Living Science 2020 2021 Solutions for Class 8 Science Chapter 5 - Coal And Petroleum

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Resources that helped life to originate and survive on the earth are:
(i) Air
(ii) Water
(iii) Soil
(iv) Minerals.

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Yes, natural resources are both living and non-living.
Living natural resources are plants and animals.
Non-living natural resources are air, water, soil, and minerals.

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Yes, groundwater is a renewable source. But today we are using it more than it is renewing, so the water level is decreasing day by day.

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As the population on earth is increasing day by day, therefore their requirements are also increasing. So, more resources are used day by day. It affects the number of natural resources available to them.

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Three fuels obtained by digging into the earth are:
(i) Petrol    (ii) LPG    (iii) Kerosene

They all are commonly known as petroleum.
 
They are so called because they are obtained from underground rocks. They are a mixture of several hydrocarbons.
  
 

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Yes, all fossil fuels are composed of hydrocarbons i.e. carbon and hydrogen. Fossil fuels were formed as a result of plants or animals that died millions of years ago and were buried inside the earth for a long period of time. Over millions of years, heat and pressure changed the dead organisms into fossil fuels. As the most abundant elements in the living organisms(Plants or animals) are carbon and hydrogen, that's why all fossil fuels are made up of compounds of carbon and hydrogen. 

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Coke is a better fuel because it is almost the purest form of carbon. It burns without the smoke and has a high calorific value.

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As the number of carbon atoms increases, the boiling point also increases. This property is used to separate petroleum into its various fractions.

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CNG is compressed natural gas. Advantages of CNG over petrol and diesel is that CNG is a non-polluting fuel for vehicles.

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(d) all of these
Renewable resources need to be conserved because non-renewable resources such as coal, petroleum and natural gas take millions of years to form naturally. Moreover, they cannot be replaced as quickly as they are being consumed.

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(d) residue
Residue is that component of petroleum which is collected at the bottom of the tower. It can be further distilled separately to obtain lubricating oil and paraffin wax. 

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(a) carbon
Coal is mainly composed of carbon. It may also contain varying amounts of hydrogen, oxygen, nitrogen and sulphur.

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(c) anthracite
Anthracite coal has the highest carbon content and is the cleanest form of coal.

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(d) CNG
CNG is a natural gas stored under high pressure. Burning of natural gas produces nitrogen oxides, sulphur dioxide, carbon dioxide and carbon monoxide in low quantities than that produced during the burning of coal or oil. Thus, it is a non-polluting fuel.

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(b) 1000°C
In destructive distillation of coal, coal is heated at 1000°C in the absence of air to produce coal tar, coal gas, coke and liquor ammonia as main by products.

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(c) electricity
Electricity is generated by man using natural resources; therefore, it is not a natural source of energy.

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(d) non-renewable and cannot be recycled
Fossil fuels are non-renewable and cannot be recycled because they are formed extremely slowly (in millions of years) from dead remains of living organisms and their rate of consumption is more than their rate of replenishment.

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(d) Hydrogen

Fossil fuels are the fuels that are formed naturally from the dead remains of living organisms in millions of years. They include natural gas, petroleum and coal.

Hydrogen is not a fossil fuel because it is not formed by a natural process.

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(b) Coal gas
In destructive distillation of coal, coal is heated at high temperature in the absence of air to produce coal tar, coal gas, coke and liquor ammonia as its main by-products.

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Natural resources are both living and non-living.
Natural resources refers to resources that are present in our nature, gifted by God and can be freely used, for example, soil, air, sunlight, water, plants, animals etc.

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True. Although petroleum is a renewable resource, its regeneration takes millions of years. Its rate of depletion is much higher than its rate of formation. As we have limited sources of petroleum, we should use it judiciously.

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The process of conversion of wood into coal is called carbonisation.

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Anthracite is the variety of coal with maximum carbon content.

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Petroleum and natural gas were formed from dead remains of living organisms. 

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In fractional distillation, hydrocarbons with the lowest boiling points condense first.

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1. LPG: Liquefied petroleum gas is a non-poisonous colourless gas, commonly known as cooking gas. It can be stored in cylinders and is drawn out and used as gas.

2. Kerosene: Kerosene is a flammable pale yellow or colourless oily liquid with a non pleasant odour. It is used as a fuel in lamps and domestic heaters or furnaces.

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Kerosene is used as a fuel in jet aeroplanes.
Kerosene is a flammable pale yellow or colourless oily liquid with a unpleasant odour. It is obtained from petroleum.

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Compressed Natural Gas (CNG) is a non-polluting fuel for vehicles. Burning of natural gas produces nitrogen oxides, sulphur dioxides, carbon dioxide and carbon monoxide in very small amounts. Thus, it does not cause pollution.

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Petroleum, also called crude oil, is a thick dark coloured oily liquid. Most of the chemicals present in crude oil are slightly colourless or yellow except bitumen, which brings dark color to crude oil.  

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Bitumen is an oil-based substance and is used for surfacing roads. It is a semi solid product obtained from the refining of petroleum.

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Paraffin wax, a white or colourless soft solid extracted from petroleum, is used to manufacture candles, vaseline, grease and polish.

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Solar energy is the ultimate source of the energy for fossil fuels.
Plants absorb sun's energy through photosynthesis when they are alive and the animals that eat them, get the energy from plants. This energy stays trapped in them for millions of years and gets converted into fuel. Thus, the energy released when fuel is burnt, originally comes from the sun.

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The fuel obtained from coal that is almost pure form of carbon is coke.

Coke is a fuel with high carbon content and few impurities. It is made from destructive distillation of coal.

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Fuels that are formed from the dead remains of living organisms by natural processes are called fossil fuels. They take millions of years to form.
Petroleum, coal and natural gas are fossil fuels, which are formed after dead remains of living organisms get buried under the sea and earth through natural processes like compression.

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Fossil fuels such as coal, petroleum and natural gas take millions of years to form naturally. They cannot be replaced as fast as they are being consumed. Moreover, it is not possible to make new fossil fuels artificially. If they are overused, they will get exhausted as they are available in nature in limited amount. That is why, they should not be wasted.

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Coke is a hard porous black substance which is obtained by destructive distillation of coal.

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Following are the advantages of using natural gas as a fuel:
1. It is easy to transport through pipes and cylinders.
2. It does not cause pollution on usage.
3. It can be directly burnt in homes and factories for cooking and other purposes.

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There is a rapid increase in our energy consumption because of the following reasons:

1. World’s population is increasing, which means energy requirements are also increasing. People need more energy to cook food, to heat their homes etc., which means more energy is being used.
2. With the development of countries, energy consumption also increases because people use more devices which need energy, both for functioning and manufacturing.

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Matter that stores energy is called fuel. 
We depend most on fossil fuels for many energy uses because fossil fuels can be burnt, shipped and stored. The energy from fossil fuels is both concentrated and portable. Fossil fuel releases tremendous amount of energy on burning. Natural gas provides cleaner burning and coal is available in abundance.

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Petroleum or crude oil is a complex mixture of organic liquids. Crude oil is of little use in industrial applications.
Petroleum refining is done to convert crude oil into more useful products such as petrol, kerosene, LPG, diesel, waxes, asphalt etc.

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A renewable resource is any resource that can "renew" itself within a person's life span. But most renewable resources become exhaustible if we use them faster than they are renewed or replaced by nature.

Examples:
Ground water is a renewable resource. In recent years, there is a decline in its level because its usage is faster than its replacement. This has led to the drying of wells.

Forests or trees are being cut down to fulfil our need of wood for furniture, paper etc. It usually takes 25 years or more for a tree to grow to its original state. If new trees do not grow up and replace the older trees as fast as the older trees are cut down, sooner or later they would be exhausted.  

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Topsoil is considered a non-renewable resource because its rate of erosion is faster than its rate of regeneration. Although topsoil does build up over time through weathering of rocks and minerals and decaying of organic matter, it does not build up to an appreciable amount in a person's lifetime.

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Our ancestors had modest energy requirements, mostly for cooking, lighting and heating. In today's society, energy consumption by humans has increased manyfold as compared to energy consumed by early humans because people have progressed. Developed nations use more energy especially for transportation and industry. Most of the energy we use today comes from fossil fuels which are non-renewable on a human time scale.
That is why, there is more need for energy conversation today than early times.

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Coal was formed by the dead remains of the plants by the process of carbonisation. Millions of years ago, dead flora and fauna in forests got buried under soil, rocks and other land masses due to earthquakes, volcanic eruptions and floods. With the passage of time, more soil layers got deposited on it and they were compressed and went deeper and deeper beneath the earth. This raised the temperature and pressure beneath the soil. This initiated the process of burning these dead remains. Slowly, all the vegetation got converted into coal, which is a rich form of carbon.

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Uses of coke:

1. It is used in industries for manufacturing of steel and for the extraction of many metals.
2. It is used in thermal power plants to produce electricity.
3. It is used as a domestic fuel for cooking and heating.

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Petroleum was formed by the dead remains of the sea animals which got trapped under soil and clay and more deposits were formed with time. Due to depth, the temperature and pressure raised and over the years, they got converted into petroleum oil. Since, oil is lighter than water, it did not mix with water and arose to the superficial rocks, which did not allow it to pass through them.

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Various constituents of petroleum oil obtained during fractional distillation in oil refineries are:

1. Liquid Petroleum Gas (LPG): It is primarily used as domestic fuel. Now, it is also used as fuel in vehicles and industry because it is less polluting and easy to transport.
2. Petrol: It is a black liquid used as fuel in light vehicles like scooters, cars, etc. It is also used as aviation fuel and for dry cleaning of fabrics.  
3. Kerosene: It is used as fuel in stoves, lamps and jet aircrafts.
4. Diesel: It is used as fuel for heavy vehicles and electric generators. 

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Advantages of judicious use of energy:

1. Fossil fuels are primary source of energy today. If they are used indiscriminately, they will be exhausted because they are available in limited amount. It takes millions of years to form fossil fuels and it is not possible to make new fossil fuels artificially. Therefore, they should be wisely used and not wasted.
2. Judicious use of energy today will help future generations to use the available resources.

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Destructive distillation of coal is carried out by heating coal strongly to 1000°C in the absence of air. When coal is heated without air, it does not burn but breaks down to produce following by-products:

(a) Coke: It is used in industries for manufacturing of steel and extraction of many metals. It is used as a domestic fuel for cooking and heating.

(b) Coal tar: It can be used to make soap, fats, dyes, plastics perfumes, drugs, pesticides, explosives etc.

(c) Coal gas: It is used as fuel in coal processing plants and in various other industrial units situated near coal processing plants.

(d) Ammonia: It is used for making nitrogenous fertilisers.

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Refining of petroleum is carried out by fractional distillation of crude oil.



Process of fractional distillation of crude oil is as follows:

• Crude petroleum is heated and converted into gas.
• The gases enter the bottom of a long column (fractional distillation column), which is filled with trays or plates.
• The gases rise in the column, and gets cooled and condenses when they reach their boiling points
• The trays collect various liquid fractions which may pass to the condensers, which cool them further and go to the storage tanks.
• The small chains, usually gaseous molecules, come out at the top, while the liquid medium chain molecules come out at the middle and the solid remains at the bottom.

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Following ways and measures can help in preventing an energy crisis:

1. Vehicles should be driven at constant and moderate speed.
2. Engines should be switched off at traffic lights and other temporary halts.
3. Vehicle pooling can reduce number of vehicles plying on road, which, in turn, will lead to less consumption of fuel.
4. At home, gas stoves should be cleaned properly and burners should not be left burning unnecessarily.

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CNG is obtained from the deposits of natural gas close to the earth’s surface (usually dwarfed by nearby oil deposits). Deeper deposits formed at higher temperatures and under more pressure have more natural gas than oil. Once the natural gas reserve is discovered, it is extracted from the ground by a pipeline and sent to power plants, factories and processing plants. Here, it is cleaned, separated and converted into CNG (by storing under high pressure), a usable fuel for homes and businesses.

Uses  of CNG:
1. It is very easy to transport through pipes and cylinders.
2. It does not cause pollution on usage, while other petrochemicals like petrol and diesel do.
3. It can be directly used in homes and factories for cooking and other purposes.

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If a resource can be replaced within ten years by natural processes, it can be classified as renewable. Renewable resource is a resource that can renew itself within a person's life span, while a non-renewable resource takes millions of years to form.

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Renewable resources are resources that are present in infinite amounts (for example, the sun, wind) and can be replaced or reproduced at a scale comparable to its consumption (for example, wood because we can plant trees).

All renewable resources are inexhaustible, i.e., last forever with limited use.
But most renewable resources become exhaustible if we use them faster than they are renewed or replaced by nature.

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Fuel is a substance which on burning releases a large amount of energy as heat at a reasonable cost and leaves behind little ash content. For example, coal, natural gas, petroleum nearly meet all these conditions.
Combustible substance is the one which liberates heat on burning. The amount of heat liberated is different for different substances. This determines whether or not a substance is a good fuel.
All the combustible substances are not fuels because many of them produce less amount of heat for a particular amount of energy input on burning and leave behind high ash content; for example, paper, cloth, etc. 

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Fossil fuels can’t be prepared in our laboratory because it took millions of years for dead bodies of plants and animals to get converted into fossil fuels. Moreover, necessary conditions of high temperature and pressure for the conversion of dead bodies into fossil fuel cannot be created in a laboratory.

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Conservation of resources means not only avoiding their wasteful use but also maintaining their quality. It can also be defined as restoring, protecting and maintaining the natural ecosystem, vegetation and wildlife.

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Following two properties of petroleum make it possible to form a layer of it above water:

1. Petroleum is immiscible with water, i.e., it cannot be mixed with water. 
2. Petroleum oil is lighter than water, it forms a layer above water.

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Yes, coal and petroleum products are used in the production of electricity. Which runs the electrical appliances at Salma's home. As coal and petroleum are non-renewable sources i.e. once they are used, they cannot be replaced. So, if we use coal and petroleum excessively then a point of time may come when it will not be available at all, which can create a crisis of electric energy. That's why Salma tries to save electricity, which can eventually save coal and petroleum.