Education

HOW DO ORGANISMS REPRODUCE(8-10) Question 7: How is the process of pollination different from fertilization? Answer:  Pollination is the process of transfer of pollens from anther to stigma. It occurs with the help of certain pollinators such as air, water, birds, or some insects. Fertilization, on the other hand, is the fusion of the male and female gametes. It occurs inside the ovule and leads to the formation of zygote. Question 8: What is the role of the seminal vesicles and the prostate gland? Answer:  The secretions from seminal vesicles and prostate glands lubricate the sperms and provide a fluid medium for easy transport of sperms. Their secretion also provides nutrient in the form of fructose, calcium, and some enzymes. Question 9: What are the changes seen in girls at the time of puberty? Answer:  Secondary sexual characteristics in girls: Increase in breast size and darkening of skin of the nipples present at the tips of the breasts. Appearance of hair in the geni

HOW DO ORGANISMS REPRODUCE(11-16) Question 11: If a woman is using a copper−T, will it help in protecting her from sexually transmitted diseases? Answer:  No. Using a copper-T will not provide a protection from sexually transmitted diseases, as it does not prevent the entry of semen. It only prevents the implantation of the embryo in the uterus. Question 12: Asexual reproduction takes place through budding in (a) amoeba. (b) yeast. (c) plasmodium. (d) leishmania. Answer:  (b) Asexual reproduction takes place through budding in yeast. Question 13: Which of the following is not a part of the female reproductive system in human beings? (a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube Answer:  (c) Vas deferens is not a part of the female reproductive system in human beings. Question 14: The anther contains (a) sepals. (b) ovules. (c) carpel. (d) pollen grains. Answer:  (d) The anther contains pollen grains. Question 15: What are the advantages of sexual reproduction ove

HOW DO ORGANISMS REPRODUCE(17-21) Question 17: Why does menstruation occur? Answer:  Menstruation is a process in which blood and mucous flows out every month through the vagina. This process occurs every month because one egg is released from the ovary every month and at the same time, the uterus (womb) prepares itself to receive the fertilized egg. Thus, the inner lining of the uterus gets thickened and is supplied with blood to nourish the embryo. If the egg does not get fertilised, then the lining of the uterus breaks down slowly and gets released in the form of blood and mucous from the vagina. Question 18: What are the different methods of contraception? Answer:  The contraceptive methods can be broadly divided into the following types: Natural method→ It involves avoiding the chances of meeting of sperms and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore, the c

HOW DO ORGANISMS REPRODUCE(1-6) Question 1: Why is variation beneficial to the species but not necessarily for the individual? Answer: Variations are beneficial to the species than individual because sometimes for a species, the environmental conditions change so drastically that their survival becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire species of bacteria would have been destroyed. Thus, these variants help in the survival of the species. However, all variations are not necessarily beneficial for the individual organisms. – Question 2: How does binary fission differ from multiple fission? Answer: In binary fission, a single celldivides into two equal halves. Amoeba and Bacteria divide by binary fission. Question 3: How will an organism be benefited i

PERIODIC CLASSIFICATION OF ELEMENTS(27-32) Question-27 Name four alkaline earth metals. To which group do they belong? Solution: The four alkaline earth metals are beryllium, magnesium, calcium and strontium. They belong to II A group. Question-28 What is called diagonal relationship? Solution: The similarity in properties between certain elements of different periods placed diagonally to one another in a periodic table is called diagonal relationship. Question-29 Define electron affinity. Solution: It is defined as the amount of energy released in adding an extra electron to an isolated neutral gaseous atom in its lowest energy state, to convert it into gaseous ion. Electron affinity increases as one moves from left to right in periods or top to bottom in groups. Question-30 What is called electronegativity? Solution: The property of atoms to attract electrons in a covalent bond is called electronegativity. (i) In periods, electronegativity increases with the increas

PERIODIC CLASSIFICATION OF ELEMENTS(20-26) Question 20: How does the electronic configuration of an atom relate to its position in the Modern Periodic Table? Answer:  In the modern periodic table, atoms with similar electronic configurations are placed in the same column. In a group, the number of valence electrons remains the same. Elements across a period show an increase in the number of valence electrons. Question 21: In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium? Answer:  The element with atomic number 12 has same chemical properties as that of calcium. This is because both of them have same number of valence electrons (2). Question-22 What are the merits and demerits of newland’s classification? Solution: Merits (i) This classification worked well for lighter elements only up to Ca. (ii) This classificat

PERIODIC CLASSIFICATION OF ELEMENTS(14-19) Question 14: Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as Answer:  (b) X would most likely be in the same group of the Periodic Table as magnesium (Mg). Question 15: Which element has (a) two shells, both of which are completely filled with electrons? (b) the electronic configuration 2, 8, 2? (c) a total of three shells, with four electrons in its valence shell? (d) a total of two shells, with three electrons in its valence shell? (e) twice as many electrons in its second shell as in its first shell? Answer:  (a) Neon has two shells, both of which are completely filled with electrons (2 electrons in K shell and 8 electrons in L shell). (b) Magnesium has the electronic configuration 2, 8, 2. (c) Silicon has a total of three shells, with four electrons in its valence shell (2 electrons in K shell, 8 e

 PERIODIC CLASSIFICATION OF ELEMENTS(8-13) Question 8: Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice? Answer: Calcium (Ca) and strontium (Sr) are expected to show chemical reactions similar to magnesium (Mg). This is because the number of valence electrons (2) is same in all these three elements. And since chemical properties are due to valence electrons, they show same chemical reactions. Question 9: Name (a) three elements that have a single electron in their outermost shells. (b) two elements that have two electrons in their outermost shells. (c) three elements with filled outermost shells. Answer: (a) Lithium (Li), sodium (Na), and potassium (K) have a single electron in their outermost shells. (b) Magnesium (Mg) and calcium (Ca) have two electrons in their outermost shells. (c) Neon (Ne), argon (Ar), and xenon (Xe) have filled outermost shells. Question 10: (a) Lithiu

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Complementary Angles In a right triangle,sum of two angles other than a right angle is complementary,so if we take that complementary angles as A and B,then,A=90-B or B=90-A,so we can write,        sin(90-A)=cosA,        cos (90-A) =sinA,        tan (90-A) =cotA,        cot (90-A) =tanA,        cosec (90-A) =secA,        sec (90-A) =cosecA, and same thing you can do for angle B too.

Trigonometric Angles Trigonometric angles are very easy to learn if u follow some of these steps- From the table ,just learn the values of sin θ  upto 90 and now see that as now move from left to write in sin θ ,the same values will come when you move from right to left in cos θ .Now the next column is of tan θ ,we know that tan θ =sin θ /cos θ ,so we can easy calculate by dividing sin θ  and cos θ .Then next we move on to cot θ ,which can be find out by doing inverse of tan θ  or by dividing cos θ  and sin θ ,as cot θ =1/tan θ  or cot θ =cos θ /sin θ .now go to sec θ ,it is reciprocal of cos θ ,cos θ =1/cos θ ,and at the end it is cosec θ ,which can be find out by finding reciprocal of sin's value,as cosec θ =1/sin θ . Angles can be c omplementary angles and complex angles

Trignometric Ratios These are used to compare the two sides,from the three that the triangle have.The side opposite to right angle is called hypotenuse(H),the side opposite to the known angle is said as perpendicular(P) and the third side is called base(B) and  θ  be an angle. The comparison between hypotenuse and perpendicular is shown by two functions-         sin θ =P/H         cosec θ =H/P The comparison between hypotenuse and base is shown by two functions-         cos θ =B/H         sec θ =H/B The comparison between  perpendicular   and base is shown by two functions-         tan θ =P/B         cot θ =B/P

Introduction to  Trigonometry Trigonometry is greek word,which mean to measure the sides and angles of a triangle.If we know one of the angle of a triangle and one of its side,it is easy to calculate the other sides and other angles... We can divide trigonometry in following parts for better understanding of the topic. Trigonometric Ratios Trigonometric Angles - Complementary Angles Complex Angles Trigonometric Identities or Pythogorean Identities Angle Transformation Formulae Common Formulae

शहीद- ए   म र्त्यर्  राष्ट्र का कोई पिता नहीं होता , राष्ट्र के तो सपूत होते हैं, फिर क्यों  गांधी राष्ट्रपिता, और भगत सिंह आतंकवादी कहलाया.... अच्छा हुआ भगत सिंह तेरा फोटो न आया नोटों पर, वरना कुचला जाता शीला मुन्नी के कोठों पर, तू लोगों के दिल में रहेगा, गांधी को रहने दे होठों पर, तू तो शहीद हुआ, ना जाने कैसे तेरी माँ सोई होगी....? एक बात तो तय है, तुझे गले लगाकर, रस्सी भी सौ बार रोई होगी....    जय हिन्द जय भारत 

SHAHEED - A MARTYR RASHTRA KA KOI PITA NAHI HOTA, RASHTRA KE TO SAPUT HOTE HAIN, FIR KYUN GANDHI RASHTRAPITA, AUR BHAGAT SINGH ATANKVAADI KEHLAAYA... ACCHA HUA BHAGAT SINGH TERA PHOTO NA AYAA NOTO PE, VARNA KUCHLA JAATA MUNNI SHEELA KE KOTHO PE, TU LOGO KE DIL ME RAHEGA, GANDHI KO REHNE DE HOTHON PE, TU SHAHEED HUA, NAA JAANE KAISE TERI MAA SOI HOGI..?? EK BAAT TO TAYE HAI, TUJHE GALE LAGAAKR,  RASSI BHI SAU BAAR ROYI HOGI...

     CARBON AND ITS COMPOUND(10-17)  Question 10: Explain the formation of scum when hard water is treated with soap. Answer: Soap does not work properly when the water is hard. A soap is a sodium or potassium salt of long chain fatty acids. Hard water contains salts of calcium and magnesium. When soap is added to hard water, calcium and magnesium ions present in water displace sodium or potassium ions from the soap molecules forming an insoluble substance called scum. A lot of soap is wasted in the process. Question 11 : What change will you observe if you test soap with litmus paper (red and blue)? Answer: Since soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue. Question 12: What is hydrogenation? What is its industrial application? Answer: Hydrogenation is the process of addition of hydrogen. Unsaturated hydrocarbons are added with hydrogen in the presence of palladium and nickel catalysts to give saturated hy

            PERIODIC CLASSIFICATION OF ELEMENTS(1-7) Question 1: What were the limitations of Dobereiner’s classification? Answer: Limitation of Dobereiner’s classification: All known elements could not be classified into groups of triads on the basis of their properties. Question 2: What were the limitations of Newlands’ Law of Octaves? Answer: Limitations of Newlands’ law of octaves: (i) It was not applicable throughout the arrangements. It was applicable up to calcium only. The properties of the elements listed after calcium showed no resemblance to the properties of the elements above them. (ii) Those elements that were discovered after Newlands’ octaves did not follow the law of octaves. (iii) The position of cobalt and nickel in the group of the elements (F, Cl) of different properties could not be explained. (iv) Placing of iron far away from cobalt and nickel, which have similar properties as iron, could also not be explained. Question 3: Use Mendeleev’s Period

         CARBON AND ITS COMPOUND(6-9) Question-6 A hydrocarbon molecule contains 4 hydrogen atoms. Give its molecular formula, if it is an: (i) alkane, (ii) alkene (iii) alkyne. Solution: (i) An alkane containing 4 hydrogen atoms in its molecule is methane, CH 4 . (ii) An alkene containing 4 hydrogen atoms in its molecule is ethane, C 2 H 4 (iii) An alkyne containing 4 hydrogen atoms in its molecule is propyne, C 3 H 4. Question-7    Why common salt is added in soap making? Solution: Common salt is added to the mixture to make the soap come out of solution. Though most of the soap separates out on its own but some of it remains in solution. Common salt is added to precipitate out all the soap from the aqueous solution. Actually, when we add common salt to the solution, then the solubility of soap present in it decreases, due to which all the soap separates out from the solution in the form of a solid. Question-8   What is meant by denatured alcohol? What is the need t