Metals and Non-metals Assignment (Solved)

METALS & NON-METALS 1. What are pure substances? Give examples. The materials made up of the same kind of particles are known as pure substances. 2. Why elements differ from each other in their physical and chemical properties? The elements differ from each other in the physical and chemical properties as different elements consist of atoms of different kinds. 3. What is classification of elements and on what basis elements are classified? The elements showing similar properties are grouped together and their general characteristics are studied. This is known as classification of elements. They are classified on the basis of Physical and Chemical Properties as Metals and Non Metals. 4. Name few reactive and lesser reactive metals. Reactive – Potassium, Sodium. Less Reactive – Gold, Silver, Platinum. 5. Name two non-metals which exist in Free State as well as in combined state. Oxygen and Nitrogen exist in Free State as well as in combined state in the form of compounds like oxides and nitrates. 6. Write difference between mineral and ore. A mineral is a naturally occurring inorganic substance found deep under the earth whereas an ore is a mineral from which one or more metals can be extracted profitably. 7. What is metallurgy? Explain its steps. The sequence of processes used to extract a metal in its pure form from its ore is known as metallurgy. It generally involves the following steps  1) Concentration of Ore – The process of removal of impurities from ore. 2) Reduction – The process of reducing a metal ore to get the metal in its free state. 3) Refining of Metal – The metal obtained by reduction is impure. The process of purification of metals is known as refining. 8. Compare metals and non-metals on the basis of malleability, tensile strength and ductility. Malleability means “beating into sheets”. Metals are malleable. Nonmetals are not malleable (They are ductile). Ductility means “drawing into wires”. Metals are ductile. Non-metals are not. Tensile Strength is the property due to which a substance can bear a lot of strain without breaking. Metals have high tensile strength. Nonmetals have low tensile strength except carbon – fiber. 9. Name a non-metal which has a luster? Iodine 10. Why copper and iron are used for making cooking utensils and water boilers? Copper and Iron are good conductors of heat. They are good thermal conductors. It is due to this property that they are used for making utensils and water boilers. 11. Why copper wires are used for electrical fittings? Copper Wires are good conductors of electricity. It is due to this property that they are used in electrical fittings. 12. Why graphite is used in batteries? Most of the non-metals are bad conductors. But Graphite (A form of Carbon) is an exception. It is a good conductor and is used in batteries. 13. What are metalloids? Give few examples. Those elements which show the property of both metals and nonmetals are called metalloids. For eg. Silicon, Germanium, Arsenic. 14. Compare metals and non-metals on the basis of any three chemical properties.

1) Reaction with oxygen – Metals react with oxygen to form metal oxides which are basic in nature. Mg + O2  MgO Non-metals react with oxygen to form basic oxides which are acidic. C + O2  CO2 CO2 + H2O  H2CO3 2) Reaction with Water – Metals differ in their reactivity towards water. Sodium and potassium are highly reactive. Magnesium does not react with cold water but react on heating. Zinc reacts with boiling water and Iron reacts with steam. Copper, Silver, Gold, Platinum does not react with water at all. MgO + H2O  Mg(OH)2 + H2 Non-Metals do not react with water. 3) Reaction with Acids – Most metals react with dilute Hydrochloric Acid to liberate hydrogen gas and form metal salts. Some metals like Copper and lead do not react with HCl. They react with sulphuric acid and nitric acid but do not liberate hydrogen gas. Metals like Gold and Platinum do not react with acids. Non-Metals generally do not react with acids. But Sulphur and Phosphorus react with hot, concentrated Sulphuric Acid and nitric acid. 15. A metal is ignited and it burns with a bright white light and forms a white powder. The powder dissolves in water forming an alkaline solution. Identify the metal. Write the two chemical reactions involved. The metal is Magnesium. The reactions involved are  Mg + O2  MgO MgO + H2O  Mg(OH)2 16. Write an activity to show that non- metals react with oxygen to form non-metallic oxides which are acidic in nature. Take a small piece of charcoal on a spoon and ignite it. Put the spoon is a jar and cover it with a lid. Remove the spoon after some time. Add water in the jar and cover it again. Mix the contents in the jar by shaking it. Now pour the solution in a watch glass and put a strip of blue litmus paper. The blue litmus paper turns red indicating that it is an acid. C + O2  CO2 CO2 + H2O  H2CO3 Thus non-metallic oxides are acidic in nature. 17. Compare the reactivity of the following metals on the basis of their reactivity towards water.  Zinc, Sodium, Iron, Potassium, Magnesium Sodium and potassium are highly reactive. Magnesium does not react with cold water but react on heating. Zinc reacts with boiling water and Iron reacts with steam. 18. Why phosphorous is kept in water? Phosphorus is kept in water to prevent its contact with air, as it catches fire on reaction with air. 19. Write balanced chemical equation for the following Magnesium reacts with warm water MgO + 2H2O  Mg(OH)2 + H2  Zinc granules are added to dilute sulphuric acid Zn + H2SO4  ZnSO4 +H2  Iron nails are dipped in dilute hydrochloric acid Fe + 2HCl  FeCl2 + H2  Magnesium ribbon is dipped in copper sulphate solution Mg + CuSO4  MgSO4 + Cu  Copper wire is dipped in silver nitrate solution Cu + AgNO3  CuNO3 + Ag 20. What is reactivity of metals and reactivity series?

The tendency of an element to react with other substances to form compounds is known as reactivity. The series of metals arranged in the order of their decreasing reactivity is called the reactivity series. 21. Name the most and least reactive metal? Most reactive  Potassium. Least Reactive  Platinum 22. What are displacement reactions? Explain with the help of an example. A reaction in which a more reactive metal displaces a lesser reactive metal from the aqueous solution of its salt is a displacement reaction. For example  Mg + CuSO4  MgSO4 + Cu 23. What are noble metals? Give examples. Metals which are least reactive are called noble metals. For eg. Gold and Platinum. 24. Why pure gold cannot be used for making jewellery? Pure Gold is very soft. Therefore, it cannot be used to make jewellery in this form. For this purpose, it is mixed with silver and copper to make it hard. 25. What is a carat? The purity of gold is expressed in carats or karats. A carat means the number of parts of gold present in 24 parts of the mixture of gold and other metals. 26. Give two uses of following metals Gold  It is used in making jewellery and electroplating other metals like copper and silver.  Platinum  It is used in making dentistry and in making scientific instruments. It is also used in making jewellery.  Iron  It is the most widely used metal. It is used in making cooking utensils, water boilers, stoves, toys, tools, pipes etc.  Aluminium  Being very light, it is used in making air craft bodies. It is also used in making cooking utensils and thin foils for packaging.  Copper  It is mostly used in making electrical cables and other electrical good. It is also used in making cooking utensils.  Silver  It is used for making jewellery, decorative pieces etc. It can also be converted into thin foil and used for decorating food stuffs. Gold and Silver wires are also used for high precision electrical contacts in computers. 27. What are alloys? Why are alloys made? An alloy is a homogenous mixture of two or more metals or a metal and a non-metal. Alloys are generally stronger and harder and are resistant to corrosion. 28. Write composition and uses of the following alloys Steel  Iron + Carbon. Construction material, machine parts.  Stainless steel  Iron + Nickel + Chromium. Making utensils, cutlery, and surgical implements.  Brass  Copper + Zinc. Making utensils, decorative statues, nuts and bolts.  Bronze  Copper + Tin. Making utensils, Coins, Medals and Statues.  German silver  Copper + Zinc + Nickel. Making table ware.  Duralumin  Aluminum + Copper + Magnesium + Manganese. Making air craft bodies and automobile parts.  Alnico  Aluminum + Nickel + Cobalt. Making magnets.  Gun-metal  Copper + Tin + Zinc. For making Gun-barrels. 29. Give one use of the following non-metal Nitrogen  In the form of fertilisers, they are essential for the growth of plants and seed.  Phosphorous  It is used in matchbox industry and in fertilisers.

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Iodine  Iodine is used as an antiseptic. Sulphur  It is used for making fire crackers, Gun powder and Sulphuric Acid. Oxygen  It is essential for all living beings. Carbon  a) Diamond – It is used in making jewellery and in cutting and grinding tools. b) Graphite – It is used in batteries and in pencils.