Ores An ore is a naturally occurring mineral from which one or more metal can be profitably extracted.

Transcription

1 Metals & Non Metals INTRODUCTION All the elements can be classified as metals or non-metals depending on their properties. If we call one element as metal then it will show some definite set of properties and if we call it non-metal then it will show some other definite set of properties. So, first we will discuss general characteristics of metals and non metals so that we can distinguish them easily and then we will discuss some of their physical properties and chemical properties in detail along with their uses. CHARACTERISTICS OF METALS AND NON METALS Out of the 92 naturally occurring elements, about 70 are identified as metal and about 22 as non-metals. Copper, iron, zinc, aluminium, gold, silver, tungsten displays the properties of metals. Like they produce ringing sound when struck on hard surfaces. They are good conductors of heat and electricity. Chlorine, bromine, helium, oxygen, carbon are known as non-metals. Bromine is liquid while iodine is a soft solid at room temperature. They melt at low temperature, break easily when hammered and are bad conductors of heat and electricity. Non metals normally display properties opposite to that of metals. Exercise 1: Fill in the blanks (i) Metals produce..sound when struck to hard surface. (ii) Non-metals are conductors of heat. (iii) Iron is example of..and chlorine is of OCCURRENCE Non-metals are found in free state as well as in the form of compounds. Helium, neon, krypton and xenon are known as noble gases, occur in elemental form in air. Nitrogen and oxygen can be found in air in elemental form as well as in compound form. But in general, one can say that most of them occur in compound form. Non-metals can also be obtained from various sources like mines. For example nitrogen and oxygen gases are obtained by fractional distillation of liquefied air. Metals are normally very reactive in nature, so it is tough to find them in free state in nature. Normally metals are found in the form of their oxides and sulphides. Very few metals like gold, silver and copper can be excepted to occur in free state in nature. Metals like manganese, aluminium and iron occur as oxides and copper, zinc, nickel, antimony and cadmium occur in the form of sulphides. Silicate minerals are also another form which is available in abundance. Many technologies has been developed to get metal from their ores. Different ores are required to get different metal and for all this we also require different technologies to extract metal from their respective ores. Ores An ore is a naturally occurring mineral from which one or more metal can be profitably extracted. Gangue/Matrix Impurities present in the ore are known as gangue or matrix. Metallurgy Metallurgy is the science of extracting metal from their ores and purifying them.

2 PDT Courseware (FTRE)-8 th moving to 9 th -CH-2 Metallurgy involves three main processes. (a) Concentration of ore (b) Reduction (c) Refining of metal Concentration of Ore In this stage the impurities are removed and the concentration level of ore is increased. This mainly involves the physical processes. (i) Gravity separation or hydraulic washing. (ii) Froth-floatation method (iii) Magnetic separation Reduction The compounds of metals like metal oxides are reduced to get free metal. Refining of Metal It is done to get 100% pure metal. For example by electrolytic refining. Illustration 1: Define the term ore. Solution: An ore is a naturally occurring mineral from which one or more metal can be profitably extracted. Exercise 2: Name the metals and non-metals which occur in free state? PHYSICAL PROPERTIES OF METALS AND NON METALS All the metals and non-metals have some of their characteristics properties. Physical State Metals have a definite shape in normal conditions. Metals are solids at room temperature and have high melting points. Mercury is the only exception as this is the only metal which exists as liquid at room temperature. Non-metals can be solids, liquids or gas at room temperature. Sulphur is gas at room temperature. The boiling point and melting point of non-metals are less as compared to metals. Majority of non-metals are gases at room temperature. Lusture Metals are very shiny and have metallic Lusture, which make them useful for jewellery purpose. On the other hand non-metals have wide variety of colour range but have very dull Lusture. Malleability The property of beating a metal into thin sheets is called malleability. Non-metals are not malleable. Ductility Ductility is the property that allows the substance to be drawn into wires. Metals have this property. This is the reason why we are able to see the wires of copper, aluminium and iron. Non-metals are not ductile in nature. We can not get wires from non-metals.

3 PDT Courseware (FTRE)-8 th moving to 9 th -CH-3 Conductivity Metals are good conductors of heat and electricity. Gold is best conductor followed by silver, copper and aluminum. Many of non-metals are insulators and in general they are supposed to be bad conductors of electricity. Hardness It is difficult to cut metal and they are also able to bear a heavy load over them. Metals are hard substances. On the other hand, non-metals are brittle. Although sodium and potassium are so soft that they can be cut with knife while diamond is hardest substance (a form of carbon). So In general we can say that an element can be easily identified as being metal or non-metal by comparing its properties with the general properties of metals and non-metals. But some times some elements do not fall in any categories then these are known as semi metals or metalloids. Example Silicon, germanium Exercise 3: Name, whether this property is shown by metal or non-metal. (a) Hardness (b) Bad conductance of heat (c) Ductility (d) Malleability (e) Lusture CHEMICAL PROPERTIES OF METALS AND NON METALS Metals and non-metals show different behaviour toward different chemicals. Reaction with Oxygen In general, metals form oxides on combining with oxygen. Water solutions of these oxides are alkaline or basic in nature. For example: 2Mg O2 2MgO ; Mg H O Mg OH 2 2 This Mg(OH) 2 solution changes red litmus into blue indicating that the solution is alkaline. Similarly, non-metals on reaction with oxygen forms their oxides but on adding small amount of water to these oxides, solution becomes acidic. For example: S O SO 2 2 SO2 H2O H2SO3 The solution of H 2 SO 3, changes blue litmus paper into red. This change indicates that the solution is acidic in nature. So for differentiating metals from non-metals we can say that oxides of metals are basic in nature and oxides of non-metals are acidic in nature. Reaction with Water Different metals react with water at different rates. Sodium reacts violently with water to form sodium hydroxide and hydrogen gas is librated in the process. 2Na H O 2NaOH H g 2 2 Magnesium reacts mildly with cold water but vigorously with hot water. Mg 2H O Mg OH H g Similarly zinc and iron react very mildly with steam whereas copper, silver and nickel do not react with water. Non-metals do not react with water. Some of the non-metals like phosphorous is kept in water. So that its contact from air can be avoided.

4 PDT Courseware (FTRE)-8 th moving to 9 th -CH-4 Reaction with Acids Aluminium, iron and copper when react with dilute hydrochloric acid, aluminium and iron forms AlCl 3 and FeCl 2 and H 2 gas is evolved in each case but copper does not react. 2Al 6HCl 2AlCl3 3H2 Fe HCl FeCl2 H2 Normally non-meals do not react with acids although sulphur, reacts with hot concentrated nitric acid. S 4HNO SO 4NO 2H O Illustration 2: Write the balance chemical reaction for the following: Burning of sulphur. Solution: S O2 SO2 Exercise 4: Write the reaction between sulphur and hot conc. nitric acid. Metal Replaces Metal A metal can replace another metal in the same way as metal replaces hydrogen from acid. These are same as displacement reactions. Normally more reactive metals displace the less reactive metals like Mg replaces copper from CuSO 4. The decreasing order of reactivity of metals are: Potassium > Sodium > magnesium > aluminium > Zinc > Iron > Lead > Copper > Silver > gold This sequence is also known as activity series. More reactive metals are hard to be found out in free form. They have tendency to form compound. Potassium is therefore kept in kerosene. Fe CuSO FeSO Cu 4 4 Mg CuSO4 MgSO4 Cu Zn CuSO4 ZnSO4 Cu Noble Metals Metals which have very less tendency to react and can be found in free state in nature like gold, silver and platinum are known as noble metals. They have the property to maintain their metallic Lusture for a long time. Gold remains unaffected by air, water and also acidic and basic substances. Gold is soft, extremely ductile and malleable. It dissolves in aqua regia. (A mixture of conc. HNO 3 acid HCl in the ratio 1:3 by volume) Exercise 5: State True and False: (a) Iron is a noble metal. (b) Gold content is expressed in terms of carat. (c) Gold is very less ductile. USES OF COMMON METALS AND NON METALS Metals are strong, rigid and hard, these properties of metals can be used for making heavy machinery (like automobiles, aeroplanes, trains, trucks etc). Iron is most commonly used metal. It is used for making small objects like pin and in giant structures. Aluminium is another widely used metal due to its small density It is useful for making aeroplanes.

5 PDT Courseware (FTRE)-8 th moving to 9 th -CH-5 Ability to conduct heat and electricity make metals very useful. Metals like copper, iron and aluminium is used for these purposes. Aluminium wires are widely used. Gold and silver is used for making jewellery. Good reflecting property of silver is used for making mirrors. Silver foils are widely used for wrapping of food items, medicines and other materials. Sodium is a constituent of common salt, main constituent of cement is calcium oxide and aluminium oxide. Oxygen, a non-metal is essential for life. Oxygen is also a constituent of water. Oxygen also support combustion reaction while nitrogen provides nutrition to plants. Chlorine is used for killing the germs. Sulphur is major constituents of important industrial chemical. Tincture of iodine is used as an antiseptic. Illustration 3: What is the use of sulphur? Solution: It is a major constituent of important industrial chemical. Illustration 4: What is the use of nitrogen for plants? Solution: It provides nutrition to plant. Exercise 6: (i) Write the uses of gold. (ii) Write the uses of iron.

6 PDT Courseware (FTRE)-8 th moving to 9 th -CH-6 ANSWERS TO EXERCISE Exercise1: Exercise 2: Exercise 3: (i) Ringing (ii) bad (iii) metal, non-metal Gold, silver (metals), helium, neon, krypton, xenon (non metal) (a) Metal (b) non metal (c) metal (d) metal (e) Metal Exercise 4: S 4HNO3 SO2 4NO2 2H2O Exercise 5: Exercise 6: (a) False (b) True (c) False (i) For making jewellery (ii) For electricity purpose

7 PDT Courseware (FTRE)-8 th moving to 9 th -CH-7 SOLVED PROBLEMS SUBJECTIVE 1. What happen when? (c) Sodium is placed on water. (d) Zinc granules are kept in copper sulphate solution. (e) Sulphur dioxide is dissolved in water. (c) 2Na 2H2O 2NaOH H2 (d) Zn CuSO4 ZnSO4 Cu (e) SO2 H2O H2SO3 2. A set of metals in order of their increasing chemical reactivity is given below: Silver, copper, hydrogen, lead, iron, zinc, magnesium and sodium (a) Which of above metals is stored in kerosene? (b) Which metal will react with cold water? (c) Which gas will liberated when metals reacts with cold water? (d) Which of the metals will react with oxygen when heated? (e) Which of metals become black in presence of hydrogen sulphide? (a) Sodium (b) Sodium (c) Hydrogen (d) Zinc, magnesium (e) Silver 3. List the different uses of metals that you come across in everyday life. Metals used for (a) machinery (b) automobiles, Aeroplanes, trains etc (c) cooking, utensils, electrical gadgets. (d) electrical wires (e) thin sheets 4. Give two uses of zinc. (a) It is used in galvanizing iron. (b) Making container of dry cells.

8 PDT Courseware (FTRE)-8 th moving to 9 th -CH-8 OBJECTIVE MULTIPLE CHOICE QUESTIONS (SINGLE OPTION CORRECT) 1. Phosphorous is kept in water to protect it from (A) nitrogen (B) oxygen (C) hydrogen (B). Oxygen being more reactive than phosphorous has the tendency to oxidize it. So to prevent it is kept in water. 2. Metals shows (A) malleability (C) conductance (B) ductility (D) all of them (D). Malleability, ductility and conductivity are the characteristic property of metals. 3. Highest level of conductivity is expected by (A) gold (C) Aluminium (B) silver (A). Gold is known to be the best conductor of heat and electricity among silver and aluminium. 4. The property which is used in making of wires from metals (A) malleability (B) ductility (C) conductance (A). Ductility is the characteristic property of metals which tells the ability of the metals to be drawn into wires. 5. Highest melting point is expected by (A) metals (C) metalloids (B) non-metals (D) non of these (A). The intermolecular force of attraction is higher in comparison to metalloids and non-metal. As a result, more energy is required to break the bonds. Hence, metals posses higher melting point. 6. Metal oxides are (A) acidic (C) neutral (B) basic (B). Metals oxides and hydroxides have the tendency to produce hydroxyl ion in aqueous solution, hence basic in nature. 7. Oxides of non-metals are (A) acidic (C) neutral (B) basic (A). Oxides of non-metals are generally acidic in nature as they are deficient in electrons and whenever these oxides comes in contact with an electron rich species, starts acting as a very good Lewis acid. 8. Which of the following do not react readily with water? (A) zinc (B) sodium (C) potassium (D) copper

9 PDT Courseware (FTRE)-8 th moving to 9 th -CH-9 (D). The reactivity of copper is less than hydrogen, so it does not react with water to replace hydrogen from it. 9. The gas liberated when water react with metal (A) nitrogen (B) oxygen (C) hydrogen (C). Whenever a metal reacts with water, an hydroxide is formed with the liberation of hydrogen gas. FILL IN THE BLANKS 10. are the good conductors of heat and electricity. Metals 11. Examples of metals are.and sodium, iron 12..display Lusture. metals TRUE OR FALSE 13. Sodium is more reactive than magnesium. True 14. Metals are used for making the body of automobiles, Aeroplanes, trains etc. True

10 PDT Courseware (FTRE)-8 th moving to 9 th -CH-10 ASSIGNMENT SUBJECTIVE 1. Explain the term metallurgy. 2. Name the metal which occurs in free state. 3. Why tincture iodine used to protect wound from germs? 4. Compare the physical properties of non-metals and metals with respect to (a) malleability (b) ductility (c) conductivity 5. Taking example of magnesium and sulphur, explain how non metals produce oxides with different characteristics. 6. Which of the following will cause acidic oxide: P, H, Na, Ca. 7. Which metal is the poorest conductor of heat & electricity? 8. Give the reason why graphite is used as an electrode in dry cell? 9. Give different uses of metals in daily life 10. Which is the best conductor of electricity?

11 PDT Courseware (FTRE)-8 th moving to 9 th -CH-11 OBJECTIVE MULTIPLE CHOICE QUESTIONS (SINGLE OPTION CORRECT) 1. Which metal will replace copper from CuSO 4 solution? (A) Zn (B) Fe (C) Mg (D) All of them 2. Which metal is most reactive among the following? (A) potassium (B) gold (C) silver (D) iron 3. Which one of the following is not a noble metal? (A) gold (C) iron 4. Which is not the characteristic property of gold? (A) ductile (C) malleable (B) platinum (D) silver (B) highly reactive 5. Which of the following is not used for making ornament? (A) silver (B) gold (C) platinum (D) zinc FILL IN THE BLANKS 6. The number of metals are much.than non metals. 7. Examples of non-metals are.and. 8...metals are exist is free state. TRUE OR FALSE 9. Noble gases are found in free state 10. Non metals are generally brittle.

12 PDT Courseware (FTRE)-8 th moving to 9 th -CH-12 ANSWERS TO ASSIGNMENT SUBJECTIVE 1. Metallurgy is the science of extracting metal from their ores and purifying them. 2. Gold, silver 6. P 7. Lead 10. Silver OBJECTIVE MULTIPLE CHOICE QUESTIONS (SINGLE OPTION CORRECT) 1. D 2. A 3. C 4. B 5. D FILL IN THE BLANKS 6. More 7. Hydrogen & nitrogen 8. noble TRUE OR FALSE 9. True 10. True