Chemical Fun 3t3a4q

Feature Article

IQBAL ABDUL DHALAIT

Fun With Chemistry! E

VERY day we come across many changes in our surroundings. These changes may involve one or more substances. For example, your mother may ask you to dissolve sugar in water to make a cold drink. You would also be familiar with the rusting of iron in which oxygen molecules from the atmosphere react with iron atoms in presence of moisture to form a new substance. The atoms in iron oxide line up differently from those in either oxygen molecules or iron. Again, if we look at photosynthesis, plants use the energy in sunlight to together six molecules of carbon dioxide and six molecules of water to produce one molecule of glucose and six molecules of oxygen. We drink potable water from the tap or from a bottle. We may also drink it as lemonade or fruit juice, tea or coffee. This water has unique properties because of the way in which its molecules cling to each other. It is an oxide of hydrogen, just a chemical but remarkably unusual. Just add a single oxygen atom to it and it becomes hydrogen peroxide with absolutely different properties. Isn’t it all so curious? Chemical reactions happen naturally or can be made to happen; they may take years or only an instant. Here are some reactions laid down before you. Try them at home and enjoy the fun.

peroxide, ammonium hydroxide, hydrochloric acid, potassium iodide, liquid detergent, Tincture of Iodine, sodium thiosulphate, Phenolphthalein pH indicator, ethyl alcohol, water, potassium permanganate, glycerin, ammonium thiocyanate, ferric chloride silver nitrate, potassium ferrocyanide, ferric chloride, sodium hydroxide.

1. Change Coca Cola into Water Let us suppose you have invited two guests to your place and one of them is interested to have Coca Cola while the other wants plain water. Now, your predicament is that although you have a bottle of Coca Cola, you do not have drinking water. Strange situation, but let’s go along with it. Now, can you please both of them by pouring Coca Cola for one from a Coca Cola bottle and plain water for the other from the same bottle? Impossible? Well, just perform this simple chemical trick not for actually drinking purposes but just to impress your guests. Prepare Coca Cola chemically by mixing sufficient quantities of Tincture of Iodine in water so as to get dark colour similar to the Coca Cola drink, store it in a soft drink bottle and seal it properly well in advance. Take two empty glasses, put some crystals of sodium thiosulphate in one glass well in hand.

Now, open the Coca Cola bottle in front of your guests and pour some of the liquid in the empty glass, you will get Coca Cola. Then pour the remaining liquid from the same bottle in the other glass containing crystals of Sodium thiosulphate. This time you will get plain water. The crystals of sodium thiosulphate (hypo) react chemically and decolourise the liquid when it is poured in the glass. The coloured liquid dramatically becomes as clear as water!

2. The Crazy Message Take a blank white paper and write any message with phenolphthalein indicator using cotton bud and allow it to dry. Fill the spray bottle with ammonium hydroxide solution and spray this solution directly on the watery marks on the paper. The invisible message written on the paper will begin to appear in colour and you will be able to read it. But interestingly, after a few minutes the colour message will start to fade away and finally completely disappear. Due to the alkaline nature of ammonium hydroxide, phenolphthalein gives a pink colour when it is allowed to mix with the solution. Further, on exposure to room temperature the ammonia evaporates from ammonium hydroxide leaving the water particle behind on the paper which is colourless in phenolphthalein indicator. In this way the message disappears to your great surprise.

What will you require? An empty soft drink bottle, drinking glasses, jug, conical flask or transparent plastic bottle, rubber cork, rose flower, plate, paper cup, handkerchief, metal plate/ ceramic plate, knife, cotton bud, blank white paper, cotton swab, match box, pairs of tong, glucose powder, methylene blue indicator, sulfur powder, hydrogen

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SCIENCE REPORTER, APRIL 2011

Feature Article First ethyl alcohol starts to burn since it has a low boiling temperature as compared to water. Water acts like an absorber 3. The Unburnable Handkerchief Ask your friend to give you his handkerchief and get his kind permission to burn it. Hardly likely that you will get the permission. Well, you can perform this trick with your handkerchief. Dip it in a mixture of ethyl alcohol and water prepared in the ratio of 1:1. Squeeze out the excess liquid and hold it with pairs of tong and then put on the candle flame. You will be surprised to notice that the handkerchief catches fire without actually burning. When you put the handkerchief on fire, first ethyl alcohol starts to burn since it has a low boiling temperature as compared to water. Water acts like an absorber and absorbs the heat released by burning the ethyl alcohol helps to keep the temperature of the cloth down so that it does not catch fire. If your friend has been bold and trusting enough to hand over his handkerchief, you can now return the handkerchief without any damage done.

4. Create Fire Magically Place a metal /ceramic plate on a table. Put a piece of paper with some potassium permanganate ground in powder form in

the centre of this plate. Arrange some pieces of paper on a metal plate. Put two or three drops of glycerin over potassium permanganate. The glycerin will slowly start to react with this black powder by giving off smoke and very soon the pieces of paper will start to burn with violet flame. This is an example of exothermic reaction in which heat is produced and it is sufficient to burn the paper pieces. Unscrupulous people often use this trick to demonstrate their “supernatural” powers. But now you know it is just a simple chemical trick.

Cut Your Hand Painlessly Moisten your hand with a solution of ammonium thiocyanate and apply ferric chloride solution with cotton on the knife blade. Now begin your demonstration.

5. Cut Your Hand Painlessly Can you dare to cut your hand with a knife? Well, try this simple chemical trick to impress your friends. First, before you begin your trick moisten your hand with a solution of ammonium thiocyanate and apply ferric chloride solution with cotton on the knife blade. Now begin your demonstration. Hold the knife and press the reverse edge, the blunt edge, of the knife against your skin where ammonium thiocyanate has already been applied. At once a blood like liquid will flow out of the mark made by the blade as ammonium thiocyanate and ferric chloride react. It will seem as if you have actually cut your hand and the wound is bleeding.

6. Tri-Colour Change You must be familiar with the phenomenon of a turmeric stain on a white shirt turning red when it is washed with soap. This happens simply because of the alkaline nature of the soap solution. This chemical reaction is another example of colour change. If you know how to do it, you can easily turn water into soft drink, milk or even ink.

Prepare solutions such as ammonium thiocyanate, silver nitrate and potassium ferrocyanide by dissolving about a spoonful of these chemicals into 50 ml water respectively. Take about 10 drops of each solution in three glasses and arrange them side by side on the table. Prepare another solution of ferric chloride of the same concentration. Mix it with three glasses of water in the jug. Just pour the liquid from the jug into the first glass and you will get red colour resembling the soft drink. You will get milk in the second glass and blue ink in the third glass. The change of colour to red and blue are familiar tests for ferric ion that was already present in the solution. The white precipitation is a common test for chlorides. Silver nitrate reacts with ferric chloride to form a thick white precipitate of silver chloride resembling milk.

7. Shake It to Get Blue Colour Oscillating reactions are truly spectacular because of the visual display exhibited by these reactions. Here is one of such reaction that can be performed with common chemicals. Fill three fourth of a conical flask or transparent plastic bottle with water. Add about 5 grams sodium hydroxide in it. Add 5 grams of glucose powder and then put SCIENCE REPORTER, APRIL 2011

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Feature Article Now take this flower out of the glass. Fill the glass halfway with hydrogen peroxide and dip the rose into it. It will start to gain its original colour. The sulfur dioxide which is produced by burning sulfur combines with oxygen from the coloured part of the flower leaving the flower bleached white. The bleached flower is then dipped in hydrogen peroxide which provides oxygen to the flower restoring its colour.

9. Create Smoke without Burning a few drops of methylene blue indicator to this solution and shake them to mix the dye. The resulting solution will be blue. Hold and keep the solution steady and observe any change in colour. The liquid will gradually become colourless as glucose reduces the methylene blue dye and the colour of the solution disappears. Can you restore this colour again? To do this just shake the contents of the conical flask very rapidly by capping the mouth of the container with cork, you will be surprised to see blue colour again. This is due to re-oxidation of methylene blue with oxygen from the trapped air. The reaction can be performed several times by standing and shaking alternately to make it happen again and again.

Take a glass, moisten the inside of the glass with ammonium hydroxide. Take a few drops of concentrated hydrochloric acid on the plate. Invert the glass over the plate. Fumes will start to accumulate in the glass.

8. A Rose of Changing Colour

The vapors of ammonia combine with hydrochloric acid to form dense white fumes of ammonium chloride to give the effect of smoke.

Take a fresh rose and moisten it with water. Tape it to the inside of a drinking glass as shown in the picture. Place a small amount of sulfur on a metal plate and allow it burn by providing heat. When it begins to burn, invert the drinking glass over the burning sulfur. The flower will start to lose its natural colour and will become white.

You will be fascinated to see the tiny bubbles that make the resulting column of foam that gushes out look more like toothpaste. tiny bubbles that make the resulting column of foam that gushes out look more like toothpaste.

11. Boil Water in Paper Cup What do you think will happen to a paper cup of water when it is held over a candle flame? You would be surprised to know

10. Oxygen Foam Pour 100 ml of hydrogen peroxide into a tall glass cylinder. Add some liquid detergent to it. Mix them thoroughly. Add about a teaspoonful potassium iodide in this mixture to make the hydrogen peroxide break down chemically. This rapid decomposition results in lots of oxygen that turns into foam. You will be fascinated to see the

A Rose of Changing Colour Fill the glass halfway with hydrogen peroxide and dip the rose into it. It will start to gain its original colour. 31

that the paper cup will not burn. Let us see how it is done. Fill three fourth of a paper cup with water. Hold the cup a few centimeters above the candle flame. The paper cup held over an open flame will not burn because the heat from the flame transfers from the cup to the water. Thus the paper never gets hot enough to burn. Instead, the transferred heat causes the water to boil!

Mr Iqbal Abdul Dhalait is an Education Officer with the Goa Science Centre, Miramar, Panaji-Goa; Ph: (0832) 2463426 SCIENCE REPORTER, APRIL 2011