CBSE Class 8 Science Metal And Non Metals Notes

METALS & NON-METALS

INTRODUCTION
There are 118 chemical elements known at present on the basis of their properties all these elements can be broadly divided into two main groups metals and non-metals.
A majority of the known elements are metals. All metals are solid except mercury, which is a liquid metal. There are 22 non metals, out of which 10 nonmetals are solids, one nonmetal (bromine) is a liquid and remaining 11 nonmetals are gases.

METALS
The elements which are hard, lustrous and polished, drawn into thin wires (ductile), hammered into sheets (malleable) and good conductor of heat and electricity are called metals. Such as gold, silver, copper, aluminium (Al is the most abundant metal) and zinc.
Exceptions :- Sodium and potassium are soft metals which can be cut with a knife.

NON-METALS
The elements which are usually brittle and can not be used to make sheets or wires, can not be polished and bad conductor of heat and electricity (except graphite) are called non-metals. Such as sulphur, phosphorus, oxygen, nitrogen etc. Oxygen is the most abundant element on the earth.

OCCURRENCE
Generally, metals and non-metals occurs in nature in free as well as in combined state. The metals which can not be affected by air and water are occur in native or free state and such metals are known as native metals. For example, gold and platinum. The reactive metals such as sodium, potassium, calcium, aluminium, copper etc. are found in nature in combined state in the form of compounds. The silver and copper metals occur in nature, in free as well as in the combined state. The non-metals, which are usually reactive are found in the form of compounds, and other which are less reactive, found in free state. For example, oxygen and nitrogen (Air). Thus most of the metals and non-metals are formed in nature in the form of compounds. These are
as follows :

OCCURRENCE OF METALS

POSITION OF METALS AND NON-METALS IN THE PERIODIC TABLE

The elements which are placed on the left hand side and in the centre of the periodic table are called metals. Such as sodium potassium, magnesium and calcium. Exception hydrogen, it shows the some characteristic properties of metals and some of non-metals. So, it is also called notorious element. The elements which are placed on the right hand side of the periodic table are called Non-metals. Such as oxygen, nitrogen, chlorine, fluorine etc.
In the periodic table metals and non-metals are separated from each other by a zig-zag line. The elements which are placed in the zig-zag line show some properties of metals and some properties of non-metals are called metalloids. Such as boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and Astatine (At).

The position of metals, non-metals and metalloids are shown in a simple form in fig. of periodic table –
The metals which are present at the extreme left are known as light metals while those present in the centre of the periodic table are called heavy metal or transition metals. In general, the metallic character of element decreases on going from left to right side in the periodic table.
For Example :
Sodium is more metallic than aluminium because sodium is on the left hand side of aluminium. However, on going down the group the metallic character increases.
For Example :
Carbon is non-metal while lead is metal due to their position, carbon placed at the top and lead placed at the bottom in the 14th group of the periodic table.

DO YOU KNOW
1. What are metals ?
2. What are non-metals ?
3. What are native metals ?
4. Which non-metal is most abundant element on the earth ?
5. Which metals & non-metals are found in free state in nature ?
6. Which element (metals & non metals) are found in combined state in nature ?
7. Why copper and silver metals occur in nature, in free as well as in the combined state while sodium
potassium , calcium etc. are found in combined state ?

ELECTRONIC NATURE OF METALS AND NON-METALS
According to electronic view "An element is called metal which form positive ions by losing electrons. For example, sodium is a metal which form sodium ion (Na+) by losing one electron.

Similarly, Magnesium metal (Mg) forms Mg2+ ion by losing two electrons and Al metal form Al3+ ion by losing three electrons. Thus, metals are also known as electropositive elements.
The atoms of metals have 1 to 3 electrons in their outermost shell or valence shell. For example all the alkali metals have one electron in their outermost shell. (Lithium – 2,1; Sodium – 2, 8, 1; Potassium – 2, 8, 8, 1, ....etc) Since, sodium, magnesium and aluminium are metals whose atomic number are 11, 12 & 13 respectively.
So, the electronic configuration of these are –

The outermost shells of these elements contain 1, 2 and 3 electrons. It's clear that metals have only 1 to 3 electrons in the valence shell or outermost shell of their atoms. The no. of outermost electrons which lost easily by an atom is called its valency.
An element is called non-metal which form negative ions by gaining of electrons. For example, oxygen is a non-metal which form O–2: ions by gaining two electrons.
Similarly, Chlorine, Fluorine and Iodine form Cl–, F– and I– ion by gaining one electron Thus, non-metals are also known as electronegative elements.
The atoms of non-metals have usually 4 to 8 electrons in their outermost shell.

For Example :
The atomic number of carbon, nitrogen, oxygen, fluorine and neon are 6, 7, 8, 9 and 10 respectively.
The electronic configuration of these non-metals are as follow –

Their outermost shell contain 4, 5, 6, 7 and 8 electron. Non-Metals have two exceptions : hydrogen and helium
Hydrogen is a non-metal, have 1 electron in its outermost shell or valence shell of its atom and Helium have 2 electrons in its valence shell of its atom.

Q. According to electronic concept what are metals & non-metals ?
Q. What is valency ?
Q. Name the element which is notorious.
Q. Where are the metals and non metals placed in the periodic table ?
Q. What are metalloids ?
Q. Name the three elements which are metalloids.

PHYSICAL PROPERTIES OF METALS AND NON-METALS
The important physical properties of metals and non-metals are given below :

1. Physical State :

Most of the metals are solid under normal condition of temperature and pressure. For example, iron, copper, magnesium and aluminium.

Exception : Mercury (Hg) which exist in liquid state at room temperature. Non-Metals can exist in all the three physical state i.e., solid, liquid and gases.

For Example :
Carbon, sulphur, phosphorus and iodine are solid non-metals. Bromine is liquid and oxygen, nitrogen, chlorine, fluorine are gaseous non-metals

2. Hardness :
Most of the metals are hard except sodium and potassium which are soft metals and can be easily cut with a knife. The hardness of metals varies from metal to metal. For example, Iron, Aluminium, Magnesium, Copper etc.
Non-metals are soft. Except :- diamond, it is an allotrope of carbon.

3. Malleability :
The property of metal in which they can be beaten with a hammer to form thin sheets without breaking is called malleability.
Metals are generally malleable except sodium, potassium and calcium. Gold and silver are the most malleable metals, Aluminium and copper are also highly malleable metals. All of these metals can be beaten with a hammer to form very thin sheets are called foils.
Non-metals do not show this property due to brittleness, they are broken into small pieces. For example, sulphur, coal and phosphorus are brittle non-metals.

4. Ductility :
Ductility is also an important property of metals. The ability of metals to be drawn (stretched) into thin wires is called ductility. Generally, wires are made up of Iron, Copper and Aluminium. Gold and Silver are the most ductile metals.

Exception : Sodium, Potassium and Calcium are not ductile while Sn and Pb are less ductile.

For Example : 1 g of Gold can be drawn (stretched) into a very fine thin wire of about 2 kilometer.

Copper and Aluminium are also very ductile, and therefore, these can be drawn into thin wires which are used in electrical wiring. Non-metals are not ductile i.e., it can not be drawn into thin wire (due to brittleness). They are easily snapped on stretching.
For Example : Sulphur, Phosphorus and Coal when stretched, all of these are broken into small pieces and do not form thin wire.
Thus non-metals can not show this property.

5. Conductivity :

The property of metal by which heat and electric current flow through them is called conductivity.

Metals are good conductor of heat and electricity, because their atoms contain free electrons which conduct electric current and heat. For example silver, copper and aluminium. Silver is the best conductor of heat and electricity. Copper metal is the next best conductor of electricity. Since silver metal is expensive, So copper and aluminium are commonly used for making electric wire.

Non-Metals are bad conductor of heat and electricity, due to lack of free electrons in their atoms.

Exception : Graphite is good conductor of heat & electricity due to the presence of one free electron in each carbon atom.

To show that metal is a good conductor of heat.

Experiment : Take a small aluminium wire and clamp it on a stand as shown in fig. as below. Then fix a pin to the free end of the wire with the help of wax.
Now, heat the aluminium wire with a candle or burner near its clamped end.

Observation : After some time the other end also becomes hot, wax melt and the pin falls down.

Result : This shows that metals are good conductor of heat. This experiment also shows that metals have high melting point (on over heating, the Al wire do not melt).

We can repeat this activity with copper or Iron metal also but results are same.

Activity
To show that metal is a good conductor of electricity.

Experiment : Take a dry cell, a bulb fitted in a holder, connecting wire which consists of copper wire, crocodile clips and a switch. Set up all apparatus & electric circuit as shown in fig.

Observation : The bulb glows at once when switch is on.

Result : The above activity shows that metals are good conductor of electricity.

6. Sonorous : The property in which metals produce a ringing sound when hit with an object is called sonorous. Metals are sonorous but non-metals are non sonorous i.e., when struck with a hammer they do not produce sound.

Q. Which element is the hardest natural occuring substance ?

Q. Name two metals which are soft & can be cut with knife ?

Q. Give one example of metal which is liquid at room temperature ?

Q. Give one example of non-metal which conduct electricity ?

Q. Write the name of three metals which are not ductile ?

7. Lustrous :
Most of the metals have metallic lustre (shine) and they can be polished. The shining appearance of metal is known as metallic lustre.

For Example : Gold, Silver and Copper metals have metallic lustre (Chamak) and they can be polished. The shiny appearance of metals make them useful for making jewellery and decoration pieces. For example gold and silver are used for making jewellery due to their shining and brightness. The shiny appearence of metals make them good reflectors of light. Silver metal in an excellent reflector of light. So, it is used in making mirror.
Non-metals are not lustrous and not be polished.

Exception : Graphite (allotrope of C) and iodine are lustrous non-metal.

8. Densities :

Metals are very heavy and they have very high densities (except sodium and potassium metals which have low densities).

For Example : The density of mercury is very high (13.6 g/cm3)
Non-metals are light substances, so they have low densities.
For Example : The density of sulphur is 2 g/cm3 which is quite low.
Exception : Iodine and Diamond have high densities.
The smaller metal atom has the lesser density. Osmium(Os) has maximum density (22 g/cm3) among all elements.

9. Melting and Boiling Point : Most of the metals have high melting and boiling points (Except : Sodium and Potassium).

For Example : The melting point of tungsten metal is 3410°C, which is very high. Therefore it is used in filament of electric bulbs.
Non-Metals have generally low melting and boiling points.

Exception : Diamond, which is the allotrope of carbon has very high melting point (3730°C) other exceptions are carbon, boron and silicon which have very high melting points.

10. Colour : Most of the metals are white or silvery grey in colour. Exceptionally, gold has a yellow colour and copper has a reddish brown. Non-metals are generally colourless gases.

Exceptionally chlorine is greenish yellow colour gas, bromine is brown liquid and iodine is violet colour solid.

The important chemical properties of metals and non-metals are discussed below :

1. Reaction with Oxygen :
All the metals react with oxygen to form metal oxides. Which are basic in nature (Except Al2O3 and ZnO, These oxides show basic as well as acidic behavior and are known as amphoteric oxide) and some of them react with water to form alkaline solution, which turns red litmus paper blue.
For Example : Sodium metal reacts with oxygen of air to form basic oxide called sodium oxide
4Na + O₂ ⎯⎯→ 2Na₂O
Sodium oxide
It reacts with water to give an alkali called sodium hydroxide. It turn red litmus paper blue.
Na₂O + H₂O ⎯⎯→ 2NaOH
Sodium hydroxide

Similarly potassium also react with O2 of air and form basic oxide called potassium hydroxide.
4K + O₂ ⎯⎯→ 2K₂O
K₂O + H₂O ⎯⎯→ 2KOH
Since sodium & potassium metals are highly reactive that they react vigorously with the oxygen (of air). They catches fire and start burning when kept open in the air. In fact, K and Na metals are stored in kerosene to prevent their reaction with the oxygen, moisture and CO2 of air.
The reactions of metals and non-metals with O2 is clear by the following activity.Activity 1.6
The experiment to show that metals and non-metals react differently with oxygen.
Experiment : Take a small piece of magnesium ribbon and hold it with a pair of tongs & burn it over the flame of burner.
Observation : Magnesium ribbon burns with brilliant light and converted into solid residue called ash. Collect this ash in a breaker and add some water.
Now, dissolve it by stirring and test the solution with both (blue and red) litmus papers.
Result : The red litmus paper becomes blue but blue litmus paper remains unaffected.
This shows that the solution is basic or alkaline.
2Mg(s) + O2(g) ⎯⎯→ 2MgO(s)
MgO(s) + H2O(l) ⎯⎯→ Mg(OH)2(aq)
Mg(OH)2(aq) + Red litmus ⎯⎯→ Blue

Now, take a small amount of sulphur, powdered in a deflagrating spoon and heat it on a burner flame, till it catches fire. Then introduce the spoon into a gas jar. After burning add some water to the gas jar and shake it well. 
Observations: Test the solution with both (blue and red) litmus papers. The blue litmus paper becomes red and red litmus do not affected.
This shows that aqueous solutions of SO2 is acidic in nature.
S(s) + O2(g) ⎯⎯→ SO₂(g) ; 2SO₂ + O₂ → 2SO₃
SO₃(g) + H₂O() ⎯⎯→ H2SO4(aq)
H₂SO₄(aq) + Blue litmus ⎯⎯→ Red 

Similarly, Iron reacts with oxygen of moist air to form a brown layer of iron oxide (rust) on its surface.
3Fe + 2O2 ⎯⎯→ Fe3O4
                     Iron oxide

When iron is exposed to moist air, a reddish-brown coating of a mixture of ferric oxide (Fe2O3) and ferric hydroxide [Fe(OH)3] is deposited on the surface of the metal. This reddish-brown coating is known as rust, and this process is known as rusting.

Q. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas ?
(b) Write down word equations of all the reactions taking place in this process.
Ans.(a) Add 10 ml water in the test tube and check it with red and blue litmus paper. No change in the colour of red litmus paper. Blue litmus is changed to red. It shows that the gas evolved is acidic in nature.
Ans.(b) Carbon + Air → Carbon dioxide.
Carbon dioxide + water → Carbonic acid
Activity 1.7 : To show the nature of rust (iron oxide)
Experiment : Take a spoonful of rust and dissolve it in a very little amount of water and shake it well Observation : Test the solution with red and blue litmus papers. The red litmus paper becomes blue but blue litmus do not affected. 

Gold, platinum and silver do not react with oxygen (Air), they are called noble metals or native metals.
Non-metals, react with oxygen to form acidic or neutral oxides.
Acidic Oxides : The oxides of carbon, sulphur and phosphorus are acidic, which dissolve in water to form acid and they turn blue litmus paper red.
For Example : Carbon reacts with oxygen of air to form carbon dioxide gas which dissolves in water to form an acid which is called carbonic acid.
C(s) + O2(g) ⎯⎯→ CO2(g)
CO₂(g) + H₂O(l) ⎯⎯→ H₂CO₃(aq)
                              carbonic acid
When phosphorus is burnt in air, phosphorus pentoxide is formed which dissolve in water to form phosphoric acid.
P4(s) + 5O₂(g) ⎯⎯→ 2P₂O5 (s)
                         Phosphorous pentoxide
2P₂O₅(s) + 6H₂O (l) ⎯⎯→ 2H₃PO₄
                                 Phosphoric acid

Neutral Oxides : Those non-metallic oxides which have no action on any type of litmus papers are known as neutral oxides.
For example : Carbon monoxide (CO), water (H2O), Nitric oxide (NO), and Nitrous oxide (N2O).
2. Reaction with water :
The reaction of a metal with water depends on a chemical reactivity. Some metals react with cold water, some react with hot water. Some react only with steam whereas others do not react.
Sodium react with water vigorously along with evolution of H2 gas and heat. After reaction the solution formed (NaOH) is basic in nature.
(i) 2Na + 2H2O ⎯⎯→ 2NaOH + H2
(ii) Magnesium reacts very slowly with cold water but reacts rapidly with boiling water to form magnesium oxide and hydrogen gas.
Mg + H2O ⎯⎯→ MgO + H2
(Boiling water)
This reaction shows that magnesium is less reactive than sodium.
(iii) Zinc reacts rapidly only with steam to form zinc oxide and hydrogen.
Zn + H2O ⎯⎯→ ZnO + H2O
                        zinc (steam)
This reaction shows zinc is less reactive than magnesium.
(iv) When steam is passed over red hot iron, iron oxide is formed and H2(g) is evolved.
(i.e. iron is less reactive metal)
3Fe + 4H2O → Fe₃O₄ + 4H₂
               (steam) Iron oxide

(v) less reactive metals such as Pb, Cu, Ag, Au etc. do not displace hydrogen from water.
Base on the chemical reactions, the metals can be arranged in the order of decreasing reactivities, known as reactivity (or activity) series of metals. Thus, we have
K > Ba > Ca > Na > Mg > Al > Zn > Fe > Ni > Sn > Pb > H2 > Cu > Hg > Ag > Pt > Au
(Most reactive) (Least reactive)
Non-metals do not react with water or steam to evolve hydrogen gas. Because non-metals can not give electrons to reduce the hydrogen ions of water to hydrogen gas.

3. Reactions with Acids :
Non-metals do not react with acids but highly reactive metals react with acids and produce hydrogen gas that burns with a 'pop' sound. Only less reactive metals such as copper, silver, gold etc. do not liberate hydrogen gas from dilute hydrochloric (HCl) and dilute sulphuric acid (H₂SO₄).

For Example :
(i) Sodium is highly reactive metal which react violently with dilute HCl acid to form sodium chloride and hydrogen gas.
2Na(s) + 2HCl(aq) ⎯⎯→ 2NaCl(s) + H₂(g)

Similarly,
2Na(s) + H₂SO₄(aq) ⎯⎯→ Na₂SO₄(aq) + H₂(g)
Sodium sulphate
(ii) Magnesium reacts quite rapidly with dil. HCl and dil H2SO4, forming MgCl2 and MgSO4 and hydrogen gas.
Mg(s) + 2HCl (aq) ⎯⎯→ MgCl2(aq) + H2(g)
                                   Magnesium chloride

Mg(s) + H2SO4(aq) ⎯⎯→ MgSO4 + H2(g)
                                Magnesium sulphate
Similarly,
(iii) Zn(s) + 2HCl (aq) ⎯⎯→ ZnCl2 + H2 (g)
                                         Zinc chloride

Zn(s) + H2SO4(aq) ⎯⎯→ ZnSO4 + H2
                                     Zinc sulphate

Zinc is less reactive than magnesium.

(iv) 2Al(s) + 6HCl (aq) ⎯⎯→ 2AlCl3 (aq) + 3H2
       Aluminium                       Aluminium chloride

2Al(s) + 3H2SO4(aq) ⎯⎯→ Al2(SO4)3 (aq) + 3H2(g)
                                         Aluminium sulphate

(v) Iron reacts slowly with dilute HCl or H2SO4 to give hydrogen.
Fe(s) + 2HCl (aq) ⎯⎯→ FeCl2(aq) + H2(g)
                          Ferrous chloride Iron (II) chloride
Fe(s) + H2SO4 (aq) ⎯⎯→ FeSO4(aq) + H2(g)
                                Ferrous sulphate Iron (II) sulphate

(vi) Copper does not react with dilute HCl/H2SO4 acids.
Cu(s) + HCl(aq) ⎯→ No reaction
Therefore, the reactivity order of metals with acid is
Na > Mg > Zn > Al > Fe > Cu
Non-metals do not react with dilute acids.
A To study the reactivity of metals & non metals towards different acids at room temperature & on warming Experiment : Take samples of metals non metals listed in following table in separate test tubes and label them as A, B, C, D, E & F. With the help of a dropper add 5 drops of dil HCl to each test tube & observe the reaction carefully. If no reaction occurs in the cold solution, warm the test tube gently. Bring a burning matchstick near the mouth of each test tube. Repeat the same activity using dilute sulphuric acid instead of the dilute hydrochloric acid. Record observations. 

Conclusion :
(i) When metals & non metals reacts with acids, there is difference in reactivity. Magnesium is more reactive than aluminium & aluminium is more reactive than iron. Copper do not react with dilute H2SO4 even on heating. Copper reacts with sulphuric acid. The reactivity order is Mg > Al > Fe > Cu
(ii) Non-metals do not react with acids.
(iii) On warming rate of reaction increases.
(iv) When acid react with metal hydrogen gas is evolved out.

Q. One day Reeta went to a jeweller's shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight

4. Reaction with Bases :
Some metals react with alkalis such as sodium hydroxide (NaOH) to produce hydrogen gas.
To show that metals produces H2(g)

Experiment : Take a clean test tube and prepare a fresh solution of sodium hydroxide by dissolving 3–4 pellets of it in 5 ml of water. Then, drop a piece of aluminium foil into the test tube. Now, bring a burning match stick near the mouth of the test tube.

Observation : Pop sound is produced which indicates the presence of hydrogen gas.

Result : This activity shows that hydrogen gas is evolved, when metals react with alkali.
The equation of this reaction is given below –

5. Displacement Reaction :
When a more reactive metal is placed in a salt solution of less reactive metal, then the more reactive metal replaces the less reactive metal from its salt solution. This reaction is called
displacement reaction.
For Example : When a strip of zinc metal is put in the blue colour of copper sulphate solution. After few time the blue colour of the solution fades and red colour copper metal deposited on the zinc strip.
CuSO4 + Zn ⎯⎯→ ZnSO4 + Cu
 copper sulphate zinc sulphate
 (blue) (colourless)
Thus, zinc is a more reactive metal which easily displaces copper from its solution.
CuSO4 + Fe ⎯⎯→ FeSO4 + Cu
(copper sulphate) (iron) (ferrous sulphate) (Copper)
FeSO4 + Cu ⎯⎯→ No reaction
A more reactive non-metal displaces a less reactive non-metal from its salt solution.
For Example : When chlorine gas is passed through a solution of sodium bromide then bromine gas is liberated.
But bromine cannot displace chlorine from its salt solution (NaCl)
NaBr (aq) + Cl2(g) ⎯⎯→ 2NaCl (aq) + Br2(g)
NaCl (aq) + Br2(g) ⎯⎯→ No reaction
Thus, chlorine is more reactive than bromine.

Q. Why aluminium foils are used to wrap food items?
Q. Why immersion rods for heating liquids are made up of metallic substances?
Q. Why copper cannot displace zinc from its salt solution?
Q. Why sodium and potassium are stored in kerosene?
Q. Can you store lemon pickle in an aluminium utensil? Explain –

Uses of Metals and Non-metals :
Uses of Common metals :
(1) Gold, silver and platinum are used in making jewellery.
(2) Zinc is used for galvanization of iron to protect it from rusting.
(3) Iron is used in making machines.
(4) Copper is used in making electric wires.
(5) Aluminium is used in cooking utensils wrapping material, aeroplanes, ships, cars and thermite process.
(6) Metals such as titanium, chromium, manganese, zirconium etc. play an important role in the country's economy and defence. So, these metals are known as strategic metals. These metals and their alloys are used in atomic energy, Space science projects, jet engines, high grade steels and defence equipment. 
(7) Some metals play an important role in the functioning of living systems in animals and human beings. Iron is a constituents of haemoglobin in blood which carries oxygen. Magnesium is present in chlorophyll of green leaves.

Some important uses of Non-Metals :
(1) Non-metal such as oxygen plays very important role in our daily life.
(2) Sulphur is used in the manufacture of sulphuric acid, antiseptic skin ointments and in the rubber industry (for the vulcanization of rubber).
(3) Graphite is used as a dry lubricant.
(4) Phosphorus is used in fertilizers to enhance the growth of plants and it also used in crackers.
(5) Chlorine tablet and bleaching powder are used in water purification process.
(6) Hydrogen and oxygen can be used for cutting and welding metals as oxy-hydrogen flame.
(7) Iodine (Purple coloured solution) which is applied on wounds as antiseptic.
(8) Hydrogen is also used in hydrogenation of vegetable oils (Vegetable ghee). 

METALLURGY FOR COMPETITIVE EXAMINATION

MINERALS AND ORES
Minerals : Minerals are those substances which are obtained from mines. Almost all the metals are found in the form of different compounds in earth crust which are extracted by mining.
Ores : The natural occurring minerals, from which metals can be extracted commercially and economically are known as ores. Therefore it can be stated that all ores are minerals but all minerals are not ores because commercial extraction of metal is not possible from all the minerals. Ores contains higher quantity of certain metals and due to this reason extraction of metal is possible.
Ex : In earth crust aluminum is found as two minerals bauxite and sand, out of these minerals aluminium is extracted economically from bauxite (Al2O3·2H2O) than from sand (Al2O3 · 2SiO2·2H2O). Therefore bauxite is considered as an ore of aluminium, although both sand and bauxite are its minerals.
The process of extraction of pure metal from its ore is called as metallurgy. The process of metallurgy depends upon the nature of ore and the types of impurities present in it, therefore there is not a universal method for extraction of all metals. For each metal different methods of extraction are used.

General steps involved in metallurgical process are as follows :
(i) Grinding or ore,
(ii) Concentration of ore,
(iii) Conversion of concentrated ore to metal oxide.
(iv) Reduction of metal oxide,
(v) Purification of metal.

METALLURGY OF COPPER
• Ores of copper : Copper is found in free state embedded in rocks. In combined state main ores of copper are as follows : 

• Extraction of Copper : Extraction of copper depends on the type of ore.
(A) From free copper : Rocks of copper, found in nature are broken up into small pieces with the help of crushers finely divided powder is passed through stream of water than impurities i.e. are washed away with stream of water and non remaining copper is method and falled in frames, on cooling these copper block are taken out.

(B) From oxide or carbonate ore :
(i) The powdered ore is treated with dilute sulphuric acid to obtain copper sulphate solution. On electrolysis copper metal is obtained.
(ii) The oxide and carbonate ores are finely grinded and calcinated. Due to this moisture and CO2 is removed from oxide. The oxides, so formed is mixed with coke, heated in a reverbatory furnance and reduced to copper metal.

(C) From sulphide ores : The main important ore of copper is sulphide ore or copper pyrites 78% of the total production of copper in world is extracted from these ores.
The extraction process for copper pyrites and copper glance is similar.

Different steps involving in it are as follows :

(i) Grinding of ore : In crushers ores are grinded (broken) into smaller pieces and with the help of stamp mill they are converted into fine powder. 

(ii) Concentration : Concentration of ore is done by froth floatation method. Powdered ore is mixed with pine oil and agitated by a blowing air due to which froth is produced in large amount. The particles of copper sulphide are concentrated on the surface in the froth and stones, sand etc. settled down at the bottom. Froth is collected in another tank where particles of copper sulphide settle down. 

(iii) Roasting : Concentrated ore is roasted in presence of air in the reverbatory furnaces. In this sulphur dioxide is produced. Some part of copper and iron sulphides are converted into oxides, with copper pyrite some amount of arsenic and antimony are found. Oxides of arsenic and antimony are volatiole and so in, reverberatory furnace they are removed as vapours. Copper pyrites, on roasting, is converted into cuprous sulphide and ferrous sulphide.
2CuFeS2 + O2 ⎯→ CuS + 2FeS + SO2
These sulphides are partially oxidised into cuprous oxide and ferrous oxide.
Cu2S + 3O2 ⎯→ 2Cu2O + 2SO2
2FeS + 3O2 ⎯→ 2FeO + 2SO2
So in this way roasted ore contains has Cu2S, FeS, FeO, CuO and SiO2 (in little quantity).

Smelting : Roasted ore is mixed with coke and silica and smelting is done is blast furnace. The height of the furnace is 15 to 20 feet and the diameter is 3 to 5 feet. The blast furnace is made up of steel and lined inside with fire proofbricks. There is jacket surrounding the furnace in which hot water flows. When a stream of hot air is blown through tuyeres fixed at the lower part of furnace, the combustion of coke takes place. During smelting cuprous and ferrous sulphide reacts to form ferrous oxide and cuprous sulphide.
Cu2O + FeS ⎯→ Cu2S + FeO
The FeO, so obtained reacts with silica to form ferrous silicate (FeSiO3).
FeO + SiO2 ⎯→ FeSiO3
Ferrous oxide Silica Ferrous silicate (slag)
Ferrous silicate is fusible and known as slag. Due to light weight it collects on the surface of metal and removed through a small opening in the furnace. In molten matte FeS and CuS are present in fused state, this liquid is called as copper matte.

(iv) Production of blister copper : (Bassemer process)
Copper matte is transfered from the blast furnace to the bassemer converter. Copper sulphide is oxidized to cuprous oxide which reacts with copper sulphide and converts into copper metal.
Cu2S + 2Cu2O ⎯→ 6Cu + SO2

Copper, in the melted state is poured into sand frames.
On cooling dissolved SO2 released due to which blisters are formed on the surface of metal, so this copper is known as blister copper. It contains nearly 98 percent copper. 

(v) Refining of copper :
(a) Polling : In blister copper some metal oxides are present in small quantity. To purify this blister copper is fused (melted) and is churned with logs of green wood. The gaseous hydrocarbon present in logs of green wood reduces copped oxide to copper.
(b) Electrolytic refining : Pure copper is obtained by electrolytic refining process. Acidic copper sulphate is taken in an electrolytic cell, impure copper rod act as an anode while the pure copper rod act as a cathode. On providing electric current pure copper is collected on cathode while the impurities remains at the anode as anode mud. Copper obtained by this method is nearly 100 percent pure.

• Extraction of iron : This metal is found mainly in the form of oxides. For its extractor mainly or carbonate ores are used process is completed in following steps.

(i) Grinding of ores : With the help of crusher ores, obtained from mines, are crushed into small pieces afterwards with the help of stamp mill, it is converted into fine powder.

(ii) Concentration : concentration of ore is done by magnetic separation method.  

(iii) Roasting : Concentrated ore is subjected to roasting process in a reverberatory furnace carbon, phosphorus, sulphur arsenic etc. are present as impurities. Due to roasting the volatile substances like sulphur dioxide, phosphorus penta oxide and oxide of antimony and arsenic are removed from the ores and due to excess of roasting ferrous oxide is converted into ferric oxide.

(iv) Smelting : Smelting of roasted ore is done in blast furnace. Blast furnace plays a very important role in the metallurgy of iron. For this process, blast furnace of 80-100 feet height and internal diameter of 20-25 feet is used.
From top of the furnace charge (iron ore, coke and small amount of lime stone) is introduced. The temperature of the furnace have increase from top to bottom. Tuyeres are present from which hot air is blown due to which coke on combustion produces carbon monoxide, which converted ore into metal.
Fe2O3 + 3CO ⎯→ 2Fe + 3CO2

Thus iron is collected a bottom and impurities of silica, carbon and phosphorous get dissolved in it.  

Function of limestone (CaCO3) : Due to the action of heat, limestone decomposes to calcium oxide and carbon dioxide.

(limestone) (calcium oxide)
The silica impurity of the iron ore reacts with the calcium oxide obtained from lime stone to form molten calcium silicate, reffered to as slag.

Molten slag floats over molten iron at the bottom of the furnace.
As extraction proceeds, more and more limestone, ore and coke are fed into the top of the furnace and the molten slag and iron are tapped off at the bottom.
The iron obtained from the blast furnace is called cast iron or pig iron. It is brittle due to the presence of large amounts of carbon and other dissolved impurities.

COMMERCIAL FORMS OF IRON
There are three different commercial forms of iron. They are cast iron, wrought iron and steel.
Cast iron : Cast iron is the cheapest form of iron. It contains 2.5-5% carbon and other impurities like sulphur, silicion, phosphorus, etc. It is brittle and has a low tensile strength. It rusts easily. It is used to make articles like manhole lids, radiators, railings, etc, and in making steel.
Wrought iron : It is the purest form of iron containing about 0.2% carbon. It is malleable and ductile but has low tensile strength than steel It can be welded and does not rust easily. It is used to make cores of electromagnets, iron nails, pipes, bolts, gates, etc.
Steel : Steel is an alloy of iron with 0.1-1.5% of carbon. It is prepared by mixing molten iron with scrap iron and limestone. The charge is heated in an oxygen converter and oxygen is blown into the molten mixture. Limestone converts the impurities into slag and most of the carbon escapes as carbon dioxide.  

Flow chart for the extraction of iron
ALUMINIUM
Aluminium is the most abundant element in the earth's crust. The important ores of aluminium are –
(i) Bauxite – Al2O3 . 2H2O (ii) Corundum – Al2O3 (iii) Cryolite – Na3AlF6 (iv) kaolin – Al2Si2O7 .2H2O
Aluminium is chiefly extracted from bauxite ore.
• Crude bauxite is crushed, ground, dried and heated with concentrated caustic soda solution (naOH). Bauxite dissolves in NaOH forming sodium aluminate solution. The undissolved impurities are filtered off. 

• Sodium aluminate solution is diluted with water and treated with a little aluminium hydroxide to cause precipitate formation. Hydrolysis takes place and a white precipitate of Al(OH)3 is formed.   

• The aluminium hydroxide precipitate is filtered, washed, then heated to get pure aluminium oxide (alumina). 

• Electrolytic reduction of alumina
Aluminium is extracted from alumina by electrolysis. Alumina (Al2O3) is mixed with a calculated quantity of cryolite (Na3AlF6) and melted in an iron cell. Pure alumina melts at 2045°C. So, cryolite is added to lower its melting point.
The iron cell is lined with carbon, which acts as the cathode. Graphite rods acts as the anode. Electric current is passed through the circuit (Fig). Molten aluminium is liberated at the cathode and sinks to the bottom of the cell from where it is removed. Oxygen gas is liberated at the anode. 

As the metal is removed, fresh amounts of pure alumina are added. The anode has to be replaced from time to
time, because oxygen gas attacks the graphite anodes and eats them away.
Uses of aluminium
1. It is used for making electrical wires and cables.
2. It is used as a reducing agent in metallurgy.
3. It is used for making cooking utensils, foils, saucepans, TV aerials, ships, aeroplanes and even space rockets.
4. It is used for making silver paints and mirros.
5. It is used in making alloys, such as duralumin and magnalium, which are used for making aircraft bodies.

DO YOU KNOW
Thermit Welding
Aluminium and iron are involved in competition reaction to repair railway tracks. Aluminium and iron (III) oxide are being heated together, to give molten iron. This is run into gaps between railways lines. The process iscalled thermit welding.

Quick Revision
 Metal and non-metal elements are classified according to their physical and chemical properties.
 Reactive metals do not naturally ocur in their pure state.
 Gold and platinum are non-reactive, as such occur in their pure from.
 Metals are malleable, ductile and have lustre, high specific gravity and refractivity to light.
 Metals are good conductor of heat and electricity.
 All metals are solid except mercury, which is a liquid.
 Metals have mostly high melting point.
 Tungsten has high tensile strength.
 Non-metals are mostly poor conductor of heat and electricity.
 Non-metals have generally low melting point.
 Gallium has very low melting point and seven melts in hand.
 Iodine is denser than many metals.
 Sodium is very soft and can be cut by a knife.
 Graphite though being a non-metal, is a good conductor of electricity.
 When metallic magnesium is burnt, it forms basic oxide, white non-metallic sulphur forms acidic oxide.
 Most metals when burnt combine with oxygen to form basic oxides and non-metals form acidic oxides.
 Most metals when burnt combine with oxygen to form basic oxides and non-metals form acidic oxides.
 Copper is non-magnetic while iron is magnetic.
 Gold and platinum do not react with air, water and acids, thus called 'noble metals'.
 Sodium is very reactive in air, therefore, kept in kerosene.
 Sodium reacts with cold water to form sodium hydroxide and hydrogen.
 Magnesium reacts violently with steam but mildly with cold water.
 Most metals react with acids to form salts and hydrogen.
 Copper cannot displace iron in iron compounds.
 Iron, magnesium and zinc are more reactive than copper.
 More reactive metals have high tendency to form compounds.
 More reactive metals displace less reactive metals form their salt solutions, but less reactive metals cannot displace more reactive metals.
 Titanium is highly resistant to corrosion and is very strong.
 Some metals react with acids (hydrochloric acid) and displace the hydrogen atom from their molecules.
 Air and water or moisture are necessary for corrosion to take place.

Question. Which is the most reactive metal of the following ?
(A) Copper
(B) Sodium
(C) Calcium
(D) Iron
Answer : B

Question. Malleability is the characteristic property of :-
(A) Silver
(B) Mercury
(C) Plastic
(D) Potassium
Answer : A

Question. Which of the following can be beaten into thin sheet:-
(A) Coal
(B) Phosphorus
(C) Aluminium
(D) Sulphur
Answer : C

Question. Sulphur dioxide (SO2) is :-
(A) Acidic oxide
(B) Basic oxide
(C) Neutral oxide
(D) None of these
Answer : A

Question. Which of the following is a property of non-metals?
(A) Low melting points
(B) Poor conductor of electricity
(C) Low densities
(D) All of these
Answer : D

Question. The non-metals having shining surface is :-
(A) Carbon
(B) Sulphur
(C) Iodine
(D) Phosphorus
Answer : C

Question. Carbon monoxide is a/an :-
(A) Acidic oxide
(B) Basic oxide
(C) Amphoteric oxide
(D) Neutral oxide
Answer : D

Question. Which among the following elements is metalloid:-
(A) Beryllium
(B) Barium
(C) Boron
(D) Bismith
Answer : C

Question. The metal which is soft and can be cut with a knife is :-
(A) Zinc
(B) Copper
(C) Sodium
(D) Magnesium
Answer : A

Question. Which metal is found in the liquid state at room temperature ?
(A) Zinc
(B) Magnesium
(C) Calcium
(D) Mercury
Answer : D

Question. The metal which can replaces copper from its salt solution is :-
(A) Silver
(B) Mercury
(C) Zinc
(D) Gold
Answer : C

Question. The metal which does not react with air :-
(A) Sodium
(B) Calcium
(C) Gold
(D) Aluminium
Answer : C

Question. Which of the following is best conductor of heat and electricity :-
(A) Silver
(B) Copper
(C) Aluminium
(D) Iron
Answer : A

Question. The non-metal which is liquid at room temperature is :-
(A) Chlorine
(B) Fluorine
(C) Bromine
(D) Iodine
Answer : C

Question. Antimony and arsenic are category of ...... :-
(A) Metal
(B) Non-metal
(C) Metalloid
(D) Mineral
Answer : C

Question. Who classified the elements in metals and non-metals?
(A) Lavoisier
(B) Priestley
(C) Lemaitre
(D) Lenoir
Answer : A

Question. Which of the following metals occur in their pure state?
(A) Copper
(B) Iron
(C) Zinc
(D) Gold
Answer : D

Question. Which of the following metals is liquid at room temperature?
(A) Sodium
(B) Mercury
(C) Zinc
(D) Aluminium
Answer : B

Question. Which of the following is a good conductor of heat?
(A) Bromine
(B) Chlorine
(C) Mercury
(D) Iodine
Answer : C

Question. Which of the following non-metals occurs as liquid?
(A) Bromine
(B) Sulphur
(C) Iodine
(D) Carbon
Answer : A

Question. Which of the following non-metals occurs as a solid?
(A) Sulphur
(B) Carbon
(C) Iodine
(D) All of the above
Answer : D

Question. Which of the following non-metal occurs as a gas?
(A) Nitrogen
(B) Chlorine
(C) Both the above
(D) None of the above
Answer : C

Question. Which of the following metals has very low melting point and melts even in hand?
(A) Sodium
(B) Gallium
(C) Potassium
(D) Graphite
Answer : B

Question. Which of the following is lighter than water?
(A) Potassium
(B) Sulphur
(C) Iodine
(D) Graphite
Answer : A

Question. Which of the following is denser than many metals?
(A) Bromine
(B) Chlorine
(C) Sulphur
(D) Iodine
Answer : D

Question. Which non-metal is a good conductor of electricity?
(A) Bromine
(B) Iodine
(C) Graphite
(D) Chlorine
Answer : C

Question. Magnesium oxide is –
(A) Basic oxide
(B) Acidic oxide
(C) Neutral oxide
(D) None of these
Answer : A

Question. Sulphur dioxide is –
(A) Basic oxide
(B) Acidic oxide
(C) Neutral oxide
(D) None of these
Answer : B

Question. Which of the following is a noble metal?
(A) Copper
(B) Iron
(C) Gold
(D) Aluminium
Answer : C

Question. When medium reacts with cold water, it forms –
(A) Sodium hydroxide and oxygen
(B) Sodium hydroxide and hydrogen
(C) Sodium hydroxide and carbon dioxide
(D) None of these
Answer : B

Question. Which of the following is very reactive and kept in kerosene?
(A) Iodine
(B) Bromine
(C) Sodium
(D) Potassium
Answer : C

Question. Which of the following reacts violently with steam?
(A) Iron
(B) Zinc
(C) Magnesium
(D) None of these
Answer : C

Question. Which metal reacts with dilute hydrochloric acid to produce hydrogen?
(A) Zinc
(B) Copper
(C) Iron
(D) Platinum
Answer : A

Question. When iron nail reacts with copper sulphate solution, the reaction is called –
(A) Displacement reaction
(B) Replacement reaction
(C) Reduction reaction
(D) None of these
Answer : A

Question. When iron nail is placed in copper sulphate solution, the bluish colour of copper sulphate turns –
(A) Brownish
(B) Yellowish
(C) Greenish
(D) Colourless
Answer : C

Question. When zinc is put in copper sulphate solution, the colour of copper sulphate becomes –
(A) Greenish
(B) Yellowish
(C) Brownish
(D) Colourless
Answer : D

Question. Which of the following can be beaten into thin sheets?
(A) Zinc
(B) Phosphorus
(C) Sulphur
(D) Oxygen
Answer : A

Question. Which of the following statements is correct?
(A) All metals are ductile
(B) All non-metals are ductile.
(C) Generally, metals are ductile.
(D) Some non-metals are ductile.
Answer : C

Question. Which metals have tendency to form compounds?
(A) More reactive metals
(B) Less reactive metals
(C) Both the above
(D) None of these
Answer : A

Question. Corrosion is a –
(A) Reduction reaction
(B) Oxidation reaction
(C) Redox reaction
(D) Displacement reaction
Answer : B

Question. Which of the following is a magnetic metal?
(A) Copper
(B) Aluminium
(C) Iron
(D) All the above
Answer : C

Question. Which of the following is highly resistant to corrosion?
(A) Iron
(B) Copper
(C) Aluminium
(D) Titanium
Answer : D

Question. The non-metal which is used for the manufacture of fertilizers is :-
(A) Chlorine
(B) Sulphur
(C) Phosphorus
(D) None of these
Answer : C

FILL IN THE BLANKS

Question. Iron is ................. reactive than copper.
Answer : More 

Question. Metals react with acids to produce ................. gas.
Answer : H2

Question. Copper does not react with ................. acid.
Answer : Dil HCl/H2SO4

Question. ................. is used in crackers.
Answer : Phosphorus

Question. Phosphorus is stored in .................
Answer : Water 

Question. ................. non-metal is catches fire if exposed to air,
Answer : Phosphorus

Question. Sulphurous acid turns ................. litmus paper .................
Answer : Blue, red

Question. When a copper vessel is exposed to moist air for long time. It acquires ................. coating.
Answer : Dull green

Question. Metallic oxides are ................. in nature.
Answer : Acidic 

Question. The iron nail and the aluminium wire ................. on beating.
Answer : Change their shape

Question. Metals are ................. conductors of heat and .................
Answer :  Good electricity

Question. Phosphorus is a very ............... non-metal.
Answer :  Reactive 

Question. Metals are ............... conduc tors of heat and ...............
Answer :  Good, electricity

Question. Iron is ............... reactive than copper.
Answer :  More 

Question. Metals react with acids to produce ............... gas.
Answer :  Hydrogen

MARK 'T' IF THE STATEMENT IS TRUE AND 'F' IF IT IS FALSE

Question. Coal can be drawn into thin wire.
Answer : FALSE

Question. Phosphorous is a very reactive non-metal.
Answer : TRUE 

Question. Aluminium foils are used to wrap food items.
Answer : TRUE 

Question. Calcium is stored in kerosene.
Answer : FALSE

Question. Generally, non-metals react with acid.
Answer : FALSE

Question. Metals can gain electrons to form negative ion.
Answer : FALSE

Question. Platinum can not affected by air and water.
Answer : TRUE 

Question. Metals and non-metals are separated by a zig-zag line.
Answer : TRUE 

Question. Generally, non-metals react with acids.
Answer : FALSE

Question. Sodium is a very reactive metals.
Answer : TRUE 

Question. Copper displaces zinc from zinc sulphate solution
Answer : TRUE 

Question. Coal can be drawn into wires.
Answer : FALSE

MATCH THE FOLLOWING
Math the substances given in column A with their uses given in column B.
      Column–A         Column–B
(A) Gold                (i) Antiseptic
(B) Silver              (ii) Dry lubricant
(C) Aluminium      (iii) Jewellery
(D) Carbon           (iv) Decorating sweets
(E) Mercury          (v) Wrapping food
(F) Copper           (vi) Fuel
(G) Zinc               (vii) Electric wire
(H) Silicon           (viii) Thermometers
(I) Graphite         (ix) Semi-conductors
(J) Sulphur          (x) Galvanisation

Answer : (A) → (iii) ; (B) → (iv) ; (C) → (v) ; (D) → (vi) ; (E) → (viii) ; (F) → (vii) ; (G) → (x) ; (H) → (ix) ; (I) → (ii) ; (J) → (i)

WHICH OF THE FOLLOWING STATEMENT IS CORRECT
(i) All non-metals are ductile.
(ii) Metals are good conductors of heat and electricity.
(iii) Non-metals are used in water purification.
(iv) Hydrogen is a gas that burns with a 'pop' sound.
(v) Phosphorus catches fire, when exposed to air.
(vi) The oxides of non-metals are basic.
(vii) The coal, pencil lead and plastic show the property of malleability.
(viii) The metal produce a ringing sound.
(ix) The oxide of magnesium is acidic in nature.
(x) Metal react with sodium hydroxide to produce hydrogen gas.
(xi) The zinc metal replaces the iron metal from its salt solution.
Answer : 1. (ii), (iii), (iv), (v), (xiii), (x) and (xi)

VERY SHORT ANSWER TYPE QUESTIONS

Question. Which property of metals makes them suitable for use in jewellary ?
Answer : Ductility

Question. Name two non-metals which oxides are acidic in nature.
Answer : Sulphur and phosphorus

Question. Name two oxides which are neutral in nature.
Answer : Carbon monoxide(CO), N2O

Question. Name one non-metal which is liquid at room temperature.
Answer : Bromine (Br)

Question. Name the metal that burns in air with a brilliant white flame.
Answer : Mg

Question. Which is more metallic : Potassium or aluminium ? Give reason.
Answer :  K

SHORT ANSWER TYPE QUESTIONS

1. Give reason for the following :-
(a) Electrical wires cannot be made out of sulphur. Why ?
Answer : (a). Because sulphur is a non-metal. It can not show the property of ductility due to brittleness.

(b) Copper cannot displace zinc from its salt solution. Why ?
Answer : (b). Cu is a less reactive metal than Zn.

(c) Phosphorus is stored in water why ?
Answer : (c). Due to high reactivity.

(d) What happens, when metals react with alkali?
Answer : (d). H2 gas is evolved.

(e) What happens when CO2 is dissolved in water ?
Answer : (e). Carbonic acid is formed.

(f) Metals are electropositive in nature, why ?
Answer : (f). Because metals lose their electrons easily to get inert gas configuration.

(g) Complete the following equation : Na2O + H2O ⎯→
Answer : (h). Na2O + H2O ⎯→ 2NaOH

Question. Give reasons for the following :
(i) Aluminium foils are used to wrap food items
(ii) Immersion rods for heating liquids are made up of metallic substances.
(iii) Copper cannot displace zinc from its salt solution
(iv) Sodium and potassium are stored in kerosene.
Answer. (i) Aluminium is highly malleable metal and it is very easy to make aluminium foil in compare to other metals.
(ii) Immersion rods are made up of metallic substances because metals are good conductors of heat and electricity.
(iii) Copper cannot displace zinc from its solution because zinc is more reactive than copper (i.e., copper is less reactive than zinc.)
(iv) Sodium and potassium metals are very reactive because they react with oxygen and water easily. A lot of heat is produced in the reaction so sodium and potassium are always stored and kerosene.

Question. Can you store lemon pickle in an aluminium utensil? Explain.
Ans. No. this is because acids react with aluminium.

Question. What happens when
(i) Dilute sulphuric acid is poured on a copper plate?
(ii) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Answer. (i) Copper sulphate is formed and hydrogen gas is liberated.
Copper + Sulphuric acid ⎯→ Copper sulphate + Hydrogen (gas)
(ii) Brown coating is deposited on the iron nails. This is because of the displacement of copper from copper sulphate solution by iron.
Iron + Copper Sulphate (solution) ⎯→ Iron sulphate (solution) + Copper

Question. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(i) How will she find the nature of the gas?
(ii) Write down word equations of all the reactions taking place in this process.
Answer. (i) She will bring a wet litmus paper in contact with the gas. If the gas turns wet blue litmus paper into red, the
gas will be acidic.
(ii) (a) Carbon + Oxygen ⎯→ Carbon dioxide.
(b) Carbon dioxide + Water ⎯→ Carbonic acid. (from wet litmus)

Question. One day Reeta went to a jeweller's shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when theybrought the jewellery back, they found that there was slight loss in its weight. Can you suggest a reason for the loss in weight?
Answer. The jeweller dip the jewellery in the solution of acid, which reacts with the outer covering of metals. Thus there is a net loss of weight in the metal of the ornament.

Q6. Define rusting. List the conditions required for rusting. What is the nature of rust.

a. When Iron is exposed to moist air, it develops a reddish brown coating over it which is called as rust. This phenomenon is known as rusting.

b. There are two conditions for rusting to occur - presence of moisture and presence of Oxygen.

c. As rust is hydrated Iron oxide, so it is Basic in nature

Q7. a. What happens when Sulphur dioxide is passed in Water ?

b. When iron fillings are added to Sulphuric acid.

c. When Sulphur powder is mixed with Hydrochloric acid.

Ans: a. Sulphurous acid is formed.

b. iron reacts with Sulphuric acid to form Iron Sulphate and Hydrogen gas is released.

c. No reaction takes place as Sulphur is a non metal.

Q8. Name a non-metal which is used in fetilizers

Ans: Nitrogen

Q9. Why does the colour of Copper Sulphate solution change when Zinc is added to it ?

Ans: Zinc is more reactive metal than Copper so it displaces Copper from its salt solution to form Zinc Sulphate and Copper metal which causes the colour change.

Q1O. Why is Phosphorous stored under water while Sodium and Potassium stored under Kerosene oil.

Ans: Phosphorous is a reactive non metal which reacts with Oxygen but not with water while Sodium and Potassium react explosively with water and also burn in presence of Oxygen, hence stored under Kerosene oil.