1. What is the percentage of water in human body? 65%
2. What is the chemical name of water? dihydrogen monoxide (H2O).
3. The process of breaking down of water molecules by the passage of electric current is known as electrolysis of water.
4. What is the ratio of hydrogen and oxygen in water ? 2:1.
5. Water is produced by the reduction of metal oxide by hydrogen, burning of hydrogen in air and burning of hydrocarbons in air.
6. Who discovered hydrogen ? Henry Cavendish.
7. Who produced water artificially and in which year ? Henry Cavendish, in 1781.
8. Who called Hydrogen as inflammable air? Henry Cavendish.
9. Who mixed metals with strong acids and created hydrogen.? Henry Cavendish.
10. Who created carbon dioxide also by combining metals with strong bases? Henry Cavendish.
11. Pure water boils at 100° C at one atmospheric pressure.
12. Pure water freezes at exactly 0°C at one atmospheric pressure.
13. Pure water has a density of 1 gm/cm3.
14. What is the reason behind pressure cooker takes less time to cook ? The boiling point of water increases with increase in pressure.
15. The freezing point of water decreases with increase in pressure.
16. Density of water at different temperature. Match the following.
17. 1CC = 1 cm3 = 1mL
18. For the same mass of ice and of water, the volume of ice is more than that of water.
19. What is the latent heat of fusion of ice? 80 calories/g. or 336 J/g.
20. The freshness of fish and meat can be maintained by placing them in contact with ice why ? Latent heat of fusion of ice is high.
21. What is the value of latent heat of vaporization of water? 540 calories/g or 2268 J/g.
22. Why water is used to cooling engines? The specific heat capacity of water is very high.
23. Which liquid has highest specific heat capacity? Water.
24. What is the specific hear capacity of water ? One gram of water requires 1 calorie of heat to raise its temperature by 1°C.
25. If water is heated to 200°C, 0.02% of water decomposes to form hydrogen and oxygen gas.
26. Copper does not react with water at any temperature.
27. Red hot carbon (coke) reacts with steam to produce water gas (Carbon monoxide + H2).
28. Chlorine gas dissolves in water and produces hydrochloric acid.
29. Water - A Universal Solvent.
30. Why concentric rings are not formed in the rain water and distilled water after evaporation? They do not contain dissolved solids.
31. Air dissolved in water contains approximately 35.6% oxygen along with nitrogen and carbon dioxide.
32. Carbon dioxide dissolved in water reacts with limestone to form calcium bicarbonate.
33. Marine organisms such as snails, oysters, etc., extract calcium carbonate from calcium bicarbonate to build their shells.
34. Every litre of potable water contains 1- 2 grams of dissolved salts, mainly common salt.
35. Every litre of sea water contains 35 grams of dissolved salts most commonly known as sodium chloride (NaCl).
36. In addition to the common salt, there are small amounts of calcium (Ca), magnesium (Mg), potassium (K), copper (Cu) and zinc (Zn).
37. The minerals in water give it a certain taste.
38. Out of the total fresh water available on the earth, only 1% is present in water bodies such as rivers and lakes.
39. Every year 4.6 million children die due to diarrhea.
40. The chemicals that are used in this process of sterlisation of water are chlorine and ozone.
41. RO stands for the name of the technology, ‘reverse osmosis’, used in these purifiers.
42. Some RO purifiers also have a UV (ultraviolet) rays junit that destroys the germs present in water.
43. Hardness of water is due to the presence of dissolved salts of calcium and magnesium.
44. Temporary hardness of water is due to the presence of carbonate and bicarbonate salts of calcium and magnesium.
45. permanent hardness results due to the presence of chloride and sulphate salts of calcium and magnesium.
46. Temporary hardness is easily removed from water by boiling. When heated, the calcium hydrogen carbonate decomposes producing insoluble calcium carbonate.
47. Washing soda is used to remove permanent hardness of water. Adding washing soda converts chlorides and sulphates into insoluble carbonates.
48. What are the methods are there to remove hardness of water? Boiling, Adding washing soda,
Ion – exchange, Distillation.
49. The pleasant taste of drinking water is due to the presence of dissolved substances which include air, carbon dioxide and minerals.
50. There are 17 major river basins in Tamil Nadu with 61 reservoirs.
51. About 90% of the available surface water has already been tapped mainly for agriculture and irrigation.
52. The largest source of water pollution in India is untreated sewage. On an average, a person uses 135 litres of water per day for washing clothes, cooking, bathing, etc.
53. Excess of nutrients such as nitrates and phosphates as well as toxic chemicals in water bodies. It is called Eutrophication.
56. Solubility of carbon dioxide in water is high when the
a) pressure is low b) pressure is high c) temperature is high d) None of the above
57. The gas collected at the cathode on electrolysis of water is
a) oxygen b) hydrogen c) nitrogen d) carbon dioxide
58. Which of the following is a water pollutant?
a) Lead b) Alum c) Oxygen d) Chlorine
59. Permanent hardness of water is due to the presence of __________
a) sulphates and chlorides b) dust particles
c) carbonates and bicarbonates d) other soluble particles
60. Water is colourless, odourless and tasteless
61. The boiling point of water is 100oc
62. Temporary hardness of water can be removed by boiling of water.
63. The density of water is maximum at lowest temperature
64. Loading speeds up the process of __________
III. State true or false. If false, correct the statement.
65. Sewage should be treated well before being discharged it into water bodies. True
66. Sea water is suitable for irrigation as it contains dissolved salts. False, not suitable for irrigation.
67. Excessive use of chemical fertilizers depletes the soil and causes water pollution. True
68. The density of water will not change at all temperature? False, It will change over temperature.
69. Soap lathers well in hard water. False, It will not laters.
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