Chapter 1: Natural Resources: Air, Water and Land 1. Natural Resources : Air, Water and Land. Let s Revise

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1 z Chapter 1: Natural Resources: Air, Water and Land 1. Natural Resources : Air, Water and Land Let s Revise 1. Natural Resources: i. The elements available in the nature that fulfill the basic needs of living things on earth, thereby allowing life to sustain on earth are known as Natural Resources. ii. Air, water and land are called the earth s atmosphere, hydrosphere and lithosphere iii. respectively. Living things and the parts of the lithosphere, hydrosphere and atmosphere which they occupy are together called as biosphere (In Greek, bios = life, sphaira = sphere). 2. Air: i. Air in the atmosphere around the earth comprises of various gases such as nitrogen, oxygen, carbon dioxide, six inert gases, nitrogen dioxide, sulphur dioxide, water vapour and dust particles. ii. iii. Proportion of gases in air is as follows: Spheres of Earth Proportion of gases Troposphere 80% of the total mass of gases in the air Stratosphere 19% of the total mass of gases in the air Mesophere and Ionosphere Proportion of gas goes on decreasing Exosphere Lacks gases completely Uses of the different gases in air are as follows: Gas Nitrogen Oxygen Carbon dioxide Argon Helium Neon Krypton Xenon Uses Helps living things to build necessary proteins. Useful in production of ammonia also, in food industry for air tight packaging of food items. Essential for respiration (breathing in living things) and for burning (combustion). For photosynthesis (in plant) and is a major constituent of fire extinguishers. Used in electric bulbs. Used for obtaining low temperature and for generating lift in airships. Used in street lights and decorative lights. Component of fluorescent tubes. Used in flash photography. iv. Atmosphere acts as an important filter, because: a. It allows light and heat to reach earth s surface in quantities required for life to sustain on earth. b. Also, it prevents harmful elements from reaching the earth. v. Fog, clouds, snow and rain are produced in atmosphere. vi. Air pollution: Any undesirable change in the normal composition of the air by addition of harmful gases is known as air pollution. 1

2 Std. VI: General Science Workbook 2 vii. Air pollution is caused by harmful gases given out through combustion of fuels in vehicles and in big industries. It is also caused due to incomplete combustion of fuels like coal and wood. viii. Nitrogen dioxide, carbon dioxide, carbon monoxide, sulphur dioxide and soot are some harmful air pollutants. 3. Ozone layer: i. Ozone layer is present in the lower part of the stratosphere. ii. It functions as a shell to protect the earth from harmful ultra violet rays coming from the sun. iii. Chemical gases like Carbon tetrachloride, Chlorofluorocarbons used in air conditioners and refrigerators mix with air and destroy ozone layer. 4. Water: i. It is said that Water is life, because it is absolutely essential for survival of living things. ii. Water is colourless, tasteless and odourless. It is universal solvent (many substances readily dissolves). It occurs in three states such as solid (ice), liquid (water) and gaseous (water vapour). iii. The blood of animals and sap in plants contain a very high proportion of water. iv. Water available on earth: a. Water in seas and oceans: 97% b. Ground water, frozen state (ice): 2.7% c. Fresh, drinking water: 0.3% Thus, only 0.3% of total water covering the earth s surface can be utilized for the purpose of drinking. 5. Water cycle: i. Water cycle that leads to rainfall is the major source of water on earth. ii. Water evaporates from the oceans, gets stored in the clouds and condenses as rain. Thus, fresh water enters the ocean, thereby completing the cycle. iii. Rain water also seeps into the ground, thereby increasing the ground water level. iv. This gives rise to other sources of water like rivers, ponds, springs, lakes, streams. Uncontrolled use of water for the ever increasing population, industry and farming has resulted in shortage of water. v. Thus, it is necessary to use water sparingly. Water can be percolated in the ground by blocking it. Stored water does not become stale at once, thus it can be reused wherever possible. 6. Land: i. Land is seen in the form of stones, soil, big rocks. ii. Both plants and animals need land. Humans live on land as well as utilize it for other purposes like shelter, farming etc. Land is an important source of minerals, crude oil and natural gas, which are useful for humans in many ways. Layers of land: a. Humus: Topmost mature layer. It is most fertile layer formed by decomposition of animals and plants. Layers of land Humus Top soil Immature soil Layer of soil and small rocks Bedrock

3 z Chapter 1: Natural Resources: Air, Water and Land iii. iv. b. Top soil: Full of sand, soil, small stones, worms and insects. c. Immature soil: Comprises of soil and pieces of bedrock. d. Bed rock: A layer with less soil and more rocks. Minerals are obtained from this layer. Responsible for colour and texture of the soil. Soil formation is slow, continuous and natural process. It takes about a Wind Cold thousand years for a 2.5 cm thick layer of mature soil to form. Heat, cold and water breakdown the bedrocks into pieces. From these pieces stones, sand and soil particles are formed. v. Microbes, worms and insects as well as rodents like mice and rats are found here. Roots of trees also contribute in weathering of rocks. vi. Soil erosion occurs due to natural calamities like earthquakes, fluids, storms and human activities such as mining, farming and deforestation etc. It makes land barren. vii. Thus, to prevent soil erosion, it is necessary to plant more trees, as the roots of trees/plants/ grasses and bushes hold the soil particles tightly. viii. Formation of fossil fuels: Geographical upheavals led to burial of the trees and animals deep inside the land. Burial of the remains of plants and animals for many ages led to formation of fossil fuels. ix. Fossil fuel gives us many useful substances such as petrol, diesel, kerosene, paraffin, tar and wax. x. All living things utilize the natural resources for their survival but the availability of natural resources in the environment is limited. For example Oxygen 21% Fresh water 0.3% Land 29% Thus, one need to use these resources judiciously. xi. Heat Microbes Rodents India Meteorological Department (IMD) was established in 1875 for studying the weather in Indian subcontinent. Summative Assessment Rock Stones, Sand, Soil Formation of layer of soil Breaks down into Water Roots of plants Fill in the blanks *1. The layer of ozone gas absorbs rays that come from the sun to the earth. *2. Of the total water available on the earth, fresh water forms percent. *3. Both and constituents are present in the soil. 3

4 Std. VI: General Science Workbook 4. Atmosphere, hydrosphere and lithosphere constitute the Gases are absent in layer of atmosphere. 6. Fog, snow and rain are formed in Right or Wrong? If Wrong, write the correct sentence *1. Land and soil are the same thing. *2. The water in a lake is called ground water. *3. It takes about 1000 years to form a 25 cm thick layer of soil. *4. Radon is used in decorative lights. 5. Weathering of rock is the initial process of soil formation. 6. Hydrosphere occupies 71% of the earth s surface. 7. The land on the earth s surface is the lithosphere. 8. Soil is formed by man-made process. Odd one out 1. Soot, nitrogen dioxide, carbon monoxide, oxygen, sulphur dioxide. 2. Petrol, paraffin, diesel, kerosene, chlorofluorocarbon. 4

5 z Match the Following Chapter 1: Natural Resources: Air, Water and Land *1. Match the natural resources from Group A with the related descriptions given in Group B. Group A Answer Group B i. Carbon dioxide a. Generation of soil ii. Oxygen b. Rain iii. Water vapour c. iv. Microbes d. Combustion Plants and food production 2. Match the name of the gases from Group A with their uses given in Group B. Group A Answer Group B i. Xenon a. ii. Argon b. Used to obtain low temperature Used in fire extinguishers iii. Helium c. Used in electric bulbs iv. Carbon dioxide d. Useful in agriculture Answer in one word 1. Name the following *i. Constituents of the biosphere *ii. Biotic constituents of soil *iii. Fossil fuel *iv. Inert gases in air *v. Gases that are harmful to the ozone layer vi. The topmost fertile natural layer of the soil vii. The process of destruction of fertile layer of soil by floods, storm and human activities viii. The institute established for studying the weather changes and making the forecasts about rainfall in the Indian subcontinent

6 Std. VI: General Science Workbook Answer in your own words *1. Explain with the help of a diagram how soil is formed. Ans: *2. Why is there a shortage of water even though it occupies about 71% of the earth s surface? 6

7 z *3. What are the various constituents of air? Write their uses. Chapter 1: Natural Resources: Air, Water and Land *4. Why are air, water and land considered to be valuable natural resources? 7

8 Std. VI: General Science Workbook 5. Can you tell? (Textbook pg. no. 5) i. What is land made of? Ans: ii. Is land flat every where? 8

9 z iii. Does man produce soil / land? Chapter 1: Natural Resources: Air, Water and Land iv. If a deep pit is dug in the ground, what do you find there? Give reasons 1. Why is it said that? *i. The ozone layer is a protective shell of the earth. *ii. Water is life. *iii. Seawater is useful even though it is not potable. 9

10 Std. VI: General Science Workbook iv. Atmosphere is an important filter. Answer the following 1. What will happen if: *i. Microbes in the soil get destroyed. *ii. The number of vehicles and factories in your surroundings increases. *iii. The total supply of potable water is finished. 10

11 z Open ended questions Chapter 1: Natural Resources: Air, Water and Land 1. Why is it said that individuals suffering from high blood pressure and asthma are advised not to visit hill stations? 2. What will happen if: i. All the trees on the earth are cut. ii. Resources are not used judiciously. 3. Use your brain power! (Textbook pg. no. 3) What would have happened if there were no air on the earth? 11

12 Std. VI: General Science Workbook 1. Which day is celebrated as Ozone Protection Day? 2. How much water do we need to drink per day for normal functioning of our day? 3. What is the proportion of humus is the layer of good fertile soil? 4. Tell any two uses of carbon dioxide. Apply your knowledge Oral Test Formative Assessment 1. Observe (Textbook pg. no. 1) Observe the figure given above and answer the following questions: i. Where do we see the birds? Ans: ii. Where is the cow grazing? Ans: - iii. Locate the trees and the road. Ans: iv. Where does the river come from? How does it flow? Ans: v. Where is the aeroplane? Spheres of the earth vi. Where are the fish seen? vii. On what is the sail boat floating? 2. Can you recall? (Textbook pg. no. 2) What are the five layers of the atmosphere? 12

13 z 3. Observe (Textbook pg. no. 3) Chapter 1: Natural Resources: Air, Water and Land Air pollution Observe the figure given above. What is the similarity in the three pictures? 5. Lets try this (Textbook pg. no. 4) Observe how much water is used and for what purposes it is used in your house for a whole day. Record it in a chart like the one shown below. Discuss this data in the class. Divide the total amount of water used in your house by the number of persons to find out how much water each person needs. Purpose for which water is used Amount of water (approx. in litres) Bath Brushing teeth Washing clothes and utensils Mopping the floor Drinking Cooking Total use of water 6. Find out (Textbook pg. no. 4) In what ways is the water in sea and oceans useful even though it is salty? 13

14 Std. VI: General Science Workbook 7. Observe (Textbook pg. no. 5) Observe the figure given above and answer the following questions. i. For which purposes is water being used? Ans: Uses of water on the earth ii. Do other living things use water like we do? 8. Can you tell? (Textbook pg. no. 5) i. What do you see on land? 14

15 z Chapter 1: Natural Resources: Air, Water and Land ii. What has man created on land? 9. Use your brain power! (Textbook pg. no. 7) What are the constituents of soil? Classify them as biotic and abiotic constituents. Activity/Project 1. Lets try this (Textbook pg. no. 6) Perform the following activity Take a transparent plastic bottle, a handful of soil, some stones, sand, some dry leaves and water. Cut off the upper tapering part of the bottle. Put the rest of the materials in the lower part and add water. Stir the mixture thoroughly and put it aside. Observe it the next day and answer the following questions. i. How does the mixture in the bottle look now? ii. Do you see layers in it? iii. What is seen in the different layers from top to bottom? 15

16 Std. VI: General Science Workbook 2. Try this. (Textbook pg. no. 7) Obtain specimens of soil from various places in your surroundings such as your own yard, a garden, hills, river banks, fields and rocky ground. Note the differences in the specimens with respect to colour, feel, texture and the size of the particles. Type of soil Characteristics Colour Yard Garden Hills River Bank Fields Rocky ground Texture Size of particles *3. Obtain detailed information about the work of the India Meteorological Department. *4. Find a remedy for water scarcity. Grades: A - Excellent Teacher s Remark: B - Good C - Fair Date: Sign: