Chemistry

♦ Metals are lustrous, malleable, ductile and have high density.
♦ Metals are generally good conductors of heat and electricity.
♦ Metals form positive ions by losing electrons.
♦ All metals combine with oxygen to form metal oxides.
♦ Metal oxides are basic in nature.
♦ Metals react with chlorine to form electrovalent chlorides of metals.
♦ Metals like Li, Na and Ca form hydrides with hydrogen.
♦ There are metal-bearing substances below the earth's surface which are called minerals.
♦ The minerals from which metals can be obtained profitably are called ores.
♦ A flux is a substance which is added to the furnace charge to remove nonfusible impurities present in the ore.
♦ Flux combines with the nonfusible impurity to convert it into a fusible substance known as slag.
♦ Nonmetals are generally bad conductors of heat and electricity.
♦ All nonmetals are electronegative.
♦ The function of limestone in the extraction of iron is to provide calcium oxide (CaO) for the formation of the slag CaSiO₃.
♦ Alloy steels are prepared by adding a small quantity of nickel, cobalt, chromium, tungsten, molybdenum, manganese or silicon to steel.
♦ The heating of steel to redness and then cooling it slowly is called tempering of steel.
♦ Rusting of iron is an oxidation reaction which occurs in the presence of air and water.
♦ Aluminium is the most abundant metal in the earth's crust.
♦ The process of extracting metals from their ores and refining them for use is called metallurgy.
♦ The unwanted materials present in an ore are called gangue.
♦ Froth floatation is a method used for the concentration of some ores.
♦ Calcination is the process of heating an ore strongly so that volatile impurities are removed.
♦ Roasting is the process of heating an ore in a controlled supply of air at a controlled temperature.
♦ Smelting is the process of obtaining metals from their compounds.
♦ Bauxite is an ore from which aluminium metal is commercially obtained.
♦ The most important are of aluminium is bauxite (Al₂O₃.2H₂O).
♦ Slow destruction of metals by the action of air, carbon dioxide, moisture, etc., is known as corrosion of metals.
♦ An alloy consists of two or more metals, or a metal and a nonmetal. Brass is an alloy of copper and zinc.
♦ The property of an element to exist in two or more ,... different forms is known as allotropy.
♦ The most important ore of copper is copper pyrite (CuFeS₂).
♦ Copper when heated in air at 300°C forms cupric oxide (CuO), while at 1000°C forms cuprous oxide (Cu₂O).
♦ Silver does not react with water and hydrochloric acid. It, however, reacts with nitric acid to produce NO₂ gas.
♦ Gold dissolves in aqua regia. Aqua regia is a mixture of conc. hydrochloric acid and conc. nitric acid in the volume ratio 3 : 1.
♦ Lead on rubbing leaves a mark on paper. Lead is the poorest conductor of heat.
♦ Zinc when heated with a concentrated solution of sodium hydroxide gives off hydrogen gas, while sodium zincate is left in solution.
♦ Sulphur is used in vulcanization of rubber.
♦ Metals are lustrous, malleable, ductile and have high density.
♦ Metals are generally good conductors of heat and electricity.
♦ Metals form positive ions by losing electrons.
♦ All metals combine with oxygen to form metal oxides.
♦ Metal oxides are basic in nature.
♦ Metals react with chlorine to form electrovalent chlorides of metals.
♦ Metals like Li, Na and Ca form hydrides with hydrogen.
♦ There are metal-bearing substances below the earth's surface which are called minerals.
♦ The minerals from which metals can be obtained profitably are called ores.
♦ A flux is a substance which is added to the furnace charge to remove nonfusible impurities present in the ore.
♦ Flux combines with the nonfusible impurity to convert it into a fusible substance known as slag.
♦ Nonmetals are generally bad conductors of heat and electricity.
♦ All nonmetals are electronegative.
♦ The function of limestone in the extraction of iron is to provide calcium oxide (CaO) for the formation of the slag CaSiO₃.
♦ Alloy steels are prepared by adding a small quantity of nickel, cobalt, chromium, tungsten, molybdenum, manganese or silicon to steel.
♦ The heating of steel to redness and then cooling it slowly is called tempering of steel.
♦ Rusting of iron is an oxidation reaction which occurs in the presence of air and water.
♦ Aluminium is the most abundant metal in the earth's crust.
♦ The process of extracting metals from their ores and refining them for use is called metallurgy.
♦ The unwanted materials present in an ore are called gangue.
♦ Froth floatation is a method used for the concentration of some ores.
♦ Calcination is the process of heating an ore strongly so that volatile impurities are removed.
♦ Roasting is the process of heating an ore in a controlled supply of air at a controlled temperature.
♦ Smelting is the process of obtaining metals from their compounds.
♦ Bauxite is an ore from which aluminium metal is commercially obtained.
♦ The most important are of aluminium is bauxite (Al₂O₃.2H₂O).
♦ Slow destruction of metals by the action of air, carbon dioxide, moisture, etc., is known as corrosion of metals.
♦ An alloy consists of two or more metals, or a metal and a nonmetal. Brass is an alloy of copper and zinc.
♦ The property of an element to exist in two or more ,... different forms is known as allotropy.
♦ The most important ore of copper is copper pyrite (CuFeS₂).
♦ Copper when heated in air at 300°C forms cupric oxide (CuO), while at 1000°C forms cuprous oxide (Cu₂O).
♦ Silver does not react with water and hydrochloric acid. It, however, reacts with nitric acid to produce NO₂ gas.
♦ Gold dissolves in aqua regia. Aqua regia is a mixture of conc. hydrochloric acid and conc. nitric acid in the volume ratio 3 : 1.
♦ Lead on rubbing leaves a mark on paper. Lead is the poorest conductor of heat.
♦ Zinc when heated with a concentrated solution of sodium hydroxide gives off hydrogen gas, while sodium zincate is left in solution.
♦ Sulphur is used in vulcanization of rubber.