CBSE ADDA

Corrosion  is defined as the slow and steady destruction of a metal by the environment. It results in the deterioration of the metal to form metal compounds by means of chemical reactions with the environment. Rusting of iron  requires air and water.Iron articles are shiny when new, but get coated with a reddish brown powder called rust(Fe2O3.nH2O) when left for some time. This process is commonly known as rusting of iron. The black coating on silver and the green coating on copper are other examples of corrosion Read more 

Study Material : Education Meaning Purpose Philosophy What is Education? Education is a continuing voyage of discovery, an everlasting quest to achieve the fullest wisdom and stature that God meant for us. The word education comes from the Latin educare, to draw out. In a broad sense it means not only to elicit creative thought and knowledge from the student, but to draw  humankind out of the predicament it is in. What are the Purpose of Education? To restore in man the image of his Maker, to bring him back to the perfection in which he was created, to promote the development of body, mind, and soul, that the divine purpose in his creation might be realized–this was to be the work of redemption. This is the object of education, the great object of life. Education enables humans to achieve their fullest personal, spiritual, mental, social, and physical potentials. The ability of being educated is what dis

FOOD: Where does it come from. 1. You are the manager of a restaurant, make a list of food items you would serve in lunch. 2. What measures are to be taken to avoid wastage of food. 3. Why are humans considered omnivores? 4. List the ingredients of any five food items you relish. 5. Form pairs of words in group A with words in group B. A—Mustard plant, Nectar, Beetroot, carnivore, omnivore. B-- Honey, sugar, oil, humans, tiger. 6. Name two aquatic plants eaten as food. COMPONENTS OF FOOD 1. Why is it necessary to have fresh and un-cooked vegetables and fruits in our diets. 2. Doctors advice us to drink atleast two litres of water daily why? 3. What happens when wheat flour is sieved before making dough? 4. It is not good to wash vegetables and fruits after cutting, why? 5. Rice and pulses must not be washed repeatedly , why? 6. Prove that, milk you drink contains proteins. 7. How will you check whether rice contains starch.

Source :  http://chemistryadda.blogspot.com Q.1. Why is sodium kept immersed in kerosene oil? Q.2. Name two metals which are found in nature in the free state. Q.3. What chemical process is used for obtaining a metalfrom its oxide. Q.4. Which metals do not corrode easily? Q.5. Why copper is used to make hot water tanks and not steel . Q.6. What is an alloy? Name the constituents of 22-carat gold. Why is 24-carat gold converted to 22-carat gold? Q.7. Why are metals good conductors of electricity? Q.8 Give reasons for the following: (a) Zinc oxide is considered as amphoteric oxide. (b) Non-metals in general do not displace hydrogen from dilute acids. (c) Metals conduct electricity.

Section -A 1.The pair of equations x + 2 y + 5 = 0 and –3 x – 6 y + 1 = 0 have (A) a unique solution (B) exactly two solutions        (C) infinitely many solutions (D) no solution 2. If a pair of linear equations is consistent, then the lines will be (A) parallel      (B) always coincident             (C) intersecting or coincident             (D) always intersecting 3. The pair of equations y = 0 and y = –7 has (A) one solution          (B) two solutions        (C) infinitely many solutions              (D) no solution 4.If sinA + sin2A = 1, then the value of the expression (cos2A + cos4A) is (A) 1                                        (B)1/2                          (C) 2                                                   (D) 3 5. Given that sinα =1/2 and cosβ =1/2 , then the value of (α + β) is (A) 0°              (B) 30°                                    (C) 60°                                                            (D) 90° Section - B 1.For which values of p and q , will

1: A metal is found in liquid state in nature .It is less reactive than hydrogen .It occurs as sulphide ore .Describe the reactions how can we extract this metal from its ore .Name the ore also. 2: Explain why (i) Aluminium cannot be extracted by reducing alumina with carbon. (ii)Concentrated HNO 3 can be stored in aluminum containers. (iii)Aluminium is used for making transmission wires. (iii) 24 carat gold cannot be used for making ornaments. 3: An alkali metal A gives a compound B (molecular mass=40) on reacting with water .The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B, and C and give the reaction involved. 4: A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen. 5: Given below are the steps for extraction of copper from its ore .Write the reaction involved (i)Roasting of copper (I) sulphide.

1. Explain why the surface of some metals acquire dull appearance when exposed to air for a long time. (2 marks) 2. What are amphoteric oxides? Give examples two amphoteric oxides. (2 marks) 3. State two ways to prevent the rusting of iron. (2 marks) 4. Why is aluminum extracted from alumina by electrolytic reduction and not by reducing with carbon? (2 marks) 5. The reaction of a metal X with Fe2O3 is highly exothermic and is used to join broken railway tracks. Identify metal X. Write the chemical equation of its reaction with Fe2O3. (2 marks) 6. Metal sulphides occurs mainly in rocks and the metal halides occur mostly in seas and lakes. What could be the reason for this difference in behavior? (2 marks)