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.