Railways Chemistry Some Important Man-Made Materials Some Important Man made Materials

Introduction

Chemistry has helped significantly in meeting human needs by providing chemical fertilizers, improved varieties of insecticides and pesticides to increase the yield of crops and fruits. It has given us a large number of lifesaving drugs. Also chemical industries manufacturing polymers, soaps, detergents, glass, ceramics etc.

Industrially Important Compounds Glass

It consists of a mixture of two or more silicates.

• Preparation of glass:
• Common glass (or soft glass): It is used to make bottles, glass wares etc. and is obtained by heating together silica (in the form of sand), sodium carbonate or sodium sulphate and chalk or lime stone (calcium carbonate). Some broken glass and a little coke are usually added. The glass so prepared consists of silicates of sodium and calcium.

\[N{{a}_{2}}C{{O}_{3}}(s)+\underset{\left( silica \right)}{\mathop{Si{{O}_{2}}(s)}}\,\to N{{a}_{2}}Si{{O}_{3}}(s)+C{{O}_{2}}(g)\]

\[N{{a}_{2}}S{{O}_{4}}(s)+Si{{O}_{2}}(s)\to N{{a}_{2}}Si{{O}_{3}}(s)+S{{O}_{3}}(g)\]

\[CaC{{O}_{3}}(s)+Si{{O}_{2}}(s)\to CaSi{{O}_{3}}(s)+C{{O}_{2}}(g)\]

• Hard glass: For preparation of hard glass \[{{K}_{2}}C{{O}_{3}}\] is used in place of\[N{{a}_{2}}C{{O}_{3}}\]. It consists of a mixture of calcium and potassium silicates.
• Physical properties of glass: Hard, rigid, high viscosity, bad conductor of heat and electricity, brittle, etc.
• Blowing: It is a method to cast the molten glass into different moulds. There are two different methods of glass blowing (i) Free blowing and (ii) Mould blowing
• Free blowing: It involves the blowing of air to inflate the molten glass which is gathered at one end of the blow pipe to give the desired shape.
• Mould blowing: This method was developed after' the technique of free blowing. In this method, molten glass is inflated into a wooden or metal carved mould with the help of blow pipe which gives the molten glass the shape and design of the interior of the mould.
• Chemical properties of glass

(i) It is resistant to action of air and acids except hydroflouric acid.

(ii) It is alkaline in nature.

(iii) It slowly reacts with water to form alkaline solution.

• Types of Glass

(i) Silica glass: For this type of glass the raw material used is 100% pure form of quartz. It is quite expensive. It is used in the manufacture of laboratory apparatus. It has low thermal expansion. Its softening point is very high and it is resistant to a wide variety of chemicals.

(ii) Alkali silicate glass: For it the raw materials used are sand and soda. It is also called water glass because it is soluble in water and used only as a solution. It is generally used to make gums and adhesives.

(iii) Lead glass: For this type of glass lead oxide is added to ordinary glass. The addition of lead oxide increases the density and also the refractive index. This type of glass is used for the manufacture of ornamental glass ware, decorative articles etc.

(iv) Optical glass: This type of glass is used in the manufacture of optical instruments like binoculars, spectacles, lenses, prisons, telescopes, microscopes etc. It is transparent and can be grounded into the required shape. It generally contains phosphorus, and lead silicates with little cerium oxide which absorbs UV radiations.

(v) Processed glass: The properties and applications of glass also depend upon the processing of glass. Some types of processed glass and their applications are given here:

(vi) Borosilicate glass: It contains silica and Boron oxide and small amount of oxides of sodium and aluminium. It is resistant to a wide variety of chemicals due to this property it is used in the manufacture of laboratory ware.

Fertilizers

• Fertilizers

Fertilizers are chemical compounds which when added to the soil increase their fertility and directly supply the need of essential elements [N, P, K] of primary importance.

Some Important Man Made Materials

• Classification: Chemical fertilizers are broadly classified into the following three types:

(i) Nitrogenous fertilizers: Ammonium sulphate, urea etc.

(ii) Phosphatic fertilizers: Super phosphate, ammonium phosphate

(iii) Potash fertilizers: Potassium chloride, potassium sulphate.

Soaps and detergents

• Soap: Fatty acid salts of sodium and potassium are known as soaps. These are prepared by the action of fatty acids with sodium hydroxide or potassium hydroxide.

Fatty acid + sodium hydroxide \[\to \] Soap + glycerol.

• Detergents are sodium salt of long chain sulphonic acids or alkyl hydrogen sulphate.
• Advantages of detergents over soaps

(i)  Detergents can be used for laundering even with hard water as they are soluble even in hard water.

(ii) Detergents possess better cleansing properties than soaps.

• Disadvantages of detergents over soap: Detergents are prepared from hydrocarbons, while soaps are prepared from edible fatty oils. Thus they are non-biodegradable.
• Saponification: It is the process of making of soap by the hydrolysis of fats and oils with alkalis. Both soaps and detergents are soluble in water and act as surfactants which reduce the surface tension of water to a great extent. This increases the water – fabric interaction as a consequence of which dirt particles, grease spots etc are washed away effectively. In other words soaps and detergents enhance the cleansing action of water.

Portland cement

• Portland cement: It was first discovered in England. It is essentially a mixture of lime stone and clay. It was called Portland cement because in presence of water it sets to a hard stone-like mass resembling with the famous Portland rock. The approximate composition of Portland cement is

Calcium oxide (CaO)       62%

Silica \[(Si{{O}_{2}})\]              22%

Alumina \[(Si{{O}_{2}})\]          7.5%

Magnesia \[(MgO)\]         2.5%

Ferric oxide \[(F{{e}_{2}}{{O}_{3}})\]   2.5%

The above compounds are provided by the two raw materials, namely lime stone (which provides CaO) and clay (which provides\[Si{{O}_{2}}\], \[A{{l}_{2}}{{O}_{3}}\] and \[F{{e}_{2}}{{O}_{3}}\]. In cement, almost entire amount of lime in present in the combined state as calcium silicate (2CaO. \[Si{{O}_{2}}\] and 3CaO. \[Si{{O}_{2}}\]) and calcium aluminates (3CaO. \[A{{l}_{2}}{{O}_{3}}\] and 4 CaO. \[A{{l}_{2}}{{O}_{3}}\]).

(i) Cement containing excess amount of lime cracks during setting; while cement containing less amount of lime is weak in strength.

(ii) Cement with excess of silica is slow-setting and that having an excess of alumina is quick-setting.

(iii) Cement containing no iron is white but hard to bum. Cement is manufactured by two processes, viz. wet and dry. A small amount (2-3%) of gypsum is added to slow down the setting of the cement so that it gets sufficiently hardened. Setting of cement is an exothermic process and involves hydration of calcium aluminates and calcium silicates.

• Important Biomolecules

Vitamins