Page 108 - ICSE Chemistry 6
P. 108

Activity 5.8


                 Aim: To show respira  on in plants
                 Materials required: A conical fl ask, a few germina  ng gram seeds, a bent glass tube, a cork, some lime
                 water, a thistle funnel
                 Procedure
                   •  Take a conical fl ask.

                   •  Put some germina  ng gram seeds in the fl ask.
                   •  Take a bent glass tube and insert its shorter end in
                       a cork through the hole thus fi xing it properly in the
                       conical fl ask.
                   •  Put the longer end of the glass tube in a beaker
                       containing lime water.

                   •  Insert the thistle funnel through the other hole of the
                       cork and fi x it on the fl ask.
                   •  Make the fl ask air   ght and add water into the fl ask through the funnel.
                 Observa  on: You will observe a  er some   me that lime water in the beaker turns milky which shows the
                 presence of carbon dioxide in the conical fl ask.
                 Conclusion: The germina  ng gram seeds in the conical fl ask produce carbon dioxide during respira  on
                 which proves that plants also respire.




                 Combustion or Burning

                 In Ac  vity 5.1, we have seen that the (fi rst two) candles which were covered stopped burning a  er some
                   me. This happened because the supply of oxygen to the candles was cut off . Hence, we conclude that
                 oxygen is necessary for combus  on or burning. Combus  on or burning is a chemical process in which a
                 substance combines with oxygen to produce new substances together with heat and light energy.

                 We generally burn substances in order to obtain heat and light energy. Such substances which are burned
                 to release energy are called fuels.
                       Fuel + Oxygen               Energy (Heat and light) + Carbon dioxide + Water vapour

                 Some commonly used fuels are wood, coal, petrol, diesel, LPG and CNG. Coal and petroleum are commonly
                 known as fossil fuels because they are formed from the remains of plants and animals.



                                                                   Wood
                   Dry wood is widely used as a cooking fuel and to keep warm. It is a cheap and easily available fuel. When dry
                   wood is burned, it releases carbon dioxide and water vapour along with energy.

                                                                    Coal
                   Coal is used as a fuel in power sta  ons, houses, industries and steam engines. It is formed from the dead
                   remains of plants over a long period of   me. It is a form of carbon and when it is burned, it releases a lot of




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