POINTS TO REMEMER-Class 10 – Science -Chemistry -Chapter 3 – Metals and Non-metals a

POINTS TO REMEMER-Class 10 – Science -Chemistry -Chapter 3 – Metals and Non-metals  

POINTS TO REMEMER  

➢ 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.