Chemistry In Everyday Life
Class 8 | Science — Chemistry | Unit 15
Class 8 Unit 15 Science
Unit 15: Chemistry in Every Day Life
Learning Objectives
After the completion of this lesson, students will be able to:
- know about different types of hydrocarbons.
- understand the formation of fossil fuels.
- list out the properties and uses of different fuel gases.
- understand the process involved in the refining of petroleum.
- know about the types and uses of coal.
- know about the characteristics of ideal fuel.
- list out the applications of solar energy.
Introduction
When we hear the word chemistry we think of chemical reactions conducted in the laboratories. But chemistry is beyond that. We can find chemistry in everything in our surrounding. It is in the air we breathe, the food we eat and in everything we use in our daily life. Our body is made of elements like nitrogen, phosphorous, hydrogen, oxygen, calcium, potassium, sulphur, magnesium etc. All the chemical reactions taking place in our body are due to chemistry. Our whole life is dependent on various chemical compounds. Among them, hydrocarbons are the most important one. They find application in our daily life. We can say that the whole civilization is driven by hydrocarbons because they make up the fossil fuels petroleum, coal and natural gas. In this lesson we are going to study about different types of hydrocarbons, fossil fuels like petroleum, coal and natural gas, characteristics of fuel and solar energy and its applications.
15.1 Hydrocarbons
Hydrocarbons are the organic compounds consisting of carbon and hydrogen atoms. They are combustible and produce large amount of heat energy along with carbon dioxide and water vapour, on burning. Hence, many hydrocarbons are used as fuels.
15.1.1 Sources of Hydrocarbons
Hydrocarbons occur naturally and they are found in fossil fuels like crude oil, natural gas and coal. About 300 million years ago plants and animals died and they were buried on the ocean floor. Overtime they were covered by silt and soil layers. Then they were buried deep inside the earth and compressed through temperature and pressure and converted to fossil fuels like oil and natural gas. These fuels are found in porous rocks which lie below large bodies of water, especially oceans. By drilling these rocks hydrocarbons can be extracted. Hydrocarbons are present in different trees and plants also.
15.1.2 Properties of Hydrocarbons
Among all the chemical compounds hydrocarbons have some unique properties. Some of them are given below.
- Most of the hydrocarbons are insoluble in water.
- Hydrocarbons are less dense than water. So they float on top of water.
- Most hydrocarbons react with oxygen to produce carbon dioxide and water.
- Hydrocarbons can be gases (Example methane and propane), liquids (Example hexane and benzene) or waxes (paraffin).
- Hydrocarbons are capable of making bonds with one another. This property is known as catenation (chain formation). Due to this property they form more number of complex molecules.
15.1.3 Types of Hydrocarbons
In hydrocarbons carbon and hydrogen atoms are linked together through different chemical bonds. Depending on the bond between these atoms there are number of hydrocarbons. The four general classes of hydrocarbons are: alkanes, alkenes, alkynes and arenes. Some of the common hydrocarbons are methane, ethane, propane, butane and pentane.
Methane is the simplest hydrocarbon in which four hydrogen atoms are linked with one carbon atom. It is a colourless, odourless and inflammable gas. It is an eco-friendly fuel because it does not produce any harmful products. It is used as a fuel in electricity generation. Methane is also known as marsh gas as it is present in marshes. Dead and decaying plants and animals release methane gas. It is a renewable source of energy. Sewage sludge can also be decomposed by microorganisms to produce methane gas along with impurities like carbon dioxide and hydrogen sulphide. After removing these impurities, methane gas can be used as an efficient fuel.
Propane is an odourless and highly inflammable gas. It is heavier than air. It is liquefied through pressurisation and commonly used as LPG (Liquefied Petroleum Gas) along with butane. Propane is used as fuel in heating, cooking and vehicles. Propane can also be used as refrigerants.
Activity 1
Make a model using clay and match sticks for the following hydrocarbons
Do You Know?
Propane is used in LPG cylinders. Since it is an odouress gas, any leakage cannot be detected. Hence, a chemical by name Mercaptan is mixed with LPG to help in detection of any leakage of LPG
Butane is a gas at room temperature and atmospheric pressure. They are highly flammable, colorless gases that quickly vaporize at room temperature. Butane is used as a fuel gas and propellant in aerosol sprays such as deodorants. Pure forms of butane can be used as refrigerants. Butane is also used as lighter fuel for a common lighter or butane torch.
Pentanes are liquids with low boiling point. They are used as fuels and solvents in the laboratory. They are also used to produce polystyrene.
15.2 Natural Gas
Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane along with other higher alkanes and a small percentage of carbon dioxide, nitrogen and hydrogen sulphide (H₂S). If the natural gas contains lower hydrocarbons like methane and ethane, it is called dry gas. If higher hydrocarbons like propane and butane are also present in the gas, it is called wet gas. Natural gas is always found above the oil in the oil wells. This gas is trapped inside the small spaces in underground rocks called reservoirs. Conventional natural gas can be extracted through drilling wells. Natural gas can also be found in reservoirs with oil and is extracted along with oil. This is called associated gas. Natural gas is a fossil fuel used as a source of energy for heating, cooking and electricity generation. Natural gas occurs in Tripura, Rajasthan, Maharashtra, Andhra Pradesh (Krishna, Godavari Basins) and Tamil Nadu (Cauveri Delta). It is also formed by the decomposition of organic matter in marshy areas and waste sewages. The natural gas formed by this way contains mainly methane.
Activity 2
Take a glass bottle and put some leaves, twigs, waste paper and saw-dust in it. Pour some water in it and keep it for 20 days. Open the bottle and bring a glowing splinter near the mouth. You can see a gas burning near the mouth showing its combustible nature. It is due to the evolution of natural gas.
15.2.1 Uses of Natural Gas
- Natural gas is used as an industrial and domestic fuel.
- It is used in thermal power stations.
- It is used as fuel in vehicles as an alternative for petrol and diesel.
- When heated it decomposes and forms hydrogen and carbon. Hydrogen thus formed is used in the manufacture of fertilizers.
- It is used to manufacture chemicals, fabrics, glass, steel, plastics and paints.
- It is also used in electricity generation.
Do You Know?
Moderate temperature and humidity is needed to keep paintings and other ancient artifacts from being destroyed by environmental factors. Thus natural gas is used in museums to protect the monuments.
15.2.2 Advantages of Natural Gas
- It produces lot of heat as it can be easily burnt.
- It does not leave any residue.
- It burns without smoke and so causes no pollution.
- This can be easily supplied through pipes.
- It can be directly used as fuel in homes and industries.
15.2.3 Compressed Natural Gas
When the natural gas is compressed at high pressure, it is called Compressed Natural Gas (CNG). Nowadays it is used as fuel in automobiles. The primary hydrocarbon present in CNG is methane (88.5%). Natural gas is liquefied for shipping in large tankers. This is called Liquefied Natural Gas (LNG). CNG is stored at high pressure whereas LNG is stored in ultra-cold liquid form. CNG has the following properties.
- It is the cheapest and cleanest fuel.
- Vehicles using this gas produce less carbon dioxide and hydrocarbon emission.
- It is less expensive than petrol and diesel.
More to Know
The average composition of CNG:
| Constituents | Percentage |
|---|
| Methane | 88.5 |
| Ethane | 5.5 |
| Propane | 3.7 |
| Butane | 1.8 |
| Pentane | 0.5 |
15.3 Other Gases
Apart from natural gas, there are some other gases which are used as fuel. Producer gas, coal gas, bio gas and water gas are some of them.
Producer Gas
Producer gas is a gaseous mixture of carbon monoxide and nitrogen. It is produced by passing air mixed with steam, over red hot coke at a temperature of 1100°C. It is used as an industrial fuel for iron and steel manufacturing.
Do You Know?
Producer gas is known by different names in different countries. It is referred as Wood gas in USA and as Suction gas in UK.
Coal Gas
It is a mixture of gases like hydrogen, methane and carbon monoxide obtained by the destructive distillation of coal. Heating coal in the absence of air is called destructive distillation. It is used in heating open hearth furnace in the manufacture of steel. It is also used as a reducing agent in certain metallurgical operations.
Water Gas
It is a gaseous mixture of carbon monoxide and hydrogen. It is made by passing steam over incandescent coke at a temperature of 1000°C.
C + H₂O → CO + H₂
It is also called as syngas or synthesis gas as it is used to synthesize methanol and simple hydrocarbons. It is used as an industrial fuel also.
Bio-Gas
Bio-gas is a mixture of methane and carbon dioxide. It is produced by the decomposition of plant and animal waste which form the organic matter. The breaking down of organic matter in anaerobic condition (ie., in the absence of oxygen) leads to the formation of biogas. It is an example for renewable source of energy.
Activity 3
Visit a bio-gas plant in your area with your teacher. Find out how it is prepared. Discuss about the uses and advantages of bio gas. In what way it will be helpful to the people in rural area?
15.4 Coal
Coal is one of the fossil fuels. It is a mixture of free carbon and compounds of carbon containing hydrogen, oxygen, nitrogen and sulphur. Three hundred million years ago, some plants grew into giant ferns and mosses. These plants got buried into the bottom of the soil. They slowly started to decompose and formed a dense, sponge like material called peat. Over time peat was compressed due to high temperature and pressure and coal was formed. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonization.
15.4.1 Extraction of Coal
Coal is extracted from the coal beds found below the surface of the earth. Coal found inside the earth is broken into pieces by explosives and brought above. Depending on the depth of the coal bed, coal is extracted in two ways.
Surface mining
If the coal beds lie within 22 feet of the earth's surface, the top soil is removed and coal is dug out. This is called surface mining
Underground mining
In some places, coal beds are found very deep inside the earth. In that case underground tunnels are made to get this coal. This is called underground mining or deep mining.
Coal reserves can be found in about 70 countries worldwide. The largest coal reserves are available in United State, Russia, China, Australia and India. The US is the international leader in coal reserves, with nearly 30% of the world's supply. Coal mining was started in India in 1774. India now ranks third among the coal producing countries in the world. USA and China have two third of the world's coal reserve.
15.4.2 Types of Coal
Coal is classified into four main categories based on the amounts of carbon it contains and the heat energy it can produce. They are lignite, sub bituminous, bituminous and anthracite. Among these four types anthracite is the most desirable one due to its high heat content.
Lignite
Lignite is a brown colored coal of lowest grade. It has the lowest carbon content. The carbon content of lignite is 25 to 35 percentage. Lignite contains a high amount of water and makes up almost half of our total coal reserves. It is used for electricity generation. The other uses include generating synthetic natural gas and producing fertilizer products.
Sub-bituminous
When lignite becomes darker and harder over time sub-bituminous coal is formed. Sub bituminous coal is a black and dull coal. It has higher heating value than lignite and contains 35 to 44 percentage carbon. It is used primarily as fuel for electricity power generation. This coal has lower sulphur content than other types and burns cleaner.
Bituminous
With more chemical and physical changes, sub-bituminous coal is developed into bituminous coal. Bituminous coal is dark and hard. It contains 45 to 86 percentage carbon. It has high heating value. It is used to generate electricity. Other important use of this coal is to provide coke to iron and steel industries. By-products of this coal can be converted into different chemicals which are used to make paint, nylon, and many other items.
Anthracite
Anthracite is the highest grade coal. It has a very light weight and the highest heat content. Anthracite coal is very hard, deep black and shiny. It contains 86 to 97 percentage carbon and has a heating value slightly higher than bituminous coal. It burns longer with more heat and less dust.
Activity 4
In an outline map of India mark the places where coal mines are found. Also identify the type of coal found in those areas.
15.4.3 Uses of Coal
- Coal is used to generate heat and electricity.
- It is used to make derivatives of silicon which are used to make lubricants, water repellents, resins, cosmetics, hair shampoos, and toothpaste.
- Activated charcoal is used to make face packs and cosmetics.
- Coal is used to make paper.
- Coal helps to create alumina refineries.
- Carbon fibre which is an extremely strong but light weight material is used in construction, mountain bikes, and tennis rackets.
- Activated carbon, used in filters for water and air purification and in kidney dialysis machines is obtained from coal.
15.4.4 Products obtained from coal
Coal when heated in the absence of air does not burn but produces many by-products. This process of heating coal in the absence of air is called destructive distillation of coal. The destructive distillation of coal can be carried out in the laboratories. The apparatus is as shown in Figure 15.13. Finely powdered coal is taken in a test tube and heated. At a particular temperature coal breaks down to produce coke, coal tar, ammonia and coal gas. Coal tar is deposited at the bottom of the second test tube and coal gas escapes out through the side tube. Ammonia produced is absorbed in the water, forming ammonium hydroxide. Finally a black residue called coke is left in the tube.
Thousands of different products have coal or coal by-products as their components. Some of them are soap, aspirins (tablet), solvents, dyes, plastics, and fibres, such as rayon and nylon. The main by products obtained during destructive distillation are coke, coal tar, ammonia and coal gas.
Coke
Coke contains 98% carbon. It is a porous, black and the purest form of coal. It is a good fuel and burns without smoke. It is largely used as a reducing agent in the extraction of metals from their ores. It is also used in making fuel gases like producer gas and water gas.
Coal tar
Coal tar is a mixture of different carbon compounds. It is a thick, black liquid with unpleasant smell. The fractional distillation of coal tar gives many chemical substances like benzene, toluene, phenol and aniline. They are used in the preparation of dyes, explosives, paints, synthetics fibers, drugs, and pesticides. Another product obtained from coal tar is naphthalene balls which are used to repel moth and other insects.
Coal gas
Coal gas also known as town gas is mainly a mixture of gases like hydrogen, methane and carbon monoxide. The gases present in coal gas are combustible and hence, it is an excellent fuel. It has high calorific value.
Ammonia
The other by product obtained from coal is ammonia. It is used for making fertilizers such as ammonium sulphate, ammonium superphosphate etc.
Do You Know?
It is also known as Black Diamond owing to its precious nature. On destructive distillation, 1000 kg of coal gives 700 kg of coke, 100 litres of ammonia, 50 litres of coaltar and 400 m³ of coal gas.
15.5 Petroleum
The term 'petroleum' is derived from the latin words 'petra' meaning rock and 'oleum' meaning oil. It is a fossil fuel formed from the remains of ancient marine organisms through decaying process. Petroleum is a complex mixture of hydrocarbons that occur in Earth in liquid, gaseous, or solid form. The term petroleum commonly denotes the liquid form, crude oil. But technically petroleum also includes natural gas and bitumen, a solid form. The natural gas and the crude oil constitute the primary fossil fuels.
Do You Know?
People in ancient cultures used crude oil for binding materials. It was also used as a sealant for waterproofing various surfaces.
15.5.1 Occurrence of Petroleum
The chief petroleum producing countries are U.S.A, Kuwait, Iraq, Iran, Russia and Mexico. In India, petroleum is found in Assam, Gujarat, Maharashtra (Mumbai), Andhra Pradesh (Godavari and Krishna basin) and Tamil Nadu (Cauveri Basins). By drilling through the earth the crude oil is pumped out from the well as a black liquid.
Do You Know?
The first oil well in the world was drilled in Pennsylvania, USA in 1859. The second oil well was drilled in Makum, Assam, India in 1867.
15.5.2 Refining of crude petroleum
The crude petroleum obtained from the well is a dark coloured viscous liquid which contains many impurities such as water, solid particles and gases like methane and ethane. To make it useful for different purposes, it must be separated into various components. The process of separating petroleum into useful by-products and removal of undesirable impurities is called refining. The steps involved in this process are given below.
Separation of water
The crude oil obtained from the oil wells will have salt water mixed with it. As the first step the water is removed from the crude oil.
Removal of sulphur compounds
The crude oil will have harmful sulphur compounds as impurities. In this step these impurities are removed.
Fractional distillation
Petroleum is a mixture of various constituents such as petroleum gas, petrol, diesel, kerosene, lubricating oil, paraffin wax, etc. The process of separation of various constituents or fractions of petroleum is done by fractional distillation in fractionating columns. The process of heating a mixture of liquids having different boiling points and then separating them by cooling is called fractional distillation. Crude petroleum is first heated to about 400°C in a furnace. As the vapours of crude oil move up the tower, the various fractions condense according to their boiling point ranges. The various fractions of petroleum obtained are given in Figure 15.17.
Many useful substances are obtained from petroleum and natural gas. These are termed as 'petrochemicals'. These are used in the manufacture of detergents, fibres, and other man-made plastics like polythene. Hydrogen gas obtained from natural gas, is used in the production of fertilizers. Due to its great commercial importance, pertoleum is also called 'black gold'.
15.5.3 Uses of Petroleum
Products obtained from crude oil have a number of uses.
- Liquefied Petroleum Gas or LPG is used in houses as well as in the industry.
- Diesel and petrol are used as fuels for vehicles. It is also used to run electric generators.
- Petrol is used as a solvent for dry cleaning.
- Kerosene is used as a fuel for stoves and also in jet planes.
- Lubricating oil reduces wear and tear and corrosion of machines.
- Paraffin wax is used to make candles, ointments, ink, crayons, etc.
- Bitumen or asphalt is mainly used to surface roads.
Activity 5
Find out where petroleum is extracted on a large scale in India. Also list out the petroleum refineries in India.
15.6 Fuel
Any substance that can produce heat and energy on burning is called fuel. We use this heat for various purposes such as cooking, heating and many industrial and manufacturing purposes. Some of the fuels that we use in our daily life are wood, coal, petrol, diesel and natural gas.
15.6.1 Types of fuel
Fuels are classified into different types according to their physical state. They are classified into solid, liquid and gaseous fuels.
Solid fuels
Fuels like wood and coal are in solid state and they are called solid fuels. This type of fuel was the first one to be used by man. These fuels are easy to store and transport. The production cost is also very low.
Liquid fuels
Most of the liquid fuels are derived from the fossil remains of dead plants and animals. Petroleum oil, coal tar and alcohol are some of the liquid fuels. These fuels give more energy on burning and burn without ash.
Gaseous fuel
Coal gas, oil gas, producer gas and hydrogen are some of the gaseous fuels. These fuels can be easily transported through pipes and they do not produce pollution.
15.6.2 Characteristics of fuel
An ideal fuel should have the following characteristics.
- It should be readily available
- It should be easily transportable
- It should be less expensive
- It should have high calorific value
- It should produce large amount of heat
- It should not leave behind any undesirable substances
15.6.3 Efficiency of Fuel
Any fuel contains carbon as its main constituent. During the combustion of fuel carbon combines with oxygen and liberates large amount of heat. It is expected that a fuel liberates maximum amount of heat in the short time. The efficiency of a fuel can be understood from the following terms.
Specific Energy
Specific energy is the amount of energy produced by unit mass of a fuel. It is defined as the energy per unit mass. It is used to measure the stored energy in certain substances. Its unit is J kg⁻¹.
Calorific Value
It is the quantity of heat produced by the complete combustion of fuel at constant pressure and normal conditions. It is measured in terms of KJkg-1.
Table 15.1 Calorific value of some fuels
| Fuel | Calorific Value (KJ/kg) |
|---|
| Cow dung cake | 6000 to 8000 |
| Wood | 17000 to 22000 |
| Coal | 25000 to 33000 |
| Petrol | 45000 |
| Kerosene | 45000 |
| Diesel | 45000 |
| Methane | 50000 |
| CNG | 50000 |
| LPG | 55000 |
| Biogas | 35000 to 40000 |
| Hydrogen | 150000 |
Octane Number
Octane number denotes the amount of octane present in petrol. The fuel having high octane number is called as an ideal fuel.
Cetane Number
Cetane number measures the ignition delay of the fuel in diesel engine. When cetane number is higher the ignition delay is shorter. The fuel with high cetane number is called as the ideal fuel.
Table 15.3 Difference between Octane number and Cetane number
| Octane Number | Cetane Number |
|---|
| Octane rating is used for petrol | Cetane rating is used for diesel |
| It measures the amount of octane present in petrol. | It measures the ignition delay of the fuel in diesel engine |
| Octane number of petrol can be increased by adding benzene or toluene. | Cetane number of diesel can be increased by adding acetone |
| The fuel with high octane number has low cetane number | The fuel with high cetane number has low octane number |
15.7 Alternative Fuel
The natural resources in the world have been used by man in a rapid way and they will be exhausted soon. The traditional fuel that we use today including petroleum are non renewable and they would be depleted soon. It is estimated that coal will last for 148 years, petroleum for 40 years and natural gas for 61 years. So we need to find alternative sources of energy. More over fossil fuels emit harmful gases like carbon dioxide, carbon monoxide and sulphur dioxide which pollute the atmosphere. Burning fossil fuels also cause temperature rise in the earth's atmosphere. Many believe that fuel which does not cause pollution is needed to enhance the quality of our environment. Some of the alternative fuels are given below.
Bio diesel
Bio diesel is a fuel obtained from vegetable oils such as soya bean oil, jatropha oil, corn oil, sunflower oil, cotton seed oil, rice-bran oil and rubber seed oil.
Do You Know?
Hydrogen - The future fuel
Hydrogen could be the best alternative fuel in the future. It is a clean fuel as it gives out only water while burning. Moreover, it has the highest energy content. It does not pollute air.
Wind energy
Wind energy is obtained with the help of wind mills. When wind blows, they rotate the blades of the wind mills and electricity is produced by the dynamo. Wind mills are mostly located at Kayathar, Aralvaimozhi, Palladam and Kudimangalam in Tamil Nadu.
Gobar Gas
Gobar gas is obtained by the fermentation of cow dung in the absence of air (anaerobic conditions). It mainly contains methane and a little ethane. It is widely used in rural areas for cooking and operating engines.
15.8 Solar Energy
Sun is the first and foremost energy source that makes life possible on the earth. Solar energy is the only viable fuel source of non depleting nature for sun provides a free and renewable source of energy. It is the renewable type of energy without endangering the environment. It is the potential source to replace the fossil fuel in order to meet the needs of the world. With the advancements in science and technology, solar energy has become more affordable, and it can overcome energy crisis. Solar energy is a clean energy. With the minimum efforts maximum energy can be harnessed using various equipments.
15.8.1 Applications of Solar Energy
Solar energy has wider applications in various fields.
- It is used in solar water heater.
- It is used in drying of agricultural and animal products.
- It is used in electric power generation.
- It is used in solar green houses.
- It is used in solar pumping and solar distillation.
- It is used for solar cooking and solar furnaces also.
Points to Remember
- Methane is the simplest hydrocarbon in which four hydrogen atoms are linked with one carbon atom.
- Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane.
- CNG is the cheapest and cleanest fuel. Vehicles using this gas produce less carbon dioxide and hydrocarbon emission. It is less expensive than petrol and diesel.
- Producer gas is a gaseous mixture of carbon monoxide and nitrogen.
- Water gas is a gaseous mixture of carbon monoxide and hydrogen. It is also called as syngas or synthesis gas.
- The term 'petroleum' is derived from the latin words 'petra' meaning rock and 'oleum' meaning oil.
- Any substance that can produce heat and energy on burning is called fuel.
- Specific energy is defined as the energy per unit mass. It is used to measure the stored energy in certain substances. Its unit is Jkg-1.
- Cetane number measures the ignition delay of the fuel in diesel engine.
- Solar energy is the energy derived from the sun in the form of solar radiation.
GLOSSARY
Bio Gas - Mixture of the gases methane and carbon dioxide. Calorific Value - The quantity of heat produced by the complete combustion of fuel at constant pressure and normal conditions. Catenation - The property of carbon atom to form bonds with itself resulting in a single large structure or chain. CNG - Compressed natural gas obtained at high pressure. Destructive distillation - The process of heating coal in the absence of air. Fractional distillation - The process of heating a mixture of liquids having different boiling points and then separating them by cooling. Hydrocarbons - Organic compounds consisting of hydrogen and carbon atoms. LPG - Liquefied Petroleum Gas Octane Number - The number which denotes the amount of octane present in petrol. Water Gas - Gaseous mixture of carbon monoxide and hydrogen.
TEXTBOOK EXERCISES
Exercise 1. Choose the best answer.
1. The chemical mixed with LPG that helps in the detection of its leakage is ___
a. methanol b. ethanol c. camphor d. mercapton
2. Which is known as syn gas?
a. Marsh gas b. Water gas c. Producer gas d. Coal gas
3. The unit of calorific value of fuel is ___
a. KJ mol⁻¹ b. KJ g⁻¹ c. KJ kg⁻¹ d. J kg⁻¹
4. ___ is the coal of superior quality.
a. Peat b. Lignite c. Bituminous d. Anthracite
5. The main component of natural gas is ___
a. methane b. ethane c. propane d. butane Exercise 2. Fill in the blanks.
1. Producer gas is a mixture of and
2. is known as marsh gas.
3. The term petroleum means
4. Heating coal in the absence of air is called
5. An example for fossil fuel is
Exercise 3. Match the following
| Octane rating | |
| Cetane rating | |
| Simplest hydrocarbon | |
| Peat | |
| Lignite | |
Options: Diesel, Methane, Petrol, Brown in colour, First stage coal
Exercise 4. Answer briefly.
1. What do you mean by catenation?
2. Mention the advantages of natural gas.
3. Expand CNG. List out its uses.
4. Identify the gas known as syngas. Why is it called so?
5. Anthracite is known as the highest grade coal. Give reason
6. Distinguish between octane number and cetane number.
7. Name the places in Tamil nadu harnessing wind energy from wind mills.
8. Solar energy is a non depleting energy. Justify.
Exercise 5. Answer in detail.
1. Explain the different types of coal.
2. What is known as destructive distillation? Write about the products obtained from fractional distillation of petroleum.
3. Explain the different types of fuel gases.
REFERENCE BOOKS
- Chemistry in daily life by Kirpal Singh.
- Chemistry in action: The molecules of everyday life by Nina Morgan.
- Engineering Chemistry by Dr.A. Ravi krishnan.
INTERNET RESOURCES
- www.learnchem.net
- https://edu.rsc.org/resources
📝 Summary
- Hydrocarbons are organic compounds consisting of carbon and hydrogen atoms that are combustible and produce large amounts of heat energy, making them useful as fuels in our daily life.
- Fossil fuels like crude oil, natural gas and coal were formed about 300 million years ago when plants and animals died, were buried on ocean floors, and converted through temperature and pressure over time.
- Hydrocarbons have unique properties including being insoluble in water, less dense than water, capable of reacting with oxygen to produce carbon dioxide and water, and can exist as gases, liquids or waxes.
- There are four general classes of hydrocarbons - alkanes, alkenes, alkynes and arenes - with common examples including methane, ethane, propane, butane and pentane.
- Methane is the simplest hydrocarbon with four hydrogen atoms linked to one carbon atom, is eco-friendly, used for electricity generation, and can be produced from decomposing sewage sludge and organic matter.