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Ch.3 PROPERTIES OF NATURAL RESOURCES, EXTRA QUESTIONS, FILL IN THE BLANKS :, 1. The straw fountain works on Bernoulli’s principle., 2. The proportion of water vapour in the air is high during the monsoons and in, coastal areas., 3. In winter, the density of the air increases., 4. Water does not have its own shape but has a volume., 5. When water transforms into solid state, its volume increases., 6. The density of ice is less than that of water., 7. The pH and the electrical conductivity tests, are particularly useful in finding out the, characteristics of soil., ANSWER IN SHORT :, 1) What is called atmospheric pressure?, A) The pressure that is felt on our body due to the molecules in the air is called, atmospheric pressure., 2) True or false : Atmospheric pressure is not the same in all the directions., A) False., 3) In which direction does the air flow?, A) Air flows from a higher pressure area to a lower pressure area., 4) How is the level of humidity of air determined?, A) The level of humidity of air is determined by its capacity to hold water vapour., 5) Give Reason : Air is called a mixture., A) Air contains very fine particles of some gases, dust, smoke and moisture. Hence it is, called a mixture., 6) How does the earth’s surface remain warm?, A) The constituents of air surrounding the earth such as watervapour and carbondioxide, absorb a part of Sun’s heat and give it to the other constituents of air. Thus the earth’s, surface remains warm., 7) True or False : Water expands when the temperature falls below 4 degrees celsius, A) True., 8) When is the World Soil day celebrated?, A) 5th December is celebrated as the World soil day., *****