidising agents.
6. Metals forms cations in aqueous solution	6. Non-metals forms anions in aqueous solution.

Question 5
Explain the action of steam on a metal with the help of a labelled diagram.
Answer:
Metals react with water and produce a metal oxide and hydrogen gas. But metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.
2Al_(s) + 3H₂O_(g) → Al₂O_3(s) + 3H_2(g)3Fe_(s) + 4H₂O_(g) → Fe₃O_4(s) + 4H_2(g)

Question 6.
What is Alloys? Descirbe the aims of formation of these.
Answer:
Alloy – An alloy is a homogeneous mixture of two or more metals, or a metal and a non metal. It is prepared by first melting the primary (main) metal, and then dissolving the other elements in it in definite proportions. It is then cooled to room temperature. The electrical conductivity and melting point of an alloy is less than pure metals.
Stainless steel, Brass, Bronze and Solder etc. are alloys.

Aim of formation of Alloy –

1. To increase hardness – Stainless steel is prepared by mixing small amount of carbon, nickel and chromium in the iron, which is harder than iron. Hardness increases as when copper is mixed in gold and lead in silver.
2. To increase the strongness alloys like steel – Duralium (Alloy of aluminium) are strong due to hardness.
3. To prevent corrosion – The alloys like stainless steel, alloy of zinc and iron does not corrode.
4. To decrease the melting point –
   Solder, an alloy of lead and tin (Pb and Sn), has a low melting point so it is used for welding electrical wires together.
5. Domestic Use – Alloys are used in all places like houses, industries and offices. Example – alloys are used in the formation of domestic utensils, Almirah, Fans, Refrigerators, Machines, Gear of Vehicles, Vehicles of transport and statues.

Question 7.
What is rust? Describe the conditions which are required for rusting. Write the important methods to prevent rusting of iron.
Answer:
Rust – When iron is exposed to moist air for a long time it acquires a coating of a brown substance, called rust. This is a mixture of iron (III) oxide and iron (III) hydroxide.

The surface of iron becomes weak due to rusting due to which the articles made of iron are damaged.
Air and moisture are required for rusting of iron, which can be explained by the following activity.

Activity –
(1) Three test tubes (A, B and C) are taken and clean iron nails are placed in each of them.

(2) Some water is poured in test tube A and cork it. In test tube B boiled distilled water, and 1 ml oil are poured and cork it. The oil floats on water and prevent the air to dissolve in the water.

(3) Some anhydrous calcium chloride is taken in test tube C and cork it. Anhydrous calcium chloride will absorb the moisture, from the air. Leave these test tubes for a few days and then observe.

Observations and Result –
It is observed that iron nails rust in test tube A, but they do not rust in test tubes B and C, because in the test tube A, the nails are exposed to both air and water. In the test tube B, the nails are exposed to only water, and the nails in test tube C are exposed to dry air. So it is concluded that for the rusting of iron air and moisture both are required.
Measures for the Prevention of rusting of iron – Rusting of iron can the prevented by the use of following measures –

1. By forming layer of oil or grease on the surface of iron.
2. By painting the surface of iron.
3. By forming layer of plastic on the surface of iron.
4. By galvanising the iron (forming thin layer of zinc on iron articles).
5. By chrome plating on iron.
6. By anodising.
7. By making alloys.

Question 8.
What is ore? Describe the electrolytic refining for the purification of copper, with diagram.
Answer:
Ore – The mineral from which extraction of metal is covenient and economically profitalbe is called ores.
Electrolytic refining for the purification of copper – Many metals, such as copper, zinc, tin, nickel, silver, gold, etc., are refined by electrolysis. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. The apparatus is set up as shown in figure given below. On passing the current through the electrolyte, the impure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode, and soluble impurities go into the solution, whereas, the insoluble impurities deposited at the bottom of the anode, which is called anode mud.

Question 9.
Explain with example how metals react with solutions of other metal salts ?
Answer:
Reaction of metals with solutions of other metal salts can be understood with the following activity –
(i) ‘Fake two test tubes and add solution of copper sulphate in one test tube and add solution of iron sulphate in other test tube.
(ii) Take a clean wire of copper and an iron
(iii) Put the copper wire in iron sulphate solution and put the iron nail in the solution of copper sulphate.

(iv) After 20 minutes it is observed that the blue solution of copper sulphate turns into a light green solution while there is no change in the solution of iron sulphate.
(v) ‘Ibis reaction can be represented by the following equation –

In this activity, iron displaces less reactive metal copper from its compound solution.
Thus – it can be concluded that the more reactive metal displaces the less reactive metal from its salt solution