1. Question 1 to 10very short answer questions of 1 mark each
4. Question no 23 and 24 are long answer question carrying 5 marks.
1. What is common to all acids?
2. A white chemical compound becomes hard on mixing proper quantity of water. It is also used in surgery to maintain joins in a fixed position. Name the chemical compound.
3. Name a device that help to maintain a potential difference across a conduct
4. A farmer has found that the pH of soil in his fields is 4.2. Name any two chemical material which he can mix the soil to adjust its pH.
5. Write the pH value, after which teeth start decaying?
6. When iron is heated with sulphur, iron sulphide is formed. Name the reaction.
7. Aluminium metal displaces iron from ferric oxide (Fe2O3)giving aluminium oxide and iron. Which is more reactive aluminium or iron?
8. What is the general name of the chemicals which are added to fat and oil containing foods to prevent the development of rancidity.
9. Why is very less quantity of heat energy produced in the connecting wires?
10. Which one has more resistance 100 watt bulb or 60 watt bulb?
11. A solution of a substance ‘X’ is used for white washing:
(i) Name the substances ‘X’ and write its formula. (ii) Write the reaction of he substance ‘X’ named in (i) above with water.
12. Write the balanced chemical equation to represent the following statements:
(i) Carbon (coke) burns in air to form carbon dioxide.
(ii) A piece of sodium metal on putting in water forms caustic soda and hydrogen gas
13. How is the concentration of hydroxide ions (OH-) affected when excess base is dissolved in a solution of sodium hydroxide?
14. A white substance having a strong smell of chlorine is used to clean water in water storage tank. Identify the substance. Write its chemical name and the reaction for its preparation.
15. How is plaster of Paris obtained? What reaction is involved in the setting of a paste of plaster of Paris.
16. Why does a compass needle get deflected when brought near a magnet?
17. Give three points of differences between an electromagnet and a permanent magnet.
18. Write down three precautions that should be taken to avoid the over loading of domestic electric circuits.
19. An electric lamp of 100 W, a toaster of resistance 50 W, and a water filter of resistance 500W are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
20. What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
21 . How can three resistors of resistances 2 W, 3 W, and 6 W be connected to give a total resistance of (i) 4W (ii)1 W?
22. (i) Write the chemical names and formula of bleaching powder.
(ii) Why does bleaching powder smell of chlorine when exposed to air?
(iii) Write chemical equation to represent the action of dilute hydrochloric acid on bleaching powder.
23. (i) What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in atmosphere. (ii) How will you show that the rusting of iron needs oxygen and moisture at the same time?
OR, Write an activity to show that ionic compounds are good conductors of electric current in their aqueous solution.
24. What do you understand by the electrical resistance of a wire? State and define S.I. unit of resistance. The resistance of an electric lamp filament is 230 ohms. The lamp is switched on when the line voltage is 115 volts. What is the current in the lamp circuit? or
(a) What is the difference between direct current and alternating current? (b) Give three points of differences between an electromagnet and a permanent magnet.