CBSE ADDA

Chapter : IMPROVEMENT IN FOOD RESOURCES BIOLOGY-STUDY NOTES CLASS 9 INTRODUCTION There is a need to introduce production efficiency of crops and livestock because 1. rapid increase in population 2. No major scope of increasing area of land under cultivation. Increase in food production without degrading our environment   and disturbing the ecological balance i.e. Sustainable Practices are required in agriculture and animal   husbandry. TYPES OF CROPS Cereals: wheat, rice, maize, millets and sorghum. Provide carbohydrates for energy requirements. Pulses: pea, gram, black gram, green gram, pigeon pea and lentil. Provide proteins Oilseeds: soya bean, ground nut, sesame, castor, mustard, linseed and sun flower. Provide necessary  fats. Vegetables, spices and fruits provide vitamins and minerals.  Different crop require different climatic conditions, temperature and photoperiods for their growth  and completion of life cycle. Crops which grown in

Q. Find the gram molecular mass of water (H2O) Calculation: 2(H) = 2 x 1 = 2 . 1(O) = 1 x 16 = 16 ∴ Gram molecular mass of H2O= 18g Mole is defined as the amount of substance that contains as many specified elementary particles as the number of atoms in 12g of carbon-12 isotope. One mole is also defined as the amount of substance which contains Avogadro number (6.023 x 10^23) of particles. For eg. one mole of oxygen atoms represents 6.023 x 10^23 atoms of oxygen and 5 moles of oxygen atoms contain 5 x 6 . 0 2 3 x 10 ^23 a t oms of oxygen . Q. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide. [Hint : The mass of an ion is same as that of an atom of the same element. Sol: 1 mole of Al2O3 contains aluminium ions = 2 × 6.022 × 10^23 = 12.044 × 10^23 Now, 102 g of Al2O3 has number of aluminium ions = 12.044 × 10^23 0.051 g of Al2O3 has number of aluminium ions = (12.044 ×1023 × 0.051)/102= 6.022 × 10^20 ions Q. How many atoms of oxygen are present i

Q. Write two differences between isobars and isotopes. Ans:  Isobars           (i) Isobars have the same mass number but different atomic numbers (ii) Isobars have different  chemical properties Isotopes Isotopes have the same atomic number but different mass numbers. Isotopes have similar chemical properties. Q. Why do isotopes shows similar chemical properties. Ans: Due to same number of  electron  in valance shell Q. How Rutherford concluded that the center part of any atom not empty? Ans: When Rutherford experimented with  alpha particles , then he realized that few particles bounced back directly. Rutherford’s result lead him to believe that most of the foil was made of empty space, but had  extremely  small, dense lumps of matter inside, which is present only at the center because from center, few particles bounced back. All other particles deflected at different angles. So Rutherford concluded that the center part of any atom is nucleus not