SOAPS AND DETERGENTS std 8 to 10 GSEB CBSE

Preparation of soap

SOAPS AND DETERGENTS

Soaps – preparation of soaps – 

Detergents – 

advantages and disadvantages.

REVIEW

You have learnt the reasons for hardness of water.

Let us recall some of them.

·       Water which readily produces lather with soap is called soft water and that which does not readily produce lather is called hard water.

·       Hard water contains dissolved sulphates, chlorides and bicarbonates of calcium and magnesium.

·       The natural water is generally impure.

·       The polar nature of water makes it an excellent solvent.

  INTRODUCTION

When water is used for washing, it dissolves dirt; but some dirt will not dissolve in water. Soaps and detergents help water to remove dirt. The rod detergent means something which cleans. Soapnut powder has been inuse for about 3,000 years. In India even now some still use soapnut powder as a natural soap to remove oily substance. People have been using soap for a long time.

 SOAPS

Metallic salts prepared from natural fats are called soaps. Soap is a sodium salt or potassium salt of long chain fatty acide that has clensing action in water. Sodium stearate, sodium oliate and sodium plamitate are some examples of soaps.

Stearic acid is a long chain fatty acid. Its formula is C₁₇H₃₅COOH. This reacts with sodium hydroxide to give a compound called sodium stearate, which has properties of soap.

Similarly, sodium hydroxide reacts with oleic acid and plamitic acid forming sodium oleate (C₁₇H₃₃COONa) and sodium palmitate C₁₇H₃₁ COONa) respectively.

Please note !

Fatty acids are organic compounds. The molecules of these compounds contain a carboxyl group (-COOH). These molecules react with a trihydric alcohol called glycerol to form a class of compounds called esters. Groundnut oil, coconut oil, palm oil, caster oil, ginegely oil, animal fat etc are all esters of fatty acids. Fats and fatty oils are called glyceryl esters or glycerides.

While writing the formulae of inorganic csalts. It is the convention to write cation first However cation js written at end in the case of organic salts. Consider the following examples

Sodium chloride -        NaCL

Sodium acetate   -        Ch₃COONa

PRPARATION OF SOAP

Experiment : Take  about 30 ml of a vegetable oil in a beaker. Add about 60 ml of 20% sodium hydroxide solution to it. Heat slowly until the mixture boils. After 5-10 mimutes of boiling, add about 5g of sodium chloride to separate soap from the solution. Cool the solution. Observe the creamy layer of soap floating on the solution.

When a mixture of a oil/fat and a strong solution of sodium hydroxide is boiled in an iron tank, a sodium salt of the fatty acid and glycerol ane formed. The sodium salt of the fatty acid thus formed is nothing but soap.

Preparation of soap Experiment.

Video  how to make soap by cold process in Laboratory

A Swedish chemist, Carl Wihelm Scheel, discovered accidentally the process of preparation of soap in 1783. He boiled olive oil with lead oxide and obtained a substance which was sweet to taste. This substance is now known as glycerine.

Oil/fat + Sodium hydroxide – soap + glycerol

Glycerol

Glycerol is a sweet viscous liquid soluble in water. It is a byproduct of saponification process. It is commonly called glycerine. Its formula is CH₂OH.CHOH.CH₂OH. It is used in the manufacture of explosives, plastics. And pharmaceuticals. It is also used to prevent freezing.

Soap thus formed is separated with the help of sodium chloride. Addition of sodium chloride reduces the solubility of soap considerable. Soap, being lighter, flots like a cream on the solution. It is separated from the solution, suitable chemicals of suitable colour and odour are added to it and cast into moulds. When soap cools and solidifies, it is cut into desired shapes and packed. Glycerol exists in dissolved state in the solution. It is separated by distillation.

How does soap clean ?

Soap cleans process

Soap dissolves in water. This is due to the contrasting properties of the ends of the soap molecules. A soap molecule has a long hydrocarbon end (Ex:CH₃(CH₂)₁₆) and  a short ionic end containing COONA₊. The non-ionic hydrocarbon end attaches to the dirt or grease to form structures called ‘micelles’.

1.    water 2. soap molecule 3. Dirt

In micelles soap molecules are arranged radially. The end attached to water pulls out the dirt from the fabric. This can be washed off with water.

DETERGENTS

The term detergent is derived from a Latin word which means surface active. Synthetic detergents are commonly known as detergents. Detergents are also called soapless soaps. Detergents do not from insoluble ‘scum’ with magnesium and calcium ions present in hard water. Therefore, detergents clean better than soap even in hard water.

Detergents are sodium salts of long chain benzene sulphonic acid or sodium salts of long chain alkyl hydrogen sulphate. A detergent molecule consists of a large hydrocarbon group that is non-ionic and a sulphonate (SO₃- Na⁺) or a sulphate (SO₄-Na⁺) group that is ionic. Sodium n-dodecyl benzene sulphonate and sodium dodecyl sulphate are two well-known detergents.

Let us now consider a method of making detergents. Long chain hydrocarbons obtained from petroleum are treated with concentrated sulphuric acid. The organic acids produced during this process are neutralized with sodium hydroxide. The sodium salt obtained is a detergent.

 ADVANTAGES OF DETERGENTS OVER SOAPS

Detergents have more advantages that soap. Therefore. Detergents are more widely used that soap. Let as now turn our focus towards the advantages of detergents.

·       Detergents cleanse well even in hard water. Soap is not so good for washing when water is hard.

·       Detergents are made from hydrocarbons obtained from petroleum. Soap is prepared from vegetable oil or animals, fat that are usually edible. Detergents are not bio-degradable. Soaps are biodegradable.

·       Detergents cleanse well evening acidic medium. Soap does not cleanse well in such a medium.

Detergents have their disadvantages.

·       Detergents are non bio-degradable. They pollute water and soil.

Points to remember :

·       Metallic salts prepared from natural fats are called soaps.

·       Sodium hydroxide, fatty acid and sodium chloride are the raw materials used in the preparation of soap.

·       Sodium oleate and sodium palmitate are example for soap.

·       Detergents are also called soapless soap.

·       Detergents cleanse well even in hard water.

·       Detergents cleanse well in acid medium.

·       Detergents pollute water and soil.

·       The process of preparing soap using sodium hydroxide or potassium hydroxide is called saponification.

CONSERVATION OF WATER for std 8 to 10 GSEB CBSE

Conservation of water

CONSERVATION OF WATER



Water appears to be abundant source.
This has led to abuse of water.
Although more than 75% of the surface of the earth is covered with water, the water that is fit and available for our consumption is very much less.
Therefore we need to conserve water.
The effort made by the society towards the rational use, prevention of pollution and recycling of water is called conservation of water.

Distribution or water on earth

About 97% of the surface water is in the oceans.
This water being saline is unfit for use.
A large part of the remaining 3% water is stocked in the form of ice in the polar regions.
Only less than 1% water is supporting the organisms.
The demand for water is continuously increasing.
Obviously there is acute shortage of water.
There are many reasons for this. Some of these are listed below.

Ever increasing population.
Unsatisfactory management of water.
Deforestation and soil erosion.
Inadequate storage facilities.
Pollution of water.
Growing crop-breeds that consume more water.
Overuse of ground water.
Wastage through leakage, absorption, and evaporation.
Lowering of the storage capacity of water bodies due to silt collection.
Wasteful habits of using water.

METHODS OF CONSERVING WATER
Only 10% of the rainwater is being utilized in India. This utility is poor when compared with that of other countries. We need to collect and store more and more of this water and learn to use it. This is described as rain water harvesting. If we fail in this, a severe water famine is inevitable. We can do many things to conserve water. Some of these are briefly listed here. Try to learn more about them.

Uses of water record 

Remember
Some human activities causes pollution of water available for our use. It is also due to the unabated addition of substances like city effluents. Industrial wastes, synthetic chemicals, detergents, pesticides, chemical fertilizers, radioactive waster etc., into our environment. The widespread pollution of water due to agriculture, industries and city effluents, is one of the problems causing greatest concern to human kind. 

Collection of roof water 

Collection and use of roof water.

Improved methods of farming/irrigation.
Development of crop-breeds that consume less water.
Preventing pollution of water.
Conserving and recharging ground water.
Conservation of soil.
Preventing deforestation.
Removing silt in water bodies periodically.
Recycling of water wherever possible.

Avoiding wastage of water.

Remember
Here is a challenge for you !
Make an estimate of the amount of roof water that can be collected from your house roof during rainy season. Prepare an action plan to do this and implement the same. You may take this as a science project.

Project Activity
Make a list of the habits that result in wastage of water.
Prepare charts and make slogans to create awareness about these wasteful habits and display them.

POINTS TO REMEMBER
Water is classified as soft water and hard water.

Water that gives lather with soap easily and readily is called soft water.

Water that does not give lather with soap easily and readily is called hard water.

Hardness is due to the dissolved salts like salts of bicarbonates, chlorides and sulphates of calcium and magnesium.

Based on the kind of negative ions present along with MG2+ and Ca2+ ions, hard water is classified into two types namely temporary hard water and permanent hard water.

The hardness caused by dissolved magnesium bicarbonate and calcium bicarbonate is temporary hardness. Where as the hardness caused by dissolved magnesium and calcium chlorides or magnesium and calcium sulphates is called permanent hardness.

Hard water usually contains dissolved bicarbonates. On boiling these bicarbonates dissociate to from insoluble carbonates which go on depositing on the inner walls of the boiler. This results in scaling.

Boiling is a method of removal of temporary hardness.

The condensation of water vapour produced on heating water is the principle involved in distillation.

Soda process removes both temporary hardness and permanent hardness of water.

Naturally occurring sodium aluminium silicate is called zeolite and artificially prepared sodium aluminium silicate is called permutit.

The principle involved in permutit process is to convert the dissolved salts of calcium and magnesium into insoluble calcium and magnesium permutits respectively.

Although more that 75% of the surface of the earth is covered with water, the water that is fit and available for our consumption is very much less, hence we need to conserve water.

There are many reasons for the acute shortage of water. Some of them are listed below. 

Ever increasing population.

Unsatisfactory management of water.

Pollution of water.

Overuse of ground water.

Deforestation and soil erosion.

Some methods of conserving water are

Collection and uses of roof water – Rain water harvesting.

Improved methods of forming/irrigation.

Conservation of soil.

Preventing deforestation.

Preventing pollution of water.

METHODS OF SOFTENING HARD WATER, std 8 to 10 CBSE

Methods of removal of temporary hardness.

Boiling : You already know that temporary hardness is causes due to dissolved bicarbonates of calcium and magnesium.
Boiling is a method of removal of temporary hardness.
When water is boiled, the bicarbonates that cause temporary hardness are converted into insoluble carbonates, leading to the removal of Ca++ and Mg++ from water.

Calcium and Magnesium carbonate reaction with water

The precipitates that are formed are removed by filtering.
Boiling is the easiest method of softening a small quantity of water.
Softening a large quantity of water by boiling is highly expensive.
The Process is also time consuming.
Temporary hardness is rare.
Boiling removes the bicarbonate component only.
Therefore, we need to consider other methods of softening.

Do if yourself
It the water you use at home is hard, can it be softened by boiling ? Boil and examine. 

Methods of removal of permanent hardness.

1. Distillation : 

Water obtained from any source. However hard it may be, can be softened by distillation. Distilled water is both soft and pure. The condensation of water vapours produced on heating is the principle involved in this process. This method removes both temporary and permanent hardness. 

Think it over
Why is the process purification of seawater through distillation not so feasible ?

2. Soda process : 

Both temporary hardness and permanent hardness of water can be removed by adding sodium carbonate.
This method is called Soda process.
Sodium carbonate reacts with salts that causes hardness to give their respective carbonates.
The following chemical equations clarify these reactions. 

Different Chemical  reacts with salt equation.

The insoluble carbonates present in the softened water are removed by filtration.
The water softened by this method.
However, contains salts such as sodium sulphate, sodium chloride and so on.
The presence of these salts does not pose serious problems.
These salts do not come in the way of formation of lather with soap.

3. Permutit process : 

Permutit is used in softening hard water.
Naturally occurring sodium aluminium silicate is called zeolite.
This compound can also be prepared artificially. Artificially prepared sodium aluminium silicate is called permutit.
Permutit is prepared by heating quartz, sand, china clay and sodium carbonate.
Fusing sodium silicate and sodium aluminates is another method of preparing permutit.
Permutit is in the from of a porous gel.
The principle involved in this process is to convert the dissolved salts of calcium and magnesium into insoluble calcium and magnesium permutits, respectively.
This is done by exchanging the base ion radicals such as Ca++ and Mg++ with the base ion Na+ of sodium aluminium silicate.
Hence this process is also known as ‘base exchange process’.

This is carried out by passing hard water through the layers of zeolite or permutit. This method removes both temporary hardness and permanent hardness.

Permutit process removes temp. as well as permanent hardness.

In the permutit process, there will be a column in which gravel, sand and permutit are placed in alternate layers.
Hard water is made to rise up through the various layers.
As water passes through the permutit, the ions of calcium (Ca++) and magnesium (Mg++) which causes hardness are exchanged with the sodium ions of the permutit.
Permutit is changed eventually into calcium aluminium silicate and magnesium aluminium silicate.
These are called calcium permutit and magnesium permutit respectively. We shall discuss two examples to understand how this happens.

Sodium permutit + Calcium chloride " Calcium permutit + Sodium chloride

Sodium permutit + Magnesium sulphate " Magnesium permutit + Sodium sulphate

Water that comes out of the permutit column contains neither calcium ions nor magnesium ions.
However, the water softened by this method contains sodium ions.
The presence of these ions, however, will not make water hard.
Permutit process is an economical way of softening water.
The hardness is more or less completely removed by this method.
This method is not so appropriate if the hard water contains sodium salts or suspended matter in large quantities.
Lead, if present in water, is not removed in this method.
The permutit process is useless if the water contains iron or manganese impurities.
What we get through permutit process is only soft water and not pore water.

Justify 
Pure water is soft However, soft water need not be pure. It this possible ? How ?

Types of hardness, water for std 8 to 10 CBSE

TYPES OF HARDNESS
Depending on the kind of negative ions present along with Mg++ and Ca++ ions, hard water is classified into two types namely temporary hard water and permanent hard water.
The water that contains bicarbonate ions along with Mg++ and Ca++ ions could be softened by mere boiling. Hence, such water is called temporary hard water.
The water that contains chloride or sulphate ions along with Mg++ and Ca++ ions is called permanent hard water.
This means the hardness causes by dissolved magnesium bicarbonate and calcium bicarbonate is temporary hardness.
The hardness caused by dissolved magnesium chloride, calcium chloride, magnesium sulphate or calcium sulphate is called permanent hardness.
Water samples may contain more that one salt that causes hardness.

DISADVANTAGES OF HARD WATER
We use water daily for a number of activities such as washing clothes, cleaning utensils, bathing, drinking, cooking and so on.
Hard water is not so suitable for these activities.

1. Pulses and vegetables are not cooked properly in hard water.
2. Hard water used for bathing makes the skin dry and leaves a whitish residue on the skin.
3. The utensils lose shine and get stained when washed with hard water.
4. Hard water is not suitable even for washing. Clothes are not cleaned in hard water.
5. Soap is also wasted.
6. The salts present in hard water from a yellow stain on clothes.
7. The salts accumulated on the inner walls of the cooking utensils makes their cleaning difficult.
8. It also wastes fuel energy.

Hard water causes in Industrial pipe lines etc.

Video presentation 

how hard water develops insoluble carbonates in pipes 

• Hard water poses many problems in industries such as paper, dye, printing, textiles, sugar etc.
• Hard water forms a scale on the inner walls of industrial boilers.
• Why does hard water causes scales on the walls of boilers ?
• Hard water usually contains dissolved bicarbonates.
• The dissolved bicarbonates, on boiling, dissociate to form insoluble carbonates which go on depositing on the inner walls of the boiler.
• This results in scaling.
• The scale not only corrodes the boiler but wastes fuel as well.
• Hard water sometimes causes foaming and explosions of the boiler. 
• The scales formed inside the pipes reduce the size of the pipes and corrode them (fig). 
• Therefore hard water is not suitable for use in boilers.
• Hence we need to soften water and then use it. 
• There are many methods of softening water.
• Some methods remove only temporary hardness while others remove both types of hardness.

Activity
Take some amount of hard water in a glass beaker and boil it. Allow the water to cool. Observe the walls of the beaker closely. Repeat the experiment with soft water. What difference do you notice ? Why ? Explain.

Examining impurities in glass

Water Science for std 8 to 12 CBSE, GSEB

WATER

Hard and soft water – experiments with hard water – removal of hardness – conservation of water.

REVIEW

You have studied many aspects of water in your previous classes. Water is a wonderful substance. It is one of our invaluable resources. Without it life can neither exist on earth nor can the bio-chemical reactions take place. Let us once again recall some of the important points that you have already studied about water.

Water is a compound made of hydrogen and oxygen.

Most of the land on earth is Covered with water.

Water exists on earth in all the three states – solid, liquid, and vapor.

Water can dissolve the highest number of substances in it.

Most of the substances that dissolve in water are inorganic ionic compounds.

The ionic compounds dissociate into positive and negative ions when dissolved in water.

Seawater is saline and hence not potable. Distillation is a method of obtaining pure water from seawater.

Even distilled water is not potable.

Water gets cycled continually through the biosphere and this movement is called water cycle.

Water sources are being polluted due to human activities.

Indian philosophers regarded water as one of the five elements that constitute the universe. Even the westerners had similar views. A British chemist, Sir Henry Cavendish showed for the first time in 1781, that water is produced when hydrogen burns is air. Lavosier, a Frech chemist proposed that water is not an element but a compound made of hydrogen and oxygen.

INTRODUCTION

The water obtained from natural sources have several salts dissolved in it. Salts such as nitrates, sulphates, chlorides, and bicarbonates might have been dissolved in water. Pure water has neither color and taste nor smell.

Water gets colour, teste, and smell due to impurities. Water acquires certain properties other than colour, taste and smell, when certain salts are dissolved in it. The change in the way it interacts with soap is one such property. Based on the way in which it acts with soap, water is classified as soft water and hard water.

Note

Rainwater dissolves small amount of atmospheric carbon dioxide in it to form a weak acid called carbonic acid. The other chemicals that are let into the atmosphere may also e dissolved in it. Hence even rainwater is not pure.

SOFT WATER AND HARD WATER

Water that gives lather with soap easily and readily is called soft water. Pure water is always soft. Water may be soft even when some salts are dissolved in it.

Experiment 1 : 

Collect samples of water from different sources – tap, bore well, pond or lake etc. Take equal quantity of the samples collected in different test tubes. Add about 1 gram of soap powder to each of them. Shake well. Which of them gave lather easily and spontaneously ? Which sample does not give lather readily ?

Experiment Soap formation in different water

Experiment of soap formation in different water

Experiment 2 : 

Collect samples of water from various sources as mentioned in the experiment cited above. Add 1 gram of soap powder to each of them and stir until the soap dissolves in water. Now blow the contents of each of the test tubes using a straw few times. Which of them gives lather profusely ?

Experiment of soap by air in different water sample

Experiment of soap by air in different water sample

Experiment 3 : 

Does the water you use at home give lather readily with soap ? Test and find out.

Experiment 4 : 

Take equal quantities of water in two beakers. Add about 1 gram of calcium chloride to one of them and stir well. Now add about 1 gram of soap powder to each beaker. Blow the contents of the beakers using a straw. Which of them give lather well ? Repeat the experiment by using sodium chloride, sodium bicarbonate, magnesium chloride, calcium sulphate, and magnesium sulphate instead of calcium chloride. Which of them give lather ? Which of them does not give lather ? Examine.

Test of water with different substance like Calcium Chloride

Test of water with different substance like Calcium Chloride

Test of water with different substance like Calcium Chloride

It is not practically possible to obtain calcium bicarbonate and magnesium bicarbonate in solid form. This is because these salts chemically dissociate much before the evaporation is complete and form their respective carbonates.

Therefore, it is only possible to have solutions of calcium bicarbonate and magnesium bicarbonate.

Certain salts dissolved in water from a scum with soap. Water that forms an insoluble scum with soap before giving lather is called hard water. Hard water does not readily give lather with soap. The dissolved salts such as calcium bicarbonate, calcium sulphate, calcium chloride, magnesium bicarbonate, magnesium sulphate and magnesium chloride are the chief salts that cause hardness of water. Let us consider how these salts render water hard.

Note that the salt that cause hardness are ionic compounds. These salts ionize to give positive ions and negative ions when dissolved in water. For example, magnesium sulphate when dissolved in water, dissociates into Mg++ ions and SO4- ions. Similarly calcium sulphate (CaSO4) dissociates into Ca++ and SO4-. The equations showing the process of ionization of salts causing hardness of water, are given below.

The salts that cause hardness in water include calcium fluoride and salts of iron. Ions of iron and manganese will also cause hardness of water.

MgSo4                -         Mg++         +       SO4 --

CaSO4                -         Ca++          +       So4--

CaCL2                -         ca++           +       So4--

MgCL2               -         Mg++         +       2CL-

Ca(HCO3)2        -        Ca++          +       2(HCO3)-

Mg(HCO3)2       -        Mg++         +       2(HCO3)-

Of the ions mentioned above, only Mg++ and Ca++ ions cause hardness. These ions form an insoluble scum with soap. How does hard water form scum with soap ? Soap (you will know more about it later) is a sodium salt or potassium salt (Ex: sodium stearate or potassium stearate repectively). These salts react with Mg++ and Ca++ ions present in water to form magnesium stearte and calcium stearate respectively. These insoluble precipitates, from a scum on the surface of contact. Soap begins to give lather only after all the Mg++ and Ca++ ions present in this water samples are precipitated.

CERAMICS the synthetic material for std 8 to 12

Ceramic Pot

Ceramics :

Clay materials, such as chinaware, porcelain and bricks, are collectively known as ceramics.
All these are being traditionally manufactured and used for over several centuries.
The word ceramic is derived from a Greek word ceremos which means earthen pot.
Preparation of porcelain : 

The raw materials required for the preparation of porcelain are whit clay, sand and feldspar [K2O AI2O3 6SIO2].
Finely powdered mixture of raw materials are mixed with water.The homogeneous mixture is called slip. Slip is pressed with filter paper to remove excess water. Then the slip is moulded into desired shapes and dried. The dried articles are heated in a furnace at about 1873K.
Remember
Clay is the mixture containing aluminium silicate in high quantities. It is formed by the weathering of silicate rocks by the action of air, rain and corbon dioxide.
The fired articles are porous.
These pores are plugged by glazing.
Glazing imparts an attractive look.
Chemicals like born, alumina and smooth silica the uniform spreading of coat.
Pre-determined quantity of metal oxides are added while glazing.
Which gives desired colour to the porcelain.
Uses of porcelain : 

Household articles. Decorative materials. Insulating parts of electric devices. Sanitary items and Laboratory equipments.

Porcelain uses

POINTS TO REMEMBER

Synthetic materials are manufactured by using natural raw materials.
Synthetic materials are plastics, cement, glass, fibers and ceramics.
Polymers are compounds formed by the union of many simple monomers.
Polymerisation is a process of uniting two or more simple compounds to obtain a new compound.
Addition polymerization is a process in which several molecules join together to form a giant molecule.
Polythene, polyvinyl chloride and nylon are examples for polymers.
Plastic is a synthetic material manufactured by polymerization of organic substances.

Polyvinyl chloride and polystyrene are thermoplastics.
Bakelite, silicones are thermosettings.
To avoid the hazards of plastics the usage of plastics should be abandon stage b stage.
The raw materials of cement are clay, lime stone.
Gypsum slows down the rapid setting of cement.
The method of hardening of cement by treating with ater is known as curring.
The raw materials used in the manufacture of glass are sand, limestone and sodium carbonate.
The different types of glass are soda glass, borosilicate glass, lead glass.
Coloured glass, safety glass and fiber glass.
The process of slow cooling of glass is known as annealing.
The raw materials of ceramics are whit clay. Sand and feldspar.
Porcelain is used to prepare decorative materials.
Glazing imparts an attractive look and also plug the pores.

Glass as synthetic materials CBSE for std 8 to 12

GLASS

Glass Synthetic Material

Glass is one of the oldest synthetic substances being used.
Due to its transparent and non-corrosive property, glass is widely used in various fields.
Chemically glass is a homogenous mixture of sodium silicate and calcium silicate (Na2SiO2, CaSiO3, 4siO2)
Note
Even though glass is a transparent material, all the raw materials used are opaque in nature.

Manufacture of glass : 

Sand, limestone and sodium carbonate are the raw materials required for the preparation of glass.
Scrape glass is also used along with other raw materials. Hence recycling of glass is also done.
A finely powdered mixture of raw materials is introduced into a furnace maintained at a temperature of about 1973K.
Raw materials fuse and combine chemically to form a mixture of calcium silicate and sodium silicate.

Do you know ? 
Glass articles are prepared by blowing method. A small amount of glass is fixed to the end of a long blowing pipe and heated. A small bulb is formed when air is blown from the other end. By rotating the pipe, the required shape is given to the glass. The glass bulb is kept in a mould and blown again to acquire the required shape. 

sodium Silicate reaction

The molten glass is cast in the mould or blown into various shapes and cooled slowly.

On slow cooling, glass gains the capacity to withstand stress and loses brittleness.
The process of slow cooling of glass is known as annealing.

Note this
To remove the air bubbles in glass, borax or aluminium powder is added to the glass and heated slowly. The air bubbles escape from the glass in this process.

Properties of glass : 

Glass is a strong and transparent material.
It is corrosion resistant.
It does not react with other chemicals at ordinary temperature.
It gradually softens on heating, and begins to flow very slowly.

The following table gives the different types of glass, their properties and uses.

Different types of glass and their properties

Different types of Glass and their properties

Soda Glass Figure :

Soda Glass

Soda Glass with soda

Borosilicate glass

Borosilicate glass

Borosilicate glass

Borosilicate glass

Borosilicate glass

Lead glass

lead Glass

Lead Glass

Coloured  glass

Coloured  glass

Coloured  glass

Coloured  glass

Thanks to google image provider