CBSE ADDA

Chapter - 8 How Do Organisms Reproduce Points to remember:- Q 1. What is the importance of DNA copying in reproduction? Ans. DNA contains information for inheritance of features from parents to next generation. DNA  present in the cell nucleus is the information source for making proteins. If the information is different,  different proteins will be made. Different proteins will eventually lead to altered body designs. Q 2. Why is variation beneficial to the species but not necessarily for the individual? Ans. Variations are useful for the survival of species in changed environmental situations. For  example, if a population of reproducing organisms were suited to a particular niche (well-defined  place of abode) and if the niche is drastically altered the population could be wiped out. However, if  some variations were to be present in a few individuals in these populations, there would be some  chance for them to survive. Thus if there were a population of bac

10th Our Environment HIGHER ORDER THINKIN SKILLS Chapter - 15 Our Environment HIGHER ORDER THINKIN SKILLS (HOTS) QUESTIONS 1) Write any two ways of energy flow through an ecosystem. 2) Differentiate between biodegradable and non biodegradable with respect to the effect of biological processes on them and the way they affect our environment. 3) Which level shows the maximum biological magnification? Why? 4) Why is a pond self sustaining unit while an aquarium may not be? Justify the answer. 5) Arrange grasshopper, frog, grass, eagle and snake in the form of food chain. 6) If 1000 KJ energy is available at producer level, how much energy will be available at first carnival level? 7) Why do most food chains have 3-5 steps only? 8) Select the biodegradable items from the list given below- Polythene bags, old clothes, wilted flowers, pencil shavings, glass bangles, bronze statue, vegetable peels. 9) What will be impact on ecosystem if bacteria and fungi are removed from the Environment? 10)

X chemistry Carbon and its Compounds Sample guess ... Chapter – 4 Carbon and its Compounds - Points to remember and Important questions paper 1. Carbon forms a large variety of compouds because of its tetravalency and the property of catenation. 2. Hydrocarbons are the compounds of carbon and hydrogen. 3. Hydrocarbons are of two types – saturated hydrocarbons (alkanes) and unsaturated hydrocarbons (alkenes and alkynes) 4. Carbon forms covalent bonds with itself and other elements such as hydrogen, oxygen, sulphur, nitrogen and chlorine. 5. The functional groups such as alcohols, aldehydes, ketones and carboxylic acids bestow characteristic properties to the carbon compounds that contain them. 6. A group / series of hydrocarbons having similar structure and similar properties (i.e. same functional group) is called a homologous series. 7. Carbon chains may be in the form of straight chains, branched chains or rings. 8. Carbon compounds with identical molecular formula but different struc

The modern version of the periodic law is stated as :“ The physical and chemical properties of the elements are the periodic functions of their atomic masses”. LONG FORM OF THE PERIODIC TABLE There are many forms of the periodic tale. The long form of the periodic table is the most convenient and the most widely used and is presented here. The horizontal rows are called PERIODS.  Elements having similar chemical and physical properties appear in vertical columns and are known as GROUPS or FAMILIES. Altogether there are seven periods and 18 groups. PERIODS 1ST Period Contain only 2 elements namely 1H, 2He and is the shortest period. IInd Period Contains 8 elements namely 3Li, 4Be, 5B, 6C, 7N, 8O, 9F and 10Ne is known as the short period. IIIrd Period Contains 8 elements : 11Na, 12Mg, 13Al, 14Si, 15S, 16S, 17Cl, and 18Ar.  The IIIrd period is also known as short period. IV Period starts with potassium and contains 18 elements : 19K, 20Ca, 21Sc, 22Ti, 23V, 24Cr, 25Mn, 26Fe, 2

chemistry adda: 9th chemistry Self-evaluation on Mole concept Sample Problem 1.  Calculate the number of mole in 52 g of Helium. Solution.  We know that, Atomic mass of He = 4u So, its molar mass = 4 g  That is, 4 g of He contains 1 mole of He. Or, 4 g of He = 1 mole of He Or, 1 g of He = 1/4 mole of He So, 52 grams of Helium =1/4 x 52 mole = 13 moles Therefore, there are 13 moles in 52 g of He Sample Problem 2.  Calculate the number of moles for 12.044 X 10 23  atoms of Helium. Solution:  6.022 X 10 23  atoms of Helium           = 1 mole 1 atom of Helium                                 =1/6.022 X 10 23  mole 12.044 X 10 23  atoms of Helium         = [(1/6.022 X 10 23 ) x    12.044 X 10 23   ]moles [ You may use  ----        Number of moles    = (given numbers of particles /Avogadro number)] Sample Problem 3.  How many moles are there in 5 grams of calcium? Sample Problem 4.  How many moles there in 12.044 X 10 23  atoms of phosphorous? Samp

CBSE CHEMISTRY CLASS 9TH CHAPTER - 3 ATOMSAND MOLECULES Download solved paper based on mole concept 9th Mole concept numerical problems solved-CBSE SET- 1 Download File 9th Mole concept numerical problems solved-CBSE SET- 2 Download File practice your learning  1. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g. Molar atomic mass of magnesium is 24g/ mol 2. Verify by calculating that (a) 5 moles of CO 2 and 5 moles of H 2 O do not have the same mass. (b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5. 3. Find the ratio by mass of the combining elements in the following compounds.  (a) CaCO 3 (b) MgCl 2 (c) H2SO4 (d) C2H 5 OH  (e) NH 3   (f) Ca(OH) 2 4. Calcium chloride when dissolved in water dissociates into its ions according to the following equation. CaCl 2 (aq) → Ca 2 + (aq) + 2Cl– (aq) Calculate the number of ions obtained from CaCl 2 when 222 g of it is dissolved in water.

WORK AND ENERGY   9th physics Term-II 1. When a body falls freely towards the earth, then its total energy (a) increases (b) decreases (c) remains constant (d) first increases and then decreases 2. A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car (a) does not change (b) becomes twice to that of initial (c) becomes 4 times that of initial (d) becomes 16 times that of initial 3 . In case of negative work the angle between the force and displacement is (a) 00 (b) 450 (c) 900 (d ) 1800 4 . An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same (a) acceleration (b) momenta (c) potential energy (d) kinetic energy 5 . A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational forc