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Concepts: Metals and Non-metals
Metals: Those elements which have good tendency to lose electrons (or electropositive in nature) are called metals. In their physical properties they are lustre, malleable, ductile and good conductors of heat and electricity.
Non-Metals: Non-Metals are those elements which have tendency to gain electrons to form anions. Thus non-metals are called electronegative in nature. They are generally soft and bad conductors of electricity.
Semi-Metals or Metalloids: Semi-metals or metalloids are those elements which behave like both metals and non-metals.
Following table shows the position of Metals, Non-metals and the metalloids in the modern periodic table.
Malleability: It is the property of metals by which metals can be converted into thin sheets by using a hammer.
Ductility: It is the property of metals by which metals can be drawn into thin wires.
Minerals: The naturally occurring compounds of elements are known as minerals.
Ores: The mineral from which element can be extracted easily and profitably is called an ore.
Gangue: The impurities present in the ore such as sand, rocks etc are known as gangue.
Calcination: It is the process of heating concentrated ore in the absence of air below its meting point.
Metallurgy: It is the process in which pure metals are extracted from their ores.
Concentration of ores: It is the process in which the unwanted impurities (gangue) are removed from the ores.
Alloy: Alloy is the homogeneous mixture of two or more metals or metal and non-metal.
Amalgam: Those alloys in which one of the metals is mercury.
Aqua regia: Aqua regia is Latin word which means â€˜Royal Waterâ€™. It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It is capable of dissolving metals like Gold and Platinum.
Galvanisation: It is a method by which iron and steel can be prevented from rusting. In this method a thin layer of Zinc is made on the article which prevents them from rusting.
Amphoteric oxides: Oxides of metals which have both acidic as well as basic behaviour are known as amphoteric oxides. Such metallic oxides react with acids as well as base to produce salt and water. Examples of Amphoteric oxides are aluminium oxide and zinc oxide.
Reactivity Series or activity series of metals: The series of metals in which they are arranged in order of their reactivity.
Electrolytic refining: It is the process of refining of metal in which impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of metal salt is used as an electrolyte. The apparatus is shown in the figure given below. When electric current is passed through the electrolyte, the impure metal from the anode is dissolved in the electrolyte and an equal amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution whereas the insoluble impurities settle down at the bottom of the anode which is known as anode mud. Following diagram shows the electrolytic refining of copper in which anode is impure copper and cathode is thin strip of pure copper while the electrolyte used is the copper sulphate solution.
Extraction of metals: The process of obtaining pure metal from its ores involves a series of steps which together known as extraction of metals. On the basis of their reactivity series metals can be grouped into three categories.
(i) Metals of low reactivity
(ii) Metals of medium reactivity
(iii) Metals of high reactivity.
There are separate steps for these groups for obtaining pure metals. As shown in following diagram.
Reaction of metals with oxygen: Generally all metals combine with oxygen to form metal oxide if we supply some heat.
Reaction of metals with water: Most of the metals react with water to form metal hydroxide and release hydrogen gas. For example just see the following chemical equation.
Reaction of metals with Acids: When metals react with acids they generally displace hydrogen from dilute acids.
Difference between Metals and Non-metals on the basis of their physical properties:
1. Metals are generally solid at room temperature. (Except Mercury)
1. Non-metals exist in all the three states i.e solid liquid and gas.
2. Metals are generally hard. (except sodium which can be cut using a knife)
2. Non-metals are generally soft. (except diamond which us the hardest substance on the earth)
3. Metals are Malleable; means can be converted into thinsheets using a hammer. (except sodium and potassium)
3. Non-metals are generally brittle. Will broke down intopieces when beaten by a hammer.
4. Metals are ductile, means they can be converted into thinwires.
4. Non-metals are non ductile.
5. Metals have shiny surface or they are lustrous.
5. They are non lustrous. (except iodine)
6. Metals can lose electrons so they are electropositive innature.
6. Non-metals gain electrons so they are electronegative innature.
7. Metals are good conductors of heat and electricity.
7. Non-metals are bed conductors of heat and electricity.(Except graphite)
8. Metals are sonorous. They produce a sound on striking witha hard surface.
8. They does not do so they are not sonorous.
9. Metals generally have high densities. (except alkalimetals)
9. Non-metals generally have low densities.
Some common, simple and Polyatomic Ions: Must learn to make chemical formula of a compound.
In text Questions page number 40
Question 1. Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
Question 2. Explain the meanings of malleable and ductile.
Malleable: A substance which can be beaten to convert into sheets are said to be malleable. Generally all metals are malleable. For example copper, iron etc.
Ductile: A substance which can be drawn into wires are said to be ductile. Generally all metals are ductile. For example silver, gold etc.
In text Questions page number 46
Question 1. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is high reactive element. If it is kept in open it can explosively react with oxygen to catch fire. Hence to prevent accidental damage sodium is immersed in kerosene oil.
Question 2. Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water
Question 3. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
(i)Which is the most reactive metal?
Answer: B is most reactive metal.
(ii) What would you observe if B is added to a solution of Copper (II) sulphate?
Answer: B will displace copper from copper sulphate.
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer: Arrangement of metals in the order of decreasing reactivity B>A>C>D
Question 4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute sulphuric acid.
Answer: Hydrogen gas is evolved when hydrochloric acid is added to a reactive metal. The chemical reaction when iron reacts with dilute sulphuric acid is
Question 5. What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Answer: When zinc is added to iron (II) sulphate then it will displace the iron from iron sulphate solution as shown in the following chemical reaction
In text Questions page number 49
Question 1.(i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?
In text Questions page number 53
Question 1. Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
Mineral: The naturally occurring compounds of elements are known as Mineral.
Ore: The mineral from which element can be extracted easily and profitably is called an ore.
Gangue: The impurities present in the ore such as sand, rocks etc are non as gangue.
Question 2. Name two metals which are found in nature in the free state.
Answer: Gold and Platinum
Question 3. What chemical process is used for obtaining a metal from its oxide?
Answer: A metal can be extracted from its oxide by the process of reduction
In text Questions page number 55
Quesiton 1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.
In which cases will you find displacement reactions taking place?
Answer: On the basis of reactivity series of metals the displacement reaction will take place as follows
Question 2. Which metals do not corrode easily?
Answer: Metals which have law reactivity such as silver, gold does not corrode easily.
Question 3. What are alloys?
Answer: An alloy is the homogeneous mixture of two or more metals or metals and non metals. For example brass is an alloy of copper and zinc.
Question 1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
Answer: (d) Since copper is more reactive than silver so it will displace silver from silver nitrate.
Question 2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.
Answer: (c) Applying a coating of Zinc.
Question 3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
Answer: (a) calcium reacts with oxygen to give calcium oxide which is dissolved in water to give lime water.
Question 4. Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.
Answer: (c) Zinc is more reactive then tin. Which may react with food items and make it unfit for health.
Question 5. You are given a hammer, a battery, a bulb, wires and a switch
(a) How could you use them to distinguish between samples of metals and Non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Answer: (a) If the substance can be hammered to convert into sheets then it is metal if it is broken into pieces then it is non-metal. Set up the arrangement using bulb, battery, wire and switch as shown in figure. Place the substance between Point A and B if the bulb starts glowing then the substance is a Metal otherwise it is non-metal because metals are good conductor of electricity.
(b) Generally above methods can be used to identify metals and non-metals. But there are some exceptions also for example Sodium is metal which is not malleable in fact it is brittle. Graphite allotrope of non-metal carbon is a good conductor of electricity.
Question 6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: Oxides of metals which have both acidic as well as basic behaviour are known as amphoteric oxides. Such metallic oxides react with acids as well as base to produce salt and water. Examples of Amphoteric oxides are aluminium oxide and zinc oxide.
Question 7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer: Iron and aluminium will displace hydrogen from dilute acids as they more reactive then hydrogen. Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.
Quesiton 8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer: During electrolytic refining, impure metal is made anode and a thin strip of pure metal M is made cathode and the electrolyte used is the soluble salt of Metal M which is to be refined.
Question 9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.
(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical
equation for the reaction taking place.
(i)No Change in colour of litmus paper.
(ii) The colour of litmus paper will turn red because sulphur is a non-metal and the oxides of non-metal are acidic in nature.
Quesiton 10. State two ways to prevent the rusting of iron.
Answer: (1) by Painting or galvanising, (2) By making alloys
Quesiton 11. What type of oxides are formed when non-metals combine with oxygen?
Answer: When non-metals are combined with oxygen then neutral or acidic oxides are formed. Examples of acidic oxides are NO2, SO2 and examples of neutral oxides are NO, CO etc.
Quesiton 12. Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
(a) Platinum, gold and silver are used to make jewellery because these are low reactive metals so rarely corrosion occur (In silver) and hence do not lost their shine and lustre.
(b)The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.
(c)This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al2O3 ) is formed which prevent further corrosion.
(d)Carbonate and sulphide ores are usually converted into oxides during the process of extraction because it is easier to obtain metal from its oxide as compared with its sulphides or carbonates ore.
Quesiton 13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer: In tarnished copper vessel there is layer formed due to corrosion which is basic in nature which is dissolved in the lemon or tamarind juice which are acidic in nature. Thus the vessel get thoroughly cleaned.
Question 14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer: Differences between metals and non-metals on the basis of their chemical properties.
1. Oxides of metal are basic in nature.
1. Oxides of non-metals are acidic innature.
2. Metals displace hydrogen from diluteacids.
2. They cannot do so.
3. Metals form chlorides which areelectrovalent or ionic compounds.
3. Non-metals form chlorides which arecovalent compounds.
4. they displace hydrogen from water
4. They cannot do so.
Question 15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer: The solution he had used was Aqua regia. Aqua regia is Latin word which means â€˜Royal Waterâ€™. It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It is capable of dissolving metals like Gold and Platinum. Since the outer layer of the gold bangles is dissolved in aqua regia so their weight was reduced drastically.
Quesiton 16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer: Copper is used to make hot water tanks and not steel this is because the iron (in steel) is more reactive than then copper also it react with hot steam to produce ferrosoferric oxide. Due to which the body of tank will become weaker and weaker. While copper does not react with hot water.
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