Alloys and Its Advantages

You may have seen utensils made up of stainless steel. Do you know that stainless steel is not a pure metal ? It is a mixture of iron, chromium and nickel. Stainless steel is an example of a class of substances called alloys.

An alloy is a homogeneous mixture of two or more metals (or a metal and small amount of non metals)

For example, one type of brass is two - thirds copper and one - third zinc. Steel is an iron containing carbon (from about 0.25% to 1.5%)

Alloys are widely used in construction purposes.

An alloy is generally preferred to a pure metal when it has some special property - stainless steel does not rust; gold alloys tend to be harder than pure gold; brass and bronze have more attractive colour than the pure metals from which they are made and duralumin has far greater strength than pure aluminium.

The first alloy formed was bronze. It is an alloy of copper and tin. Bronze is a popular metal for making bells and musical instruments such as cymbals, and saxophones. Bronze is also used for making sculptures.

1.0Advantages of Alloys 

(i) Alloys can be made stronger, more malleable, better- conductors more resistant to corrosion and tougher than the parent metal. For example, stainless steel has a high resistance to corrosion. The steel contains iron and a low percentage of carbon.

(ii) The composition of alloys can be manipulated according to our needs. Here are a few examples to illustrate this advantage. 

(a) Iron mixed with a small amount of carbon gives steel, while iron mixed with chromium and nickel gives stainless steel which has properties different from that of steel.

(b) Bronze consists of copper with about 10% tin. If a greater proportion of tin is used, the alloy is harder than an alloy with less tin.

(c) When copper is mixed with zinc, the alloy obtained is brass, which has a more attractive colour than either pure copper or pure zinc. If the amount of zinc is less than 36%, the alloy is ductile, when cold and can be worked into complex shapes without the necessity of re-heating. With more zinc, a harder stronger alloy is obtained. 

2.0Useful Solutions and Compounds

Solutions

Solutions are homogeneous mixtures. In a solution, the component present in large amounts is called the solvent, and the component present in small amounts is called the solute.

The liquids we usually drink, and the fluids present in our body are all examples of solutions. The biological importance of the solution is that life cannot exist without it. The solvent properties of water make the survival of the living organisms possible. All substances essential for the functioning of the cells and organisms are transported around in blood, a solution.

The most common solutions that we consume are tea, coffee and aerated drinks. Let us discuss some of them here.

Soda water 

Soda water is basically carbonated water. It is prepared by dissolving carbon dioxide in filtered water under high pressure. Modern trends in making soda water includes adding flavour to it without adding sugar. Soda water refreshes us when we feel tired.

Soft drinks

Soft drinks are beverages consisting primarily of carbonated water, sugar and flavours. Soft drinks under different brand names are available in the market.

Syrups

A syrup is a thick, viscous liquid containing dissolved sugars and natural or artificial flavours. Some syrups (sharbat) when diluted with water or milk form very refreshing drinks, and they are usually taken during summers. Some of the medicines are also available in the form of syrups.

Saline (medicine)

In medicines, saline is the term generally used for a sterile solution of sodium chloride in water. This is mainly used for intravenous infusion. Intravenous infusion is used for supplying extra water or salts and water to the patients who are unable to take them by mouth. These intravenous solutions mostly have glucose added to them.

It is very important to know that all reactions take place in a medium. All the chemical reactions in our body take place in a solution. The most common medium where all reactions take place is water.

Compounds

There are millions of compounds known to us. All of them are useful in some or the other way.  They are either naturally occurring or artificially prepared. Compounds are broadly classified into two types on the basis of composition. They are,

(a) Inorganic compounds and

(b) Organic compounds

Inorganic compounds are those which are obtained from minerals such as common salts, hydrochloric acid, sulphuric acid, caustic soda, slaked lime etc.

Organic compounds are those which are obtained from living organisms, plants and animals. They all contain carbon in them, and oxides of carbon are not organic.

3.0Use of Few Compounds Are Mentioned Below 

1. Washing soda : It is used for washing clothes. It is because of this chemical used that the clothes washed by a washerman appear so white. Chemically, washing soda is sodium carbonate decahydrate (Na₂CO₃.10H₂O). It is an important chemical required as basic raw material in hundreds of industries.

Uses : Washing soda is used in the manufacture of glass, water glass, caustic soda, borax and soap powders. It is also used for softening of water, as laboratory reagent and as a starting material for the preparation of a number of other sodium compounds. Of course, its most common use in laundry is for washing of fabrics and clothes from which it gets its name.

2. Baking soda : You must have seen your mother using baking soda while cooking some dals. If you ask her why she uses it, she would say that it helps in cooking some items faster, otherwise it would take much longer time. Chemically, baking soda is sodium hydrogen carbonate or sodium bicarbonate and its formula is NaHCO₃.

Uses : Baking soda is mainly used in the baking industry. When sodium hydrogen carbonate or its solution is heated, it gives off carbon dioxide.

It is this carbon dioxide which raises the dough during baking. The sodium carbonate produced during the heating of sodium hydrogen carbonate gives a bitter taste. Therefore, usually baking powder is used, which is a mixture of baking soda, sodium hydrogen carbonate soda, NaHCO₃ and an acid like tartaric acid. The latter is added to neutralize the sodium carbonate formed in the reaction given above, to avoid its bitter taste.

You must have eaten cakes. They are made so soft and fluffy by using baking powder. Baking soda is also used in medicines to neutralize the excessive acidity in the stomach. Mixed with a solid acid such as citric (C₆H₈O₇) or tartaric acid, it finds use in effervescent drinks used to cure indigestion.

Another important use of baking soda is in certain types of fire extinguishers.

3. Bleaching powder : Have you ever wondered at the whiteness of a new white cloth? How is it made so white?

It is done by bleaching the cloth at the time of its manufacture. Bleaching is a process of removing colour from a cloth to make it whiter. Bleaching powder has been used for this purpose since long. Chemically, it is calcium oxychloride and its formula is CaOCl₂. 

Uses : It is used mainly for bleaching cotton, linen and wood pulp in textile and paper factories. Apart from this, it is used as a disinfectant and germicide for the sterilization of water, in rendering wool unshrinkable and for the manufacture of chloroform. It also finds use as an oxidizing agent in many chemical industries.

4. Plaster of Paris : You must have seen beautiful designs made on the ceiling and walls of rooms in many houses. They are made with Plaster of Paris, also called POP.

Uses : Plaster of Paris finds use in making casts and patterns. It is used for making plaster casts to hold fractured bones in position while they set. It is also used for making chalks for writing on a blackboard. Nowadays it is increasingly being used for plastering the walls, pillars and ceilings and to make ornamental patterns on them.

5. Sodium chloride (Common salt/table salt) 

Sodium chloride (NaCl) which in common language is also known as common salt. This is the salt which you sprinkle on your salads and use in your kitchens. Common salt is a compound of sodium and chlorine (Na⁺Cl^–)n. The main source of common salt (sodium chloride) is sea water. Sea water contains about 3.5% of soluble salts, the most common of which is sodium chloride (2.7 to 2.9%). Saline water of inland lakes, such as Sambhar Lake in Rajasthan is also a good source of common salt. Sodium chloride is also found as rock salt. Beds of rock salt were formed when lakes/seas dried up in the past. Common salt acts as raw material for making various materials of daily use.

Uses of sodium chloride (common salt): 

It is a white crystalline solid. It is soluble in water. It is also known as table salt. It is mainly used in-

In food: Sodium chloride is an important part of our diet as it is essential for the proper working of the nervous system.

In the chemical industry: It is used in the manufacture of chlorine gas. It is also      used for making compounds of sodium such as washing soda and sodium hydroxide.   

As a food preservative: Salting of meat and fish prevents them from spoiling.

4.0Some More Useful Compounds and Solutions

(1) Tea and coffee are solutions of the soluble content of the tea leaf and coffee bean. Some add sugar which dissolves to give these drinks a sweet taste.

(2) Soda water is a solution of carbon dioxide in water with a slight acidic taste. 

(3) In cooking, salt is usually added at some stage and it goes into solution. These solutions that we use are less important than the essential intake of water. We require water for many purposes because the chemical reactions in our bodies take place in solutions.

(4) Aluminium oxide is the source of aluminium from which our cooking utensils are made.

(5) While cooking our food, common salt (sodium chloride) is added. Sodium chloride (common salt) is used in the electrolysis of brine (water saturated with salt) to produce sodium hydroxide, which is used in soaps, paper and rayon.

(6) To get better yields for the food crops, all kinds of fertilizers are used - potassium nitrate, ammonium nitrate, ammonium sulphate and various phosphates. Some of the crops, for example, potatoes may be protected from attack by fungus using Bordeaux mixture. This fungicide is a mixture of copper sulphate and calcium hydroxide (slaked lime).

(7) Calcium carbonate (limestone) as marble is useful for decorative purposes. More importantly, in the extraction of iron, limestone helps to remove impurities. It is also required for the manufacture of cement. Also, when strongly heated, limestone decomposes to give lime (or quicklime - calcium oxide).

(8) Treating lime with water gives slaked lime, the solution of which is known as limewater.

(9) Gypsum is the common name of calcium sulphate -2- water. When heated, gypsum loses three - quarters of its water forming plaster of Paris. The most obvious use of Plaster of Paris is the plaster cast supporting broken limbs and keeping the bones together for healing to take place.

(10) Zinc oxide is used as a white pigment in paints.

5.0Complex Organic Compounds

The major food groups are carbohydrates, fats and proteins. These are all complex organic compounds. The chemical process of digestion breaks down these complex compounds into simple molecules. These molecules can be absorbed into the blood stream, carried to wherever required and re-built into carbohydrates, fats, and proteins.

A brief description of carbohydrates, fats, and proteins is given below.    

Note : Carbohydrates got their name from the molecular formulae which can be written, as the molecules were simple combinations of carbon and water. For example, Glucose C₆(H₂O)₆ and Sugar (Sucrose) C₁₂H₂₂O₁₁. Glucose is used as a source of instant energy.

Just as carbohydrates and fats provide energy for the body, much simpler organic compounds are used as the source of domestic and industrial energy. These are hydrocarbons which contain carbon and hydrogen only. The simplest hydrocarbon is methane (CH₄). This gas is used as a fuel in the form of CNG (Compressed Natural Gas). The other common fuels - petrol, diesel, LPG and kerosene are also hydrocarbons.