Page 114 - ICSE Chemistry 6
P. 114

Air pollu  on:        The release of harmful par  cles and gases into the air that have damaging eff ects on
                                       living things and the environment
                 Air pollutants:       Gases and par  cles in the atmosphere that harm organisms and aff ect climate
                 Greenhouse gases:     Gases such as methane, carbon dioxide and water vapour that trap heat energy of the
                                       sun
                 Greenhouse eff ect:    The trapping of heat energy of the sun by greenhouse gases present in the earth's
                                       atmosphere
                 Global warming:       The increase in the average temperature of the earth's atmosphere, especially a
                                       sustained increase which is great enough to cause changes in the global climate
                 Acid rain:            Rain containing harmful chemicals from gases like nitrogen oxides and sulphur oxides
                                       that damages trees, crops, animals and buildings



                      Quick Review

                    •  Air is present everywhere around us.
                    •  The presence of atmosphere makes life possible on the earth.
                    •  Atmosphere is the layer of air that surrounds the earth.
                    •  Air is a mixture of gases. Air is made up of nearly 78% nitrogen, 21% oxygen, 0.9% argon, 0.04%
                       water vapour, 0.03% carbon dioxide and the remaining 0.03% are the other trace gases.
                    •  Air also contains suspended dust par  cles and smoke.
                    •  Nitrogen does not support combus  on. It is needed by plants to grow.
                    •  The presence of oxygen is essen  al for survival of living organisms. It is also required for combus  on.
                    •  Carbon dioxide is also important for sustenance of life. Plants need carbon dioxide for
                       photosynthesis. Human beings and animals take in oxygen from the atmosphere and release carbon
                       dioxide during breathing. The concentra  on of carbon dioxide in the atmosphere aff ects the global
                       temperature.
                    •  Water vapour are also present in the atmosphere. They are formed due to evapora  on and boiling of
                       water.
                    •  Air also contains suspended dust par  cles and smoke.
                    •  The balance between the levels of oxygen and carbon dioxide in the atmosphere is maintained by
                       two processes—respira  on and photosynthesis.
                    •  Air pollu  on can be harmful for our survival. We must take adequate steps to control it.




                                                              EXERCISES



                 BE PROMPT

                 A.  Fill in the blanks.

                       1.  Air exerts equal ___________ in all direc  ons.
                       2.  All animals and plants need ____________ for respira  on.
                       3.  Solid carbon dioxide is called _____________.


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