Samacheer Kalvi 8th Science Unit 15 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 15 – Chemistry In Everyday Life Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 15 Answers are given below.

Science Book Back Answers

Unit 15 – Chemistry In Everyday Life

I. 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
Answer: (d) mercapton

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

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

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

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:

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.

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.

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.

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.

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.

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

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.

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.

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