Change renders life dynamic. Look around you and you will see changes occurring every moment. A peeled apple for instance turns pale brown when exposed, incense sticks disappear on burning leaving behind sensations of their fragrance, naphthalene balls disappear, sugar dissolves in water, children grow, etc. Some of these changes are reversible and others are irreversible. A cup for instance drops on the floor and breaks into pieces, even this is a change, and you don’t see the pieces gathering together and re-uniting spontaneously and rising to its previous position on the tabletop, perhaps. Nor do you find a man or women reverting to childhood physically after some period of adulthood. Funny, isn’t it?
Imagine how the world would be if changes were reversible. Perhaps you could then go back into the past, were it glorious or dive into the future. How would you define History then?
But for now I shall not dwell on the scope of Thermodynamics – the branch of chemistry dealing with Spontaneity of changes within its providence. I shall tell you of changes you can have fun with.
But you must remember that some of these experiments are hazardous and should be performed very cautiously and under the supervision of a teacher in a lab.
Blood in a Lemon
Will you ever dare to cut your hand? A loud NO. But now try this without feeling plain. Take a knife with a wooden handle. Rinse the knife blade with ammonium thiocyanate solution and apply some ferric chloride solution on a whole lemon piece. Now press the knife blade against the lemon as you would do to cut it into halves. What do you see? As the knife finds its way through the lemon cautiously enough, red drops of blood ooze out from the junction of the cut. It is due to the reaction between ferric chloride and ammonium thiocyanate. Interested chemistry learners can find out the reaction if you wish to.
Magic with Colours
Remember magicians are chemists in action. So you could also become a magician momentarily at least. Let’s play with colours. Take a fresh rose and moisten it with water. Tie it to the inside of a drinking glass. Place some sulphur on a metal plate and heat it to burn. When the sulphur starts to burn, invert the drinking glass over the burning sulphur. The flower will start to lose its colour and will become white. Now remove the flower from the glass. Fill the glass halfway with hydrogen peroxide and dip the rose into it. Gradually the rose will get back its original colour.
Pour about 200 ml of hydrogen peroxide into a tall glass cylinder. Add some liquid detergent to it. Mix the contents thoroughly Add two spoonful potassium iodide into this mixture You will be fascinated to see tiny bubbles making up a column of foam that gushes down the sides of the cylinder.
Chemistry is Colourful
Most of the chemistry students, especially at the secondary level simply love to run to the laboratory to see colour changes. Try this game.
You must have noticed that orange yellow turmeric turns red in contact with soap water. See if you can change the colour of water! Take about a spoonful of ammonium thiocyanate, silver nitrate, and potassium ferrocyanide separately in three 50ml glass beakers. Take about 10 drops of each solution in three glasses and arrange the glasses separately side by side on the table. Prepare another aqueous solution of ferric chloride of the same concentration in a jug. Add about three glasses of water to the ferric chloride in the jug. Now pour the liquid from the jug into the first jug and you will see red colour resembling soft drinks. The second glass looks white like milk and a blue inky solution appears in the third glass. The change of colour to red and blue are due to the ferric ions present in these solutions. The white precipitation is a characteristic test for chloride ion. Silver nitrate reacts with ferric chloride to form a thick white precipitate of silver chloride resembling milk.
Place a metal or ceramic plate on a table. Put some potassium permanganate, in the finely divided powdered state, along with bits of paper at the centre of this plate Pour two to four drops of glycerine over the potassium permanganate. The glycerine will slowly react with the powder to give out smoke and the paper bits burn with a beautiful lilac flame. Exothermicity of the reaction produces sufficient heat to burn the paper. You could also create smoke without fire but using ordinary cold water. Guess how?
An Unburnable Handkerchip
You would never like to burn your handkerchief. But perform this trick. Take your favourite handkerchief and dip it into a mixture of ethyl alcohol and water in the ratio of 1:1. Squeeze out the excess liquid and hold it with a pair of tongs over a candle flame. To your surprise you will find the handkerchief catching fire without actually burning.
Actually, the ethyl alcohol which is inflammable with a low ignition temperature starts to burn, unlike water. Water acts like an absorber and absorbs the heat released by the burning ethyl alcohol to keep the temperature of the cloth down so that it does not catch fire.
Paper is reduced to ash when held over fire. But just fill three fourths of a paper cup with water and hold it obliquely over the flame. You will find that the cup does not catch fire even though the water starts to boil. Actually heat is transferred from paper to water by conduction and subsequently convection sets the water to reach boiling. But the paper never gets enough heat to burn itself.