Friday, March 4, 2011


                                                 CHEMICAL    SNOWFALL
This Fascinating experiment is based on the sublimation property shown by Benzoic acid.
·         A glass rectangular chamber
·         Sand or mud
·         Tripod  stand
·         Spirit lamp
·         Wire gauge
·         China dish
·         Benzoic acid
·         Some green plants with leafy branches and toy huts
Take  a glass rectangular chamber with wooden base. You can construct it by fixing the four glass walls and glass ceiling on the wooden base. Leave some space between any two edges while joining them together so that air can circulate well inside the glass chamber facilitating the burning of benzoic acid. Now spread a thick layer of wet sand or mud over the wooden base to give the appearance of land. Now place a tripod stand with a spirit lamp below it at one corner inside the chamber. Place wire gauge over the tripod stand and put a china dish over it it containing some benzoic acid.
Now insert the green plants or leafy branches here and there into the thick layer of sand inside the chamber giving the appearance of natural location of snowfall. You can also place some small wooden huts or toys over which the snowflakes of Benzoic acid will settle down to give the realistic view of snowfall.
Now put the flame on at spirit lamp and observe the shining white Benzoic acid crystals directly going into the vapour state .
As these vapours of Benzoic acid fall and touch here and there inside the chamber, they soon get solidified giving the appearance of snowfall over the things inside the chamber. As this sublimation process will speed up, the more dense snowfall will come into the view.                                                
                                                                                                                                                                             pictorial representation of chemical snowfall

              CHEMICAL   HARMONIUM ( Singing flame )
This  experiment is based on the fact that when a flame, as of hydrogen gas or coal gas , burning within a tube is adjusted in such a way so as to set the air within the tube in vibration , it causes sound with different notes with changing  levels of air column inside the tube.
Take some pieces of granulated zinc and put them into Woulfe’s bottle. Now add some dilute Sulphuric acid to this bottle using thistle funnel . Soon the hydrogen gas will start coming out of the delivery tube. Now ignite the hydrogen gas with the help of match stick .
The hydrogen gas will start burning with a blue flame. Now surround this flame with a glass tube about half an inch in diameter with both ends open. Now move the glass tube vertically up and down. A musical sound will be produced. You can set a musical tone just like harmonium d, by continuously moving the glass tube vertically up and down along the flame.
                                                CHEMICAL  SUNSET

 Take two convex lenses and fix them in front of a light source in such a way so that a bright spot of light is obtained on the screen placed in the straight line just after the lenses. Place the entire setup in dark to visualize the effect. Now prepare 10% Sodium thiosulphate solution ( hypo solution ) by dissolving approximately 70 gm in 400 ml of distilled water and fill it in a beaker. Now place this beaker in between the two lenses . Make sure that the light source, two lenses, beaker and the screen should all be in a straight line.

Now add a little dilute hydrochloric acid to the hypo solution placed in beaker. The bright lighted spot on the screen getting cloudy and finally disappears after sometime. This gives the impression of a setting sun. This is what we called chemical sunset.
Mechanism behind this phenomenon :
Diagramatic demonstration of chemical sunset

Picture demonstration of chemical sunset

The above observation occurred due to the precipitation of sulphur from sodium thiosulphate, which makes the solution opaque and light can not pass through.

Tuesday, February 22, 2011


a lemon
 a strip of copper
 a strip of zinc
 a voltmeter
 two cables with alligator clips
 a thermometer or clock with an LCD display

Press the lemon firmly between the palms of your hands in order to break up some of the small sacks of juice within the lemon. Now Insert the two metal strips deeply into the lemon in such a way so that the strips should not touch each other. Using the voltmeter, measure the voltage produced between the two strips as shown above. The reading should be about one volt.
It would be nice to be able to illuminate a light bulb using your new lemon powered battery, but unfortunately it is not strong enough. If you were to try to light a bulb using this setup, the voltage across the strips would fall immediately to zero. Given this, if you want to demonstrate that the current produced by this battery is capable of powering something, try with a small device that uses an LCD display. A clock or a thermometer usually works well. An LCD display consumes an extremely small amount of current and your lemon battery is able to adequately drive this type of device. Remove any conventional battery that is in your clock or thermometer and power it with your lemon battery. You should see the device recommence functioning normally. If not, try swapping the polarity of the electricity from your lemon battery. This system allows you to demonstrate that the battery is producing energy even if you don't have a voltmeter.                                                                                                                                                                                                                                                                                                  
In real commercially-sold batteries, the surface area of both metals is very large and placed very close together to maximize the electricity. The actual amount of electricity you will produce is very small and you will probably not be able to find even a penlight bulb that you can light with this little bit of electricity, but light emitting diodes (LEDs) require less electricity, so you may be able to light a very small one. The liquid crystal displays on electronic calculators use even less electricity (almost none) so you will be able to operate that if you can find one and (with a parent or teacher's help) connect your "lemon battery" in place of the built-in battery.

As a conductive solution, you can use any electrolyte, whether it be an acid, base or salt solution. The lemon battery works well because the lemon juice is acidic. Try the same setup with other types of solutions. You can try this with potatoes, as they contain dilute sulphuric acid in small quantity.

                          CHEMICAL GARDEN   ( silica  garden )

A  Chemical garden is based on the process of crystal growth in 1 %  solution of sodium silicate ( water glass ). It is a garden with non-living plants but is very attractive. Its a beautiful chemical experiment which is based on the phenomenon of osmosis. One more concept is lying here that most transition metal silicates are insoluble in water and are coloured.

Materials you need:

  • One glass jar or aquarium tank
  • Distilled water
  •  sodium silicate solution (1%)
  • chromium (III) chloride hexahydrate crystals (green)
  • Iron (III) chloride crystals (orange)
  • Iron (II) sulphate crystals (green)
  • Copper (II) sulphate crystals (blue)
  • Nickel nitrate crystals (green)
  • Manganese Chloride (  pink )
  • Alum crystals (white)
  • Cobalt(II) chloride crystals (purple)
HOW TO DO THIS :   First of all place a thin layer of sand at the bottom of glass beaker/glass tank. Now prepare 1% solution of sodium silicate in distilled water and pour it into the glass tank. Now drop the crysyals of various coloured salts carefully into this solution leaving a bit of  space between them. In a few hours hollow tubes of metallic silicate gets shootup from these crystals which look like trees. If you add too many crystals the solution will turn cloudy and immediate precipitation will occur. A slower precipitation rate will give you a nice garden. Once the garden grown , you can replace the sodium silicate solution carefully with pure water.
Mechanism behind this : 
  Metal salts of the transition metals, form precipitates when placed in the sodium silicate solution. As the metal salt dissolves, the resulting solution is less dense than the surrounding silicate solution and so rises up through the solution. As it reacts with the silicate anion, 'stalagmites' (like those found in caves) form from the bottom of the tank upwards - these are insoluble metal ion silicates. The surfaces of these insoluble silicates behave as a semipermeable colloidal membrane, across which osmosis can occur.

                                     picture demonstration of silica garden                           

Sunday, February 20, 2011



                                                                  GOLDEN   RAIN
This experiment is based on an instantaneous chemical reaction known as “Gold Reaction”. The bright yellow precipitate is formed by mixing the solutions containing lead(II) ions and iodide ions.
Pb(NO3)2   +  2 KI    ------>      PbI2   +   2KNO3
Two solutions need to be prepared in advance. These are 0.3 wt.% solutions of potassium iodide and lead nitrate. The solutions need to be made strictly in distilled water and make sure that both the solutions should be perfectly colourless before mixing.
Now mix  approximately equal volumes of KI and Pb(NO3)2 solutions in a flask and allow to settle. As a result of this, the lead iodide will precipitate out and get settled at the bottom of flask.
Now decant off the supernatant liquid ( mother liquior) and add the wet precipitate to a similar volume of hot water (70 – 80C) acidified with a little glacial acetic acid in a round bottomed flask. The precipitate will quickly dissolve.   
Now allow the solution to cool down.   After the flask is cooled (under a stream of cold water) beautiful shiny golden crystals begin to form; these slowly fill the flask. If the lamp is allowed to shine on the flask against a black background the crystallisation process appears to the viewers as “golden rain” in a blaze of beautiful      
Colour. The effect is even better if room is darkened.

                                     PHOSPHOROUS  MOON                                                                                                                                                                 
                                 Phosphorous is a very reactive element and unites oxygen with great rapidity.Yellow phosphorus burns in the oxygen to form white vapours of phosphorus pentoxide along with the production of large amount of energy.
In order to make this experiment successful, you need to produce the energy at a rapid speed. so fill a large jar or a round bottom flask with pure oxygen and then light a piece of phosphorus and then seal its mouth.                               You can do as shown in the diagrams below.     
P4 + 10 O2 -> 2  P2O5
Due to this the white vapours of  phosphorous pentaoxide forms here  in the form of  smoke is very hot, so the smoke rises and is rather beautifully lit by the light given off by the flame.
Now the hot phosphorous pentaoxide smoke slowly buids up and cools down.Finally the smoke cools enough that the particles of phosphorous pentaoxide inside the flask makes the still warm air denser than the cold air below and starts sinking down.This sinking produces the beautiful tendrils as the smoke falls and the air rises to take its place.