Science textbook solutions for Class 7 science Chapter 16 Natural Resources

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Important points to remember :

  1. Metals are obtained  from their ore by extraction and purification. Impurities of  sand and  soil in an  ore are called  ‘gangue’. 
  2. Resources in the earth’s crust include minerals,  ores, mineral  oil and other fuels, rocks, water, elements,  etc.     
  3. A  majority  of the metals occur in the form of compounds. Minerals that contain a high  proportion  of metal  are called  ores. 
  4. Some important minerals like diamond, ruby, sapphire, emerald, jade, zircon are used as gems. Gems are in great demand. 
  5. Deposits of common salt are also found in the earth. This salt is called rock salt. It is used in food and in some medicines. 
  6. Coal is found in mines. Peat, lignite  (brown coal), bituminous  coal and anthracite are the various types of coal. 
  7. Anthracite is the coal of  the highest grade. 
  8. The Oil and Natural Gas Corporation (ONGC) was established on  14th August 1956. Fossils  are the preserved remains of  dead  organisms  in  rock.  
  9. Fossils are the signs of their  existence left  behind by organisms that got buried billions of years ago.

Question 1: Describe natural resources with reference to the following  three types.

a) Mineral resources
Answer : Mineral wealth has an important place among natural resources. Minerals are formed by various processes taking place  in the environment. The  rocks on the  earth  are mainly  made  of minerals. These minerals can be obtained  by mining. Only a  few metals  like,  for  example,  gold, silver,  copper, platinum  and bismuth  occur  in the free state in nature. A  majority  of the metals occur in the form of compounds. Minerals that contain a high  proportion  of metal  are called  ores. It is economical  to obtain metals from ores. The properties of  minerals  become clear from  their characteristic colour, lustre, hardness, shape (length), cleavage  or fracture  and streak.

1. Iron  ore :  Iron occurring in the impure state is called  iron ore. Iron ore is used to make  a variety of articles from pins to heavy machinery. For  example, farming implements, rails of  railway tracks, etc. The four main ores of iron are magnetite, haematite, limonite and  siderite. 2. Manganese :  Manganese occurs in  the  form of its carbonate, silicate  and oxide. Compounds of manganese are used in the preparation of medicines and for giving  a pink  tinge to glass. Manganese is also used in electrical  appliances. 3. Bauxite :  Bauxite is the most important ore of aluminium.  It contains 55% aluminium.  Bauxite consists mainly of aluminium oxide. Aluminium is a  very  good  conductor  of  electricity  and  heat.  Its density is low

b) Forest resources
Answer : An extensive area of land covered by a variety of plants is called a forest.  A  forest  is a natural  habitat  of plants, animals and microbes.  About 30% of the total land of the world is covered by forests. Forests perform certain specific protective and productive functions.

Wood :  We get strong and durable wood as also firewood  from trees  like teak, mahogany, neem,  acacia, subabhul. Wood  is used  for making furniture, farming implements and various other articles as well as in construction work.

c) Ocean resources 
Answer : Energy can be obtained on a large scale from oceans. Sea waves  at high and low tide and ocean currents are being used for generation of power. Last year, we have learnt something about this in Geography.  There are reserves of a  variety of natural resources in seawater, at the bottom of the sea  and beneath the seabed, too. These resources available  from seas and oceans are called  marine  resources. There  are  large  scale  reserves of mineral  oil and natural gas at the bottom  of sea. We avail of these by drilling  oil and gas wells.
Mineral resources from oceans Thorium  – used in the production of atomic energy. Magnesium – used in the  flash bulb of a camera. Potassium –  the main ingredient in production of soap, glass, fertilizer. Sodium – used in the production of cloth and paper. Sulphate – used in making artificial silk.

Question 2: Write answers to the following questions in your own words .

a) What is meant by fossil fuel? What are their types ?
Answer : Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth’s crust over hundreds of millions of years. There are three types of fossil fuels which can all be used for energy provision; coal, oil and natural gas. Coal is a solid fossil fuel formed over millions of years by decay of land vegetation. When layers are compacted and heated over time, deposits are turned into coal.

Natural gas is a gaseous fossil fuel that is versatile, abundant and relatively clean compared to coal and oil. Like oil, it is formed from the remains of marine microorganisms. It is a relatively new type of energy source.

Oil is a liquid fossil fuel that is formed from the remains of marine microorganisms deposited on the sea floor.

b) Make a list of the components we obtain from mineral oil.
Answer : List of Components we obtain from Mineral oil:

Baby oil. Baby lotions. Cold creams. Ointments. Cosmetics. Can be used as transformer oil in transformers. Spindle oil which acts as lubricant in textile industry. Break fluid in some cars and bikes disc brakes.

c) What do we get from forests ?
Answer : We get rubber from the trees in the forest which is very useful in making daily essentials like tyres. Sponges: Sponges are obtained from renewable plant-based materials such as cotton fiber and wood pulp.

d) What are the items included in ocean resources? What are their uses?
Answer : Ocean resources provide jobs, goods and services for billions of people around the world and have immense economic importance. There resources include food, fuel, renewable energy, minerals, sand and gravel and tourism.

e) Why should we prevent the wastage of fuel used for vehicles?
Answer : To prevent fuel we should use more public transport, CNG gas engine vehicles and other electric vehicles to prevent more fuel for next generation. … so by every small and better means, nowadays, fuel wastage is protected

f) Why is the diversity of plants and animals in the forests declining?
Answer : Biodiversity decline continues due to a rapidly expanding human population. Habitat is damaged in order to meet growing needs for agriculture, urban development, water and materials. Fish, wildlife and plants are overharvested, despite mounting evidence that many harvesting practices are unsustainable.

g) Write the names of five minerals and the useful substances obtained from them.
Answer :
1. Coal.
It is known as the Black gold and very useful for the generation of the Electricity, ammonia, Sulphur tar, etc.

2. Iron ore.
It is one of the Minerals found in India and Useful fir the Iron and the Steel Industries in India. Iron ore is also used for making some medicines and the great use of it is involved in the transportation.

3. Manganese.
This minerals are used for making the Dry cells and also used in strengthen the Iron in Industries.

4. Bauxite.
It is the Ore of the Aluminum which is used for the transportation, and also used in the Electrical Industries as it is the good conductors of the Electricity.

5. Petroleum.
It is known as the liquid gold and used for the Power generation and also used for making fuel which are used for transportation.

h) Name the two important stages in the process of obtaining  metals from ores ? 
Answer : Answer: Metals are obtained from their ore by extraction and purification. Most of the metals are harvested from the underground mines. And in the initial stage various impurities are also mixed with the metals,and with these impurities the metals are known as the ores.

Question 3: What steps taken for protection and conservation of natural resources ?
Answer : Natural resources are utilized by human beings either directly or indirectly for survival. The examples of natural resources are air, soil, water, sunshine, coal, plants, animals, and minerals. Additionally, nature acts as the sole provider for our fundamental needs which includes food, clothing and shelter.

Environment education must be imparted by including the same in the curricula of the schools. National Parks are making an effort for the safety of the natural resources. By reducing, reusing and recycling of non-renewable resources. Non-human species must be disturbed only to meet the basic needs. Planting of more and more trees to save our forest resources. Seeking alternatives to non-renewable resources. By increased use of bio-gas and bio-fuels.

Question 4: Complete the flow chart .
Answer :

Question 5: How does the economic condition of  a nation depend on its natural resources ?
Answer : Answer: The principal factor affecting the development of an economy is the natural resources or land. “Land” as used in economics includes natural resources such as the fertility of land, its situation and composition, forest wealth, minerals, climate, water resources and sea resources etc.

Question 6: Which medicinal plants will you grow on your school premises and near your house? Why?
Answer : The following medicinal plants can be grown in the school as they are easily available, easy to maintain and have various health benefits:​

Cinchona − Quinine, a drug used in the treatment of malaria, is obtained from the bark of the Cinchona tree.

Eucalyptus − The leaves of eucalyptus are used for extracting on oil which is used in the treatment of blocked nose and throat infections.

Neem – Neem leaf is used for leprosy, eye disorders, bloody nose, intestinal worms, stomach upset, loss of appetite, skin ulcers, diseases of the heart and blood vessels (cardiovascular disease), fever, diabetes, gum disease (gingivitis), and liver problems. The leaf is also used for birth control and to cause abortions.

Cinnamon –
Cinnamon Is High in a Substance With Powerful Medicinal Properties. Cinnamon Is Loaded With Antioxidants. Cinnamon Has Anti-Inflammatory Properties. . Cinnamon May Cut the Risk of Heart Disease.Cinnamon Can Improve Sensitivity to the Hormone Insulin. Cinnamon Lowers Blood Sugar Levels and Has a Powerful Anti-Diabetic Effect.

#let’s recall 
1. What is meant  by natural resources? 
Answer : A resource is a source or supply from which a benefit is produced. Resources can broadly classified upon their availability—they are classified into renewable and non renewable resources.

2.Give some examples  of natural resources.
Answer : A natural resource is what people can use which comes from the natural environment. Examples of natural resources are air, water, wood, oil, wind energy, natural gas, iron, and coal. The dividing line between natural resources and man-made resources is not clear-cut.

# Use your brain power 
1. Why are all minerals not ores ? 
Answer : All ores are minerals while all minerals are not ores as some of them might have a large amount of unwanted substances such as sand, stones and earthly impurities. For example: Aluminium occurs in earth’s crust in the form of two minerals bauxite and clay.

2. What is meant by ‘metal mineral’  and ‘non-metal mineral’ ?
Answer : Metallic minerals are those minerals which can be melted to obtain new products. Examples of metallic minerals are iron, copper, bauxite, tin etc. Non-metallic minerals are those which do not yield new products on melting. They are not so hard and have no shine or luster of their own.

3. What is meant  by fuels? 
Answer : A fuel is a substance that is changed in some way to produce heat, electricity, or other forms of energy. This is usually by being burnt, although there are exceptions, such as nuclear fuel. Fuel can be divided into two main types: fossil fuels and other fuels.

4. Which  natural resources do we use as fuels?
Answer : Oil, coal, natural gas, metals, stone and sand are natural resources. Other natural resources are air, sunlight, soil and water. Animals, birds, fish and plants are natural resources as well. Natural resources are used to make food, fuel and raw materials for the production of goods.

5. Why is  mineral oil called ‘liquid gold’ ?
Answer : mineral is called liquid gold because of it’s high price and value and its economic need by all the countries worldwide. Because of its high price value and it’s economic need mineral oil is called liquid gold.

6.Why is coal called  ‘black gold’ ? 
Answer : Petroluem is known as black gold as it is black coloured crude oil that is extracted from earth’s crust and it has its value as it is limited in stock, takes millions of years to form and is costly available.

7. What would happen if underground  mineral resources are exhausted ?
Answer : These minerals are fastly used in many industrial sectors which manufacture products which we use in our daily life. If these minerals are exhausted ,our necessary products will become rarely available in the market which will ruin our human ecosystem.

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