Why Are Aluminium And Copper Metals Used For Making Cooking Vessels?
Aluminium and copper metals are good conductor of heat. When exposed to air, these develop a layer of oxide. This makes it resistant to further corrosion.
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Why Is Sodium Kept Immersed In Kerosene Oil?
Sodium is very reactive. If kept exposed to air, it catches fire.
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Distinguish Between Calcinations And Roasting.
Calcination:
(i) The ore is heated is absence of air.
(ii) It is used for carbonate ores.
Roasting:
(i) The ore is heated in the presence of air.
(ii) It is used for sulphide ores.
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Ionic Compounds Have High Melting Point. Why? Give Reason In Support Your Answer.
In iconic compounds, ions are joined together due to powerful electrostatic forces, therefore, considerable energy is required to separate these ions and break the lattice. Thus ionic compounds have high melting points.
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Generally, Ionic Compounds Are Hard Crystalline Solids. Why?
There are solids due to strong force of attraction between oppositely charged ions resulting in the formation of hard crystalline lattice.
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What Are Alloys?
An alloy is a homogeneous mixture of two or more metals, or a metals and a non-metal. It is prepared by first melting the main metal, and then dissolving the required amount of other metals or non-metals. This mixture is then cooled to form an alloy of a given composition.
What Is Meant By Metallurgy?
Metallurgy involves various processes starting with the treatment of ore to getting metals in the pure form.
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Questions For Practice
Question 1:
Compare the properties of a typical metal and non-metal on the basis of the following:
(i) nature of oxide formed by them
(ii) conductivity.
Answer :
(i) Metals from basic oxide, e.g., sodium gives a basic oxide, Na2O. Non-metals from acidic oxide, e.g., sulphur gives an acidic oxide, SO2.
(ii) Metals have good conductivity, e.g., copper is a good conductor. Non-metals do not conduct heat or electricity, e.g., sulphur.
Question 2:
How is an ore different from a mineral?
OR
тАЬall ores are minerals but all minerals are not oresтАЭ. Justify the statement with examples.
Answer 2:
The metals found in nature in combined state are called minerals. If some minerals contain a very high percentage of a particular metal and the metals can be profitably and economically extracted, then it is called an ore.
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Questions From Board Papers
Question 1:
Atmospheric air always contains moisture. Then, how can you protect iron articles from the affect of atmosphere?
Answer 1:
Iron articles can be protected from the effect of atmosphere by painting, oiling and greasing. This gives temporary protection to iron articles. For long time protection, galvanising or chrome plating are quite useful.
Question 2:
Explain, why some metals are more reactive and others less reactive and others less reactive?
OR
What determines the reactivity of metals?
Answer 2:
When metals react, they lose electrons to form positive ions. Such metals which can lose electrons easily to form positive ions when reacted with other substances, are reactive metals. On the other hand, if a metal loses electrons less rapidly to form positive ions, it will reacts slowly with other substances. Such a metal will be less reactive. For example, sodium atom is a very reactive metals because it readily loses one electron, forms a positive ion which then combines with other substances. On the other hand, lead atom loses electrons with difficulty to form positive ions, so lead metal is less reactive.
Important Questions On 10th Science Chapter 3
For example: sodium and potassium.
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Metals that are less reactive than hydrogen do not displace it.
For example: copper and silver.
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Galvanisation: An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and moisture. Hence, rusting is prevented.
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How Are The Metals Different In Reactivity With O2?
(i) Sodium and Potassium react so vigorously if it kept in open it catches fire thatтАЩs why it is kept immersed in Kerosene.
(ii) Magnesium, Aluminium, Zinc, Lead are the metals which covered with a thin layer of Oxide on the surface of it which prevent it from the further oxidation.
(iii) Iron does not burn on heating but iron fillings burn on heating.
How Are The Metals Different In Reactivity With O2?
(i) Sodium and Potassium react so vigorously if it kept in open it catches fire thatтАЩs why it is kept immersed in Kerosene.
(ii) Magnesium, Aluminium, Zinc, Lead are the metals which covered with a thin layer of Oxide on the surface of it which prevent it from the further oxidation.
(iii) Iron does not burn on heating but iron fillings burn on heating.
(iv) Copper does not burn but it is coated with a black copper oxide.
(v) Silver and Gold are the metals which does not react with oxygen because it is very low reactive metal.
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What Happen When Metal React In Air?
Metals combine with oxygen to forms metal oxide.
Metal + O2 тЖТ Metal oxide
For example:
Na + O2 тЖТ NaO2
2Cu + O2 тЖТ 2CuO
K + O2 тЖТ K2O
4Al + 3O тЖТ 2Al2O3
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What Do You Understand By The Amphoteric Oxide?
Amphoteric oxide is a type of metal oxide which react with both acids as well as base.
For example:
Al2O3 + 2NaOH тЖТ 2NaAlO2 + H2O
Al2O3 + 6HCl тЖТ 2AlCl3 + H2O
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What Are The Reaction Of Metal According To The Reactivity Series?
(i) K, Na, Ca react with cold H2O.
(ii) Al, Fe, Zn react with steam.
(iii) Fe, Sn react with hot H2O.
(iv) Pb, Cu, Ag, Au are the metals which does not react with H2O.
(v) Ca and Mg float as bubble H2 stick to their surface.
Examples:
3Fe + 4H2O тЖТ Fe3O4 + 4H2
2Na + 2H2O тЖТ 2NaOH + H2 + Heat
Ca + 2H2O тЖТ Ca(OH)2 + H2
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Properties Of Metals
(i) Metals are lustre and having shinning surface.
(ii) Metals are generally hard except sodium, Lithium and potassium which are soft and it easily cut with a knife.
(iii) Metals always exist in solid state except mercury.
(iv) Metals have the property of malleability it can beaten for the preparation of thin sheet. Gold and silver are the most malleable metal.
(v) Metals have the property of ductility so metals can be preparing into thin wire.
(vi) Metals are good conductor of heat and electricity. For example, silver and copper are good conductor of heat but lead and mercury are poor conductor of electricity.
(vii) Metals have high melting point except sodium and potassium they are very soft metal.
(viii) Metals are sonorous thatтАЩs why metal produce a sound when strike with a hard surface.
(ix) Metals form oxide which is basic in nature.
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What Happen When Metal React With Acids?
When metal react with acid salt and water will produces.
For example:
Fe + 2HCL тЖТ FeCl2 + H2
Mg + 2HCL тЖТ MgCl2 + H2
Zn + 2HCL тЖТ ZnCl2 + H2
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What Happen When A Metal Reacts With Other Metal Salt?
Metal A + Salt of metal B тЖТ Salt solution A + metal B
If a metal is more reactive than so it displaces the less reactive metal.
For example:
Na + HCl тЖТ NaCl + H2
Ca + H2SO4 тЖТ CaSO4 + H2
These two reaction are exothermic.
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What Are Ionic Compound?
Ionic compound are those compound which contain both metal and non-metal ions in this compound strong compound strong force of attraction take place between ions.
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What Are The Properties Of Ionic Compound?
Properties of ionic compound are:
(i) Ionic compound conduct electricity in aqueous solution but it cannot cannot conduct electricity in dry or solid form.
(ii) Physical Nature: It is solid in nature and also very hard because strong force of attraction between the positive and negative ions.
(iii) Melting and boiling: It has high melting point and boiling point.
(iv) It is soluble in water but it does not dissolve in organic solvent like: Petrol, Oil etc.
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What Do You Understand By The Aqua Regia?
It is the only reactant that is capable of dissolving metals like gold and platinum. It is obtained by mixing concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1.┬аAqua Regia┬аis also known as Royal water.
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Properties of Non-Metals
(i) Non-metals are not lustre they do not have shinning surface except iodine.
(ii) Non-metals are generally soft except diamond it is a form of carbon which is the natural hardest natural substance.(iii) Non-metals are existing in solid or gaseous state except bromine.
(iv) Non-metals are non-malleable in nature.
(v) Non-metals are non-ductile.
(vi) Non-metals are poor conductor or heat and electricity except graphite it is a good conductor of heat and electricity.
(vii) Non-metals have low density have having very low melting point.
(viii) Non-metals are not sonorous they do not produce any sound when strike with other object.
(ix) Non-metals forms oxide which is basic in nature.
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What Are Properties Used When A Metal Reacts With Non-Metal?
(i) Reactivity of the element is the tendency to attain a completely filled balanced shell.
(ii) Atom of the metal lose electron from their balance shell to form cation. Atom of the non-metal gain electron in the valence shell to form anion.
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What Are The Steps That Take Place In The Extraction Of Metals?
On the basic of reactivity series we can group the metals into three group:
(i) Metals of high reactivity: For example, potassium, sodium, calcium, magnesium and Aluminium.
(ii) Metals of medium reactivity: For example, zinc, iron, lead etc.
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How Is The Enrichment Of Ores Done?
Ores are generally contaminated with impurities, such as soil, sand, etc., called gangue. These impurities must be removed from the ores before proceeding to extraction. The method used for removing gangue depend upon the physical and chemical properties of the gangue and the ores.
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How Do You Extract Teh Metals With Low Reactivity?
Low reactive are very unreactive. For example, cinnabar(HgS) is an ore of mercury. When heated it is first converted to mercury oxide which on further heating changes to metallic mercury.
2HgS + 3O2 тЖТ 2HgO + 2SO2
2HgO тЖТ 2Hg + O2
Similarly copper which occurs in nature as Cu2S can be obtained by just heating in air.
2CuS + 3O2 тЖТ 2CuS + 2SO2
2Cu2O + Co2S тЖТ 6Cu + SO2
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Occurrence Of Metals
Element of compound which occur naturally in the earth crust known as minerals. Minerals from which metals can be extracted profitably are called ores. Seawater also contain some soluble salts such as Sodium chloride, magnesium chloride, etc.
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What Do You Understand By The Reduction Reaction?
It is a type of process in which a metal oxide are reduced to corresponding metal by using reducing agent like carbon.
ZnO + C тЖТ Zn + CO
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How Do You Extract The Top Element From The Activity Series?
The metals at the higher end of the activity series are very reactive. Their oxide cannot be reduced with carbon because the metal has greater affinity for oxygen than carbon. Such metals are obtained by electrolytic reduction. Sodium, magnesium and calcium are obtained by the electrolytic reduction of their molten chlorides. The metals are obtained at the cathode while chlorine is liberated at the anode.
The reaction may be represent as
Na+ + e- тЖТ Na At cathode
2Cl- тЖТ Cl2 + 2e- At anode
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What Do You Understand By The Thermit Process?
The reaction of iron oxide Fe2O3 with Aluminium is an exothermic process. Iron is obtained in molten state which is used to join railway tracks or cracked machine parts. This reaction is known as thermit reaction and the process is known as thermit process.
Example: Fe2O3 + 2Al тЖТ 2Fe + Al2O3 + Heat
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What Is Meant By Corrosion? State With Example.
The surface of some metal get corrode when they exposed in the contact of moist air for a very long period so this is called corrosion.
For examples:
(i) Silver articles turn black when exposed to air. This is because it reacts with Hydrogen Sulphide in air to form Silver Sulphide which is black.
(ii) Similarly copper articles turn green due to reaction with atmospheric carbon dioxide forming green copper carbonate.
(iii) Iron gets rusted when exposed to moist air from brown oxide of iron.
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The Process Of Electrolytic Refining
In the process of electrolytic refining we use metal such as copper nickel, etc and remove all the impurities and made a new metal. We take two test tube one is thin and other is big and take a dissolve solution of CuSO4 and in a big tube we put impure Cu and provide electricity in it so through the big test tube leave two electrons and it enters in the thin test tube and combine with two other ions that is already present their Cu+2 +2x in the process all the anode mud store at the downward. The impure metal is made the anode and the anode and a thin strip of pure metal is middle at the cathode. A solution of metal salt is used as electrolyte. The apparatus on passing current through the electrolyte the pure metal from the anode dissolve into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposit on the cathode. The soluble impurities go into the solution.
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What Are The Methods Used For The Prevention Of Corrosion?
Rusting of iron metal can be preventing by the following method:
(i) by painting the surface.
(ii) by oiling or greasing the surface.
(iii) galvanizing, chrome plating, anodising or making alloy.
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Explain The Method Of Galvanization?
It is a method of protecting steel and iron from rusting. The article is coated with a thin layer of zinc. Galvanized article is protected against rusting even if coating is broken.
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What Is Meant By The 22-Carat Gold?
Pure gold which is 24-carat gold is very soft and is not suitable for making ornaments. It is alloyed with either copper or silver to make it hard. Generally, in India 22carat gold is good for making jewellery, it means 22 part of gold is alloyed with 2 part of copper or silver.
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What Do You Understand By The Acidic Or Basic Oxide?
Basic oxide: Those oxides which react with acids or acidic oxide to form salt and water are called basic oxide. Metal react with oxygen to form metallic oxide which are generally basic in nature example Na2O (sodium oxide) CaO (calcium oxide) K2O (potassium oxide) MgO (magnesium oxide) are basic oxide.
MgO + 2HCl тЖТ MgCl2 + H2O
Acidic oxide: Those oxides which react which react with bases or basic oxide to form salt and water are called acidic oxides. Non-metals react with oxygen to form non-metallic oxide which are generally acidic in nature example CO2 (carbon dioxide), SO2(Sulphur dioxide), K2O (potassium oxide), SO3 (Sulphur trioxide), P2O5 (phosphorus pentoxide) SiO2 (silicon dioxide) are acidic oxides.
CO2 + 2NaOH тЖТ Na2CO3 + H2O
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Alloying
It is method of improving the properties of a metal. If iron is mixed with a small amount of carbon (about 0.05%) it became hard and strong. When iron is mixed with nickel and chromium, we obtain stainless steel which is hard and does not rust. An alloy is a mixture of two or more metals or a metal and a non-metal. It is prepared by first melting the primary metal and then dissolving the other element in a definite proportion. It is then cooled at room temperature.
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Explain The Process Of Hydraulic Washing?
It is process in which crushed (powdered) ore is washed with stream of water. The light gangue particle is washed away in a stream of water whereas heavy mineral particle is settle down at the bottom. It is based on difference in density of an ore and impurities.
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What Do You Understand By The Froth Floatation Process?
This process is used to concentrate some ores especially Sulphide ores. In this process the finely powdered ores is mixed with water and a suitable oil like pine oil, in a large tank. It is based on the principal that the mineral particle is more wetted by oil, whereas the gangue particle is more wetted by water. Compressed air is bubbled through the mixture. As a result of agitation oil froth is formed which contain mineral which float on the top of water and can be separated easily. Impurities are left behind at the bottom.
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What Is Meant By The Magnetic Separation?
It is a process in which a magnetic ore is separated from non-magnetic impurities with the help of electromagnet. The ore is crushed and electromagnet are brought near it which attract the mineral particle leaving behind the gangue particle. Magnetite (iron ore Fe3O4) pyrolusite (magnesium ore MnO2), chromite (chromium ore Cr2O3) are enriched by magnetic separation.
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What Are The Properties Of Alloys?
Alloy of a metal with mercury is known as amalgam. It has been observed that melting point and electrical conductivity of an alloy are lower than those of the constituent metals. For example, brass which is an alloy of copper and zinc and bronze which is an alloy of copper and tin are not as good conductor of electricity as copper. Solder which is an alloy of lead and tin has a low melting point and it is used for welding electrical wires.
Roasting And Calcination
Roasting: The Sulphide ore is converted into oxide are by heating strongly in the presence of excess air. This process is known as roasting.
For example:
2ZnS + 3O2 тЖТ 2ZnO + 2SO2
Calcination: The carbonate ore is changed into oxide by heating strongly in limited supply of air. This is known as calcination.
For example:
ZnCo3 тЖТ ZnO + CO2
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