thnaks to all the members who contribute to this forum. but i request you all ( pls no hard feelings), to answer the questions only in the case when you r cent percent sure and if not then do mention that the answers are doubtful, cos a single mistake commited to answer the questions will most probably be repeated by the students who just consult the forum, and a single mark can put them either side of the margin, pass or fail......so plssssssss be careful.

while going through the EDS papers i felt so good that my brother tabassum shabir awan has contributed alot but in a few answers i have the following information.
dont remeber the year of papers' questions i am mentioning.

1.the brown colour of rust is due to ferric ion in the compund or oxide of ferric oxide. similarly when u cut a fresh apple, its color first is greenish (esp its freshly extracted juice) due to ferrous ion fe++, which is highly reactive with oxygen, thus causing the process of oxidation producing ferric oxide (Fe)2O3, Fe+++.
2. trees shed their leaves in winter because:
it helps the tree to conserve the stored energy in it for hard winters
because leaves are the main source of evaporation, they lower the temperature, causing lowering of the temperature further.
the rate of photosynthesis is much lowered in winters because the intensity of sun's temperature is low, thereby trees dont make use of the leaves' functionality, instead must supply them with the limited food stored, this makes the trees, plants etc to shed their leaves.