Tuesday, September 18, 2012


Questions 1 to 4 are one mark questions. These are to be answered in one word or one sentence.                                                Section A
1. State the chemical change that takes place when lime stone is heated strongly.
2. .Why do silver articles become black after some time when exposed to air ?
3. Name the device which directly converts solar energy into electrical energy.
4. What are amphoteric oxides ? Choose the amphoteric oxides amongst the following oxides. Na2O, ZnO, Al2O3, CO2, H2O
 Questions 5 to 13 are two marks questions. These are to be answered in about 30 words each.
5. Draw circuit symbols of the following components :  (i) Variable resistance or rheostat
(ii) Plug key or switch (closed)
6. What are antacids ? Name two compounds which are used as antacids.
7. A small amount of ferrous sulphate crystals were heated in a hard glass test tube ? (i) Write the equations involved in the above reaction (ii) Name the type of reaction that takes/ place ?
8. A white salt on heating decomposes to give brown fumes and a residue is left behind. (i) Name the salt. (ii) Write the equation for the decomposition reaction.
9. Out of two solar cookers one was covered by a plane glass slab and the other was left open. Which of two solar cookers will be more efficient and why ?
10. A wire of resistance R is cut into three equal parts. (i) Find the value of resistance of each part in terms of the original resistance R ? (ii) If these three pieces are connected in parallel, what is the ratio of the equivalant resistance so obtained with the original resistance ?
11. How does the strength of the Magnetic field at the centre of a circular coil of a wire depend on : (a) radius of the coil (b) number of turns in the coil
12. State Ohm’s law and write the condition in which this law is obeyed ?
13. (a) What happens when quick lime is added to water ? (b) Write chemical equation for the above reaction. (c) Which type of reaction is this?
Questions 14 to 22  are three marks questions. These are to be answered in about 50 words each
14. Write balanced equations for the reaction of : (a) iron with steam (b) calcium with water.
15. Write the chemical name and formula of washing soda. How is it prepared? Write balanced chemical equation of the reaction.
16. (a) How sodium hydroxide is prepared from sodium chloride ? (b) What will be the pH of the following salts. (i) salt made of strong acid and strong base. (ii) salt made of strong acid and weak base.
17. Determine the ratio of the (a) highest (b) lowest resistance that can be secured by combining four coils of resistance 4 W, 8 W, 12 W, and 24 W in an electric circuit.
18. An electric bulb draws a current of 0.8A from 250 V mains. The bulb is used on an average 8 hours a day, If energy costs Rs 3 per kWh, calculate the monthly bill for 30 days.
19. What is the function of an earth wire ? Why is it to necessary to earth metallic appliances ?
20. (a) Define ‘water of crystallization’. (b) Give two examples of substances having water of crystallization. Write their molecular formulae also.
21. What are exothermic and endothermic reactions. Explain with the help of one example each.
22. In a house, four 60W electric bulbs are lighted for 2 hours and two 100W bulbs are lighted for 4 hours everyday. Calculate the energy consumed in the house for 30 days.
Questions 23 to 25 are five marks questions. These are to be answered in about 70 words each.
23. (i) What causes rusting of iron ? Design an activity to show the conditions needed for iron nails to rust. (ii) Why do we paint iron articles ?
24. (i) Two circular coils P and Q are kept close to each other, of which coil P carries a current. If coil P is moved towards Q, will some current be induced in coil Q ? Give reason for your answer and name the phenomenon involved. (ii) What happens if coil P is moved away from Q ? (iii) State any two methods of inducing current in a coil.
25. (i) With the help of an activity, explain the method of inducing electric current in a coil with a moving magnet. State the rule used to find the direction of electric current thus generated in the coil. (ii) Two circular coils P and Q are kept close to each other, of which coil P carries a current. What will you observe in Q ? (a) If current in the coil P is changed ?
                                                     Section B
 Questions 26 to 41 in section B are multiple choice questions based on practical skills. Each question is a one mark question. You are to select one most appropriate response out of the four provided to you.
(b) If both the coils are moved in the same direction with the same speed ? Give reason.
26.A student tested the pH of distilled water and found that the colour of the pH paper changed to green. He checked the pH again after dissolving a pinch of common salt in it. The colour of the pH paper this time would be :          
(a) Green (b) Yellow (c) Red (d) Blue
27. Two solutions A and B were found to have pH value of 6 and 8 respectively. The inference which can be drawn is :
 (a) The strength of solution B is higher than that of A.      (b) A is an acid while B is base.
(c) both are acidic solutions.                                                   (d) both are basic solutions.
28. Which of the following chemical properties are shown by dilute hydrochloric acid ? (i) It turns blue litmus red (ii) It turns red litmus blue (iii) It reacts with zinc and a gas is evolved (iv) It reacts with solid sodium carbonate to give brisk effervescence
(a) (i) and (ii) only                   (b) (i) and (iii) only
(c) (i), (iii) and (iv) only          (d) (ii), (iii) and (iv) only
29. While doing an experiment a student observed that the blue colour of the aqueous copper
sulpate solution was changed to pale green by immersing a metal rod in it. The metal of the rod
used by the student is :       (a) iron     (b) zinc           (c) silver          (b) aluminium
30. Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that the blue colour of the solution has changed and a layer has deposited on iron filings. Which one of the following set of colours correspond to the colour of the solution and the colour of the coating respectively?
(a) Yellow and green.                          (b) Brown and blue.
(c) Red and greenish blue.                 (d) Light green and reddish brown.
31. A student connects a circuit to study Ohm’s law using a resistor of 3 ohm and a battery eliminator of 6 V. Which of the ammeter should be chosen to read the value of current for this circuit, if the ammeters available in the laboratory have the following ranges? (a) 0 200 m A (b) 0 - 100 mA (c) 0 - 1 A (d) 0 - 2 A
32. Rahul adds aqueous solution of barium chloride to an aqueous solution of sodium sulpate. He would observe that
 (a) a pungent smelling gas is evolved.    (b) the colour of the solution turns red.
(c) a yellow precipitate is formed after sometime.  
(d) a white precipitate is formed almost immediately.
33. The colour of metal deposited when iron nails are dipped in aq. solution of copper sulphate is :  (a) reddish brown (b) no metal is deposited (c) grey (d) silvery white
34. A blue litmus paper was first dipped in dil. HCI and then in dil. NaOH solution. It was observed that the colour of the litmus paper :
(a) Changed to red                               (b) Changed first to red and then to blue
(c) Changed blue to colorless             (d) Remained blue in both the solutions
35. On putting a few drops of a liquid on a pH strip, the colour of the pH strip changed to red. This liquid is most probably :
(a) NaHCO3 (b) HCl (c) NaOH (d) C2H5OH

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