Text Book Back Questions and Answers - Chapter 15 Chemistry in Everyday Life 8th Science Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Text BookExercise : Chapter 15 Chemistry in Everyday Life Samacheer Kalvi Solutions Class 8 Science
I. Choose the best answer:
Question 1.
The chemical mixed with LPG that helps in the detection of its leakage is
(a) methanol
(b) ethanol
(c) camphor
(d) mercapton
Answer:
(d) mercapton

Question $2 .$
Which is known as syn gas?
(a) Marsh gas
(b) Water gas
(c) Producer gas
(d) Coal gas
Answer:
(b) Water gas
 

Question $3 .$
The unit of calorific value of fuel is
(a) kilo joule per mole
(b) kilo joule per gram
(c) kilo joule per kilo gram
(d) joule per kilo gram
Answer:
(c) kilo joule per kilo gram

Question $4 .$

______is the coal of superior quality.
(a) Peat
(b) Lignite
(c) Bituminous
(d) Anthracite
Answer:
(d) Anthracite
 

Question $5 .$
The main component of natural gas is
(a) methane
(b) ethane
(c) propane
(d) butane
Answer:
(a) methane
 

II. Fill in the blanks:

1. Producer gas is a mixture of............
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............
Answer:
1. Carbon monoxide and nitrogen
2. Methane
3. Rock oil
4. Destructive distillation
5. Coal

III. Match the following:
Question $1 .$
1. Octane rating - (a) Diesel
2. Cetane rating - (b) Methane
3. Simplest hydrocarbon - (c) Petrol
4. Peat - (d) Bown in colour
5. Lignite - (e) First stage coal
Answer:
1. c
2. a
3. b
4.e
5. d
 

IV. Answer briefly:
Question $1 .$
What do you mean by catenation?
Answer:
The property of carbon atom to form bonds with itself resulting in a single large structure or chain is called catenation.

Question $2 .$
Mention the advantages of natural gas.
Answer:
1. It produces lot of heat as it is easily burnt.
2 . It does not leave any residue.
3. It bums without smoke and so causes no pollution.
4. This can be easily supplied through pipes.
5 . It can be directly used as fuel in homes and industries.
 

Question $3 .$
Expand CNG. List out its uses.
Answer:
CNG - Compressed Natural Gas.
1. It is the cheapest and cleanest fuel.
2. Vehicles using this gas produce less carbon dioxide and hydrocarbon emission.
3. It is less expensive than petrol and diesel.

Question $4 .$
Identify the gas known as syngas. Why is it called so?
Answer:
Water Gas 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.
 

Question $5 .$
Anthracite is known as the highest grade coal. Give reason.
Answer:
1. Anthracite is the highest grade coal.
2. It has a very light weight and the highest heat content.
3. Anthracite coal is very hard, deep black and shiny.
4 . It contains $86-97 \%$ carbon and has a heating value slightly higher than bituminous coal.
5 . It bums longer with more heat and less dust.
 

Question $6 .$
Distinguish between octane number and cetane number.
Answer:
Octane Number:
1. Octane rating is used for petrol
2. It measures the amount of octane present in petrol
3. Octane number of petrol can be increased by adding benzene or toluene.
4. The fuel with high octane number has low cetane number
Cetane Number:
1. Cetane rating is used for diesel
2. It measures the ignition delay of the fuel in diesel engine.
3. Cetane number of diesel can be increased by adding acetone.
4. The fuel with high cetane number has low octane number

Question $7 .$
Name the places in Tamilnadu harnessing wind energy from wind mills.
Answer:
Wind mills are mostly located at Kayathar, Aralvaimozhi, Palladam and Kudimangalam in Tamil Nadu.
 

Question $8 .$
Solar energy is a non-depleting energy. Justify.
Answer:
1. Solar energy is the only viable fuel source of non - depleting nature for, Sun provides a free and renewable source of energy.
2. It is the renewable type of energy without endangering the environment.
3. 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.
 

V. Answer in detail:
Question $1 .$
Explain the different types of coal.
Answer:
Lignite:

1. Lignite is a brown coloured coal of lowest grade.
2. It has least content of carbon. The carbon content of lignite is $25-35 \%$.
3. Lignite contains a high amount of water and makes up almost half of our total coal reserves.
4. It is used for electricity generation.
5. It is used to generate synthetic natural gas and produce fertilizer products.
Sub-bituminous:
1. When lignite becomes darker and harder over time, sub-bituminous coal is formed.
2. Sub-bituminous coal is a black and dull coal.
3. It has higher heating value than lignite and contains $35-44 \%$ carbon.
4. It is used primarily as fuel for electricity power generation.
5. This coal has lower sulfur content than other types and bums cleaner.
Bituminous:
1. With more chemical and physical changes, sub-bituminous coal is developed into bituminous coal.
2. It is dark and hard. It contains $45-86 \%$ carbon. It has high heating value.
3. It is used to generate electricity.
4. Other important use of this coal is to provide coke to iron and steel industries.

Question $2 .$
What is known as destructive distillation? Write about the products obtained from petroleum.
Answer:
Coal when heated in the absence of air does not bum but produces many by-products.
This process of heating coal in the absence of air is called destructive distillation of
coal.
Products obtained from petroleum:
1. Liquefied Petroleum Gas or LPG
2. Diesel and petrol
3. Kerosene
4. Lubricating oil
5. Paraffin
6. Bitumen or asphalt
7. Refinery Gas
8. Naphtha
9. Fuel Oil
10. Chemicals
11. Jet fuel
12. Waxes
13. Polishes
 

Question $3 .$
What are the different types of fuels?
Answer:
Fuels are classified into solid, liquid and gaseous fuels according to their physical state. Solid fuels:

1. Fuels like wood and coal are in solid state and they are called solid fuels.
2. This type of fuel was the first one to be used by man.
3. These fuels are easy to store and transport.
4. The production cost is also very low.
Liquid fuels:
1. 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.
2. These fuels give more energy on burning and bum without ash.
Gaseous fuel:
1. Coal gas, oil gas, producer gas and hydrogen are some of the gaseous fuels,
2. It can be easily transported through pipes and they do not produce pollution.

AdditionalQuestions
I. Choose the correct answer:
Question $1 .$
Dead and decaying plants and animals release _______ gas.
(a) propane
(b) butane
(c) methane
(d) pentane
Answer:
(c) methane
 

Question $2 .$
_______is an odourless and highly inflammable gas.

(a) Propane
(b) Butane
(c) Ethane
(d) Methane
Answer:
(a) Propane
 

Question $3 .$
Which gas is used as fuels and solvents in the laboratory?

(a) Natural gas
(b) $\mathrm{CNG}$
(c) Methane
(d) Butane
Answer:
(d) Butanel
 

Question $4 .$
Which of the following is referred as wood gas?
(a) Water gas
(b) Producer gas
(c) Coal gas
(d) None
Answer:
(b) Producer gas
 

Question $5 .$
Which is used in museums to protect the monuments?
(a) CNG
(b) Producer Gas
(c) Water gas
(d) Natural gas
Answer:
(d) Natural gas

Question $6 .$
________is a mixture of methane and carbon dioxide.
(a) Bio-gas
(b) Water gas
(c) Coal gas
(d) None
Answer:
(a) Bio-gas

Question $6 .$
________is a mixture of methane and carbon dioxide.
(a) Bio-gas
(b) Water gas
(c) Coal gas
(d) None
Answer:
(a) Bio-gas

Question $7 .$
_______is a gaseous mixture of carbon monoxide and hydrogen.

(a) Bio-gas 
(b) Natural gas
(c) Water gas
(d) Producer gas
Answer:
(b) Natural gas
 

Question $8 .$
The breaking down of organic matter in an anaerobic condition leads to the formation of $\ldots . . \ldots . \ldots . \ldots . . .$
(a) coal gas
(b) natural gas
(c) bio-gas
(d) $\mathrm{CNG}$
Answer:
(c) Bio-gas

Question $9 .$
When lignite becomes darker and harder over time ________ coal is formed.
(a) lignite
(b) bituminous
(c) anthracite
(d) sub-bituminous
Answer:
(d) sub-bituminous
 

Question $10 .$
Which one among the following is an extremely strong but lightweight material is used in mountain bikes and tennis rackets?
(a) Cotton fibre
(b) Carbon fibre
(c) Plastic fibre
(d) None
Answer:
(b) Carbon fibre
 

II. Fill in the blanks:

1. Hydrogen gas obtained from natural gas is used in the production of________
2. Hydrocarbons are present in different ________ and________
3. Hydrocarbons are less dense than________
4. Sewage sludge can also be decomposed by microorganisms to produce methane gas along with impurities like carbon dioxide and________
5 . ________ can also be used as refrigerants.

$6 .$ ________ is used as a fuel gas and propellant in aerosol sprays such as deodorants.
$7 .$ ________ natural gas can be extracted through drilling wells.
$8 .$ ________ coal is a black and dull coal.
9 ________ is used to make face packs and cosmetics.
10. Activated carbon used in filters for water and air purification and in _______ machines is obtained from coal.

Answer:
1. fertilizers
2. trees, plants
3. water
4. hydrogen sulphide
5 . Propane
6. Butane
7. Conventional
8. Sub-bituminous
9. Activated charcoal
10. kidney dialysis
 

III. Write true or false- if false, write the correct statement:
Question $1 .$
Coal helps to create alumina refineries.
Answer:
True
 

Question $2 .$
Coke is used in the preparation of dyes, explosives, paints synthetic fibers and pesticides.
Answer:
False
Correct statement:
Coal tar is used in the preparation of dyes, explosives, paints, synthetic fibers and pesticides.
 

Question $3 .$
Coal is also known as black diamond owing to its precious nature.
Answer:
True

Question $4 .$
Crude oil is used as a sealant for waterproofing various surfaces.
Answer:
True
 

Question $5 .$
The process of separating petroleum into useful by-products and removal of undesirable impurities is called distillation.
Answer:
False
Correct statement:
The process of separating petroleum into useful by-products and removal of undesirable impurities is called refining.
 

IV. Match the following:
Question $1 .$
1. Hydrocarbons - (a) Marsh gas
2. Methane - (b) Cleanest fuel
3. Butane - (c) Catenation
4. CNG - (d) Polystryrene
Answer:
1. $\mathrm{c}$
2. a
3. $d$
4. $\mathrm{b}$
 

V. Short answer questions:
Question $1 .$
Write any 2 properties of hydrocarbons.
Answer:

1. Most of the hydrocarbons are insoluble in water.
2. Hydrocarbons are less dense than water. So they float on top of water.
3. Most hydrocarbons react with oxygen to produce carbon dioxide and water.
 

Question $2 .$
Write the uses of natural gas.
Answer:
1. Natural gas is used as an industrial and domestic fuel.
2 . It is used in thermal power stations.
3. It is used as fuel in vehicles as an alternative for petrol and diesel.
 

Question $3 .$
Write a note on bio-gas.
Answer:
1. Bio-gas is a mixture of methane and carbon dioxide.
2. It is produced by the decomposition of plant and animal waste which form the organic matter.
3. The breaking down of organic matter in anaerobic condition (ie., in the absence of oxygen) leads to the formation of biogas.
4. It is an example for renewable source of energy.

Question $4 .$
What is surface mining?
Answer:
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.
 

Question 5.
What is deep mining?
Answer:
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.
 

Question $6 .$
Write a note on coke.
Answer:
1. Coke contains $98 \%$ carbon. It is porous, black and the purest form of coal.
2. It is a good fuel and burns without smoke.
3. It is largely used as a reducing agent in the extraction of metals from their ores.
4. It is also used in making fuel gases like producer gas and water gas which is a mixture of carbon monoxide and hydrogen.

Question 7.
What are the characteristics of fuel?
Answer:
1. It should be readily available.
2. It should be easily transportable
3. It should be less expensive
4. It should have high calorific value
5 . It should produce large amount of heat
6. It should not leave behind any undesirable substances.
 

Question $8 .$
Write a note on bio - diesel.
Answer:
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.
 

VI. Long Answer type Questions:
Question $1 .$
What are the uses of coal?
Answer:
1. Coal is used to generate heat and electricity.
2. It is used to make derivatives of silicon which are used to make lubricants, water repellents, resins, cosmetics, hair shampoos and toothpaste.
3. Activated charcoal is used to make facepacks and cosmetics.
4. It is used to make paper.
5. It helps to create alumina refineries.
6. Carbon fibre is an extremely strong but lightweight material is used in construction, mountain bikes, and tennis rackets.
7. Activated carbon used in filters for water and air purification and in kidney dialysis machines is obtained from coal.

Question $2 .$
Explain destructive distillation of Coal.
Answer:
1. The destructive distillation of coal can be carried out in the laboratories.
2. 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 first tube.